Ocarina on Ocarina — manual

02.03.01 — The Result[T] type

Wed, 20 May 2026 00:00:00 +0000

02.03.01 — The `Result[T]` type#

Source file: src/ocarina/railway/result.py — zero dependencies.

Code#

from dataclasses import dataclass, field
from typing import TypeGuard, final


class _BaseResult:
    """Base class ensuring both Ok and Fail have error attribute for type narrowing."""
    error: Exception | None


@final
@dataclass(frozen=True)
class Ok[T](_BaseResult):
    value: T
    error: None = None


@final
@dataclass(frozen=True)
class Fail(_BaseResult):
    error: Exception = field(default_factory=lambda: Exception("Unknown error"))


type Result[T] = Ok[T] | Fail


def is_ok[T](result: Result[T]) -> TypeGuard[Ok[T]]:
    return isinstance(result, Ok)


def is_fail[T](result: Result[T]) -> TypeGuard[Fail]:
    return isinstance(result, Fail)

Six design decisions, dissected#

1. `_BaseResult` as a common parent#

class _BaseResult:
    error: Exception | None

One job: let mypy read result.error without narrowing first. Without the base, you’d have to write:

02.04.01 — The validate → assert_that → execute → raise_if_invalid flow

Wed, 20 May 2026 00:00:00 +0000

02.04.01 — The `validate → assert_that → execute → raise_if_invalid` flow#

Source file: src/ocarina/dsl/invariants/validate.py (entry-point) + src/ocarina/dsl/invariants/internals/validation_chain.py

The state machine#

Diagram#

validate(value: T)
       │
       ▼
ValidationStartBlock[T]
       │
       └─ assert_that(predicate, *, msg=None)
              │
              ▼
       ValidationAssertBlock[T]   ← state accepting several continuations
              │
              ├─► assert_that(P)     [loop, AND-chainable, see dedicated diagram]
              ├─► otherwise(P)       [OR, see 03-otherwise-any-of.md]
              ├─► then(U, name=...)  [value swap, see 04-then-chain-of-validations.md]
              └─► execute()          → _ValidationResult
                                          │
                                          ├─ is_valid: bool
                                          ├─ errors: Sequence[InvariantViolationError]
                                          ├─ validated_values: Sequence[Any]
                                          └─ raise_if_invalid() : None | raise AggregateInvariantViolationError

`assert_that` loop#

assert_that declares one assertion on the current value. Multiple assert_that calls chain — each adds another condition (logical AND, order preserved).

02.05.01 — Test[Driver]

Wed, 20 May 2026 00:00:00 +0000

02.05.01 — `Test[Driver]`#

Source file: src/ocarina/dsl/testing/oc_test.py

Signature#

@final
class Test[Driver]:
    def __init__(
        self,
        *,
        name: TestName,
        test_id: str | None = None,
        test_scenario: TestScenario[Driver],
        pre_test_scenarios_fragments: Sequence[TestScenarioFragment[Driver]] | None = None,
        post_test_scenarios_fragments: Sequence[TestScenarioFragment[Driver]] | None = None,
        skipped: bool = False,
    ) -> None:
        if test_id is None:
            test_id = name
        self.name = name
        self.test_id = test_id
        self._test_scenario = test_scenario
        self._pre_test_scenarios_fragments = pre_test_scenarios_fragments or []
        self._post_test_scenarios_fragments = post_test_scenarios_fragments or []
        self._skipped = skipped

Six parameters:

Parameter	Type	Role
`name`	`TestName` (`str`)	Human label; appears in the report, and becomes the log file name (hence subject to `is_valid_filename`).
`test_id`	`str \| None`	Stable identifier for `--only` / `--exclude`. If absent: takes `name`.
`test_scenario`	`TestScenario[Driver]` (alias = `Callable[[Driver, ILogger], Scenario[Driver]]`)	Factory that builds the `Scenario` at execution time.
`pre_test_scenarios_fragments`	`Sequence[TestScenarioFragment[Driver]] \| None`	`(driver, logger) -> TestChain` functions executed before the main scenario.
`post_test_scenarios_fragments`	`Sequence[TestScenarioFragment[Driver]] \| None`	`(driver, logger) -> TestChain` functions executed after the main scenario.
`skipped`	`bool`	If `True`, the test is registered but not executed.

1. `@final`#

No user inheritance. Want a “special” test? Compose via fragments or a scenario — don’t subclass.

02.10.01 — WebDriversPool[Driver]

Wed, 20 May 2026 00:00:00 +0000

02.10.01 — `WebDriversPool[Driver]`#

Source file: src/ocarina/infra/drivers_pool.py

Thread-safe driver pool, max concurrency enforced by semaphore, monitored async warmup, clean shutdown. No reuse — every acquire() disposes its driver on the way out (clean state).

Constructor#

@final
class WebDriversPool[Driver]:
    def __init__(
        self,
        create_driver: Thunk[BuiltWebDriver[Driver]],
        max_size: int,
        warmup_timeout: float | None = None,
    ) -> None:
        self._create_driver = create_driver
        self._pool: Queue[BuiltWebDriver[Driver]] = Queue(max_size)
        self._semaphore = Semaphore(max_size)
        self._warmup_timeout = (
            warmup_timeout if warmup_timeout is not None and warmup_timeout > 0.1
            else 60.0 * 5
        )

Primitive	Role
`Queue(max_size)`	Queue of pre-built available drivers.
`Semaphore(max_size)`	Guarantees that at most `max_size` drivers live simultaneously (whether queued or acquired).
`warmup_timeout`	Max no-progress delay during warmup before raising `WarmupTimeoutError`. Default 300s.

`acquire()`#

@contextmanager
def acquire(self) -> Iterator[Driver]:
    try:
        driver, dispose = self._pool.get_nowait()
    except Empty:
        self._semaphore.acquire()
        try:
            driver, dispose = self._create_driver()
        except Exception:
            self._semaphore.release()
            raise

    try:
        yield driver
    finally:
        with suppress(Exception):
            dispose()
        self._semaphore.release()

              acquire()
                  │
                  ▼
   ┌──────────────────────────────────┐
   │ pool.get_nowait()                │── OK ─► driver, dispose         ← warmup case
   └──────────────┬───────────────────┘
                  │ Empty
                  ▼
   ┌──────────────────────────────────┐
   │ sem.acquire()                    │  ← blocks if N drivers alive
   └──────────────┬───────────────────┘
                  ▼
   ┌──────────────────────────────────┐
   │ create_driver()                  │── raises ─► sem.release(); raise
   └──────────────┬───────────────────┘
                  ▼
   ┌──────────────────────────────────┐
   │ yield driver                     │  ← caller uses it
   └──────────────┬───────────────────┘
                  ▼
                finally :
                  with suppress : dispose()       ← driver disposed
                  sem.release()                   ← release a slot

1. No reuse#

Queue.get_nowait() consumes the entry. Once pulled, the driver never goes back. At the end (finally), it’s disposed.

02.11.01 — CliBuilder + CliArg + _SilentArgumentParser

Wed, 20 May 2026 00:00:00 +0000

02.11.01 — `CliBuilder` + `CliArg` + `_SilentArgumentParser`#

Source file: src/ocarina/opinionated/cli/builder.py

Declarative overlay on top of argparse. Aggregates validation errors, rewrites the help output on error, and registers post-parse effects.

`_SilentArgumentParser`#

class _SilentArgumentParser(ArgumentParser):
    def error(self, message: str) -> Never:
        """Raise an error."""
        raise ValueError(message)

The standard ArgumentParser calls sys.exit(2) directly on error. With that turd of a default, you can’t intercept and you can’t aggregate multiple errors.

_SilentArgumentParser reroutes errors as ValueError. So CliBuilder.parse can catch and aggregate them.

02.03.02 — The builder state machine

Wed, 20 May 2026 00:00:00 +0000

02.03.02 — The builder state machine#

Source file: src/ocarina/dsl/testing_with_railway/internals/action_chain.py

Here’s where the entire ROP mechanic lives: four successive typed states that literally (as in: the type-checker literally) refuse any syntactic improvisation. The DSL doubles as its own immune system.

Overview#

                      ┌─────────────────┐
   start(action)  →   │  ActionStart[T] │     an Action[T] = Thunk[Result[T]]
                      └────────┬────────┘
                               │ .failure(failure_handler)
                               ▼
                      ┌─────────────────┐
                      │ ActionFailure[T]│
                      └────────┬────────┘
                               │ .success(success_handler)
                               ▼
                      ┌─────────────────┐
                      │ ActionSuccess[T]│
                      └────────┬────────┘
                               │ .execute()   ── runs action(), fires the handler
                               ▼
                      ┌─────────────────┐
                      │ ActionChain[T]  │     holds (has_failed, result)
                      └──────┬──────────┘
                             │ .then(next_action_or_start)
              ┌──────────────┴──────────────┐
              │                             │
   has_failed=True                   has_failed=False
              │                             │
              ▼                             ▼
   ┌──────────────────┐         ┌───────────────────┐
   │ NeutralAction-   │         │ ActionStart[T]    │  → cycle starts over
   │ Start[T]         │         │  (the next action │
   │ (failure rail:   │         │   will execute)   │
   │  the whole chain │         └───────────────────┘
   │  becomes no-op,  │
   │  while keeping   │
   │  the fluent API) │
   └──────────────────┘
              │
              ▼ (.failure → .success → .execute, all no-op)
   ┌──────────────────┐
   │  ActionChain[T]  │   has_failed=True, result=<accumulated Fail>
   └──────────────────┘

The types `Action`, `FailureHandler`, `SuccHandler`#

type Action[T]        = Thunk[Result[T]]      # () -> Result[T]
type FailureHandler   = Callable[[Exception], None]
type SuccHandler      = Effect                # () -> None

Action[T] is a Thunk. Calling ActionStart(action) does not run anything. The action just gets captured.
FailureHandler gets the exception, not the Fail or the Result. Deliberate: 99% of handlers want to log the exception, take a screenshot, and move on.
SuccHandler is an Effect (no argument). Same idea — a success handler logs a static message, snaps a screenshot, doesn’t need the result.

Typestate Pattern: why you can’t get it wrong#

The chain is strictly linear. Each method returns a different type that only exposes the next legal step:

02.04.02 — Catalog of builtin assertions

Wed, 20 May 2026 00:00:00 +0000

02.04.02 — Catalog of builtin assertions#

Source file: src/ocarina/dsl/invariants/assertions.py — ~25 predicates.

Every assertion follows the same contract:

A direct predicate (value: T) -> None that raises InvariantViolationError on contract violation.
Or a closure when you need a config argument (is_equal_to(cmp), etc.).
Or, occasionally, a higher-order function (HOF) like each. Lives here pragmatically — a dedicated file for a single case would be overkill.

Full table#

Assertion	Direct / closure / HOF	Domain	Description
`is_str(value)`	direct	`Any`	Raises if `value` is not a `str`
`is_none(value)`	direct	`Any`	Raises if `value is not None`
`is_not_none(value)`	direct	`Any`	Raises if `value is None`
`is_equal_to(cmp)`	closure	`Any`	Returns `(value) -> None` that raises if `value != cmp`
`is_not_equal_to(cmp)`	closure	`Any`	Returns `(value) -> None` that raises if `value == cmp`
`is_less_than(cmp)`	closure	`float`	`value < cmp`
`is_less_than_or_equal_to(cmp)`	closure	`float`	`value <= cmp`
`is_greater_than(cmp)`	closure	`float`	`value > cmp`
`is_greater_than_or_equal_to(cmp)`	closure	`float`	`value >= cmp`
`is_positive(value)`	direct	`float`	`value >= 0`
`is_not_zero(value)`	direct	`float`	`value != 0`
`is_in(elements)`	closure	`Any`	`value in tuple(elements)`
`is_file(value)`	direct	`str \| Path`	`Path(value).is_file()`
`is_dir(value)`	direct	`str \| Path`	`Path(value).is_dir()`
`is_iso_date_string(value)`	direct	`str`	`datetime.fromisoformat(value)`
`is_iso_utc_date_string(value)`	direct	`str`	Checks ISO + `tzinfo == UTC`
`is_email(value)`	direct	`str`	No whitespace, exactly one `@`, non-empty parts, domain contains `.`
`has_unique_elements(*, key=None)`	closure	`Iterable[Any]`	Detects duplicates (raises `DuplicatesError`). Type-strict (`1 ≠ True`), supports unhashables.
`is_empty(value)`	direct	`Sized`	`len(value) == 0`
`is_truthy(value)`	direct	`Any`	`bool(value) is True`
`is_valid_filename(value)`	direct	`str`	Cross-platform: forbidden chars, Windows reserved words, no leading/trailing space or dot, length ≤ 255
`each(predicate)`	HOF	`Iterable[Any]`	Applies `predicate` to each element

A few implementations in detail#

`is_email`#

def is_email(value: str) -> None:
    """Assert that the string is a valid email address (fast check)."""
    if " " in value:
        raise InvariantViolationError(f"'{value}' must not contain whitespace.")
    if value.count("@") != 1:
        raise InvariantViolationError(f"'{value}' must contain exactly one '@' character.")
    local_part, domain_part = value.split("@")
    if not local_part or not domain_part:
        raise InvariantViolationError(f"'{value}' must have non-empty local and domain parts.")
    if "." not in domain_part:
        raise InvariantViolationError(f"Domain part of '{value}' must contain at least one '.'.")

Four bare-minimum checks. No RFC 5322 regex. Deliberate: real email validation happens by sending an email, not by regex.

02.05.02 — TestExecutor[Driver]

Wed, 20 May 2026 00:00:00 +0000

02.05.02 — `TestExecutor[Driver]`#

Source file: src/ocarina/dsl/testing/internals/test_executor.py

One job: run one attempt of a test with one driver. Knows nothing about retries, the driver pool, or suite-level aggregation.

`ExecutionOutcome`#

@final
@dataclass(frozen=True, slots=True)
class ExecutionOutcome:
    result: TestResult
    skipped: bool
    setup_failed: bool
    should_retry: bool
    steps_count: int

Field	Type	Meaning
`result`	`TestResult` = `Result[Any] \| None`	The chain’s result (Ok, Fail), or `None` if skip / setup_failed.
`skipped`	`bool`	True if `test_runner.skipped` (i.e. `Test(skipped=True)`).
`setup_failed`	`bool`	True if the scenario’s `setup()` raised.
`should_retry`	`bool`	True if the retry rule applies (transient_error detected).
`steps_count`	`int`	Number of `act` calls; `-1` if skip or setup_failed.

slots=True: blocks dynamic attribute addition, saves memory. This object rides the hot path — slots earns its keep.
frozen=True: immutable, safe to share across threads.
@final: no inheritance.

Execution order for one attempt#

┌──────────────────────────────────────────────────────────────────────┐
│  test_runner = test.spawn(driver, logger_with_taxonomy)              │
└──────────────────────────────┬───────────────────────────────────────┘
                               │
                               ▼
              ┌─────────────────────────────────┐
              │  test_runner.skipped ?          │── True ─► return Outcome(skipped=True, ...)
              └────────────────┬────────────────┘
                               │ False
                               ▼
              ┌─────────────────────────────────┐
              │  logger.test_name(test.name)    │   (annotation)
              └────────────────┬────────────────┘
                               │
                               ▼
              ┌─────────────────────────────────┐
              │  setup() (if not None)          │── raises ─► teardown() (if not None)
              └────────────────┬────────────────┘            ↓
                               │                  return Outcome(setup_failed=True, should_retry=True, ...)
                               ▼
              ┌─────────────────────────────────┐
              │  watchers.start(driver, logger, │
              │                 take_screenshot)│   (1 daemon thread per watcher)
              └────────────────┬────────────────┘
                               │
                               ▼
              ┌─────────────────────────────────┐
              │  _run_chain(chain_runners, ...) │── returns (result, should_retry)
              └────────────────┬────────────────┘
                               │
                               ▼
              ┌─────────────────────────────────┐
              │  watchers.stop()                │   (always)
              └────────────────┬────────────────┘
                               │
                               ▼
              ┌─────────────────────────────────┐
              │  teardown() (if not None)       │   (ALWAYS, even if chain failed)
              └────────────────┬────────────────┘     (exceptions are logged & swallowed)
                               │
                               ▼
              ┌─────────────────────────────────┐
              │  steps_count = act_counter.get()│
              │  return Outcome(...)            │
              └─────────────────────────────────┘

`execute`#

def execute(
    self, test: Test[Driver], *,
    driver: Driver,
    taxonomy: tuple[str, ...],
    logger_with_taxonomy: ILogger,
    logger_without_taxonomy: ILogger,
    attempt: int, max_attempts: int,
) -> ExecutionOutcome:
    test_runner = test.spawn(driver, logger_with_taxonomy)

    if test_runner.skipped:
        return ExecutionOutcome(result=None, skipped=True, setup_failed=False,
                                should_retry=False, steps_count=-1)

    logger_without_taxonomy.test_name(test.name)

    if test_runner.setup is not None:
        try:
            test_runner.setup()
        except Exception as exc:
            msg = f"{test.name} -- Setup failed (attempt {attempt}/{max_attempts}): {exc}"
            logger_with_taxonomy.warning(msg)
            if test_runner.teardown is not None:
                self._run_teardown(test_runner.teardown, test_name=test.name, logger=logger_with_taxonomy)
            return ExecutionOutcome(result=None, skipped=False, setup_failed=True,
                                    should_retry=True, steps_count=-1)

    watchers: Sequence[Watcher[Driver]] = test_runner.watchers or []
    self._start_watchers(watchers, driver=driver, test_name=test.name, taxonomy=taxonomy)

    result, should_retry = self._run_chain(
        test_runner.chain_runners, test_name=test.name, attempt=attempt,
        driver=driver, logger=logger_without_taxonomy,
        logger_with_taxonomy=logger_with_taxonomy, max_attempts=max_attempts,
    )

    self._stop_watchers(watchers)

    if test_runner.teardown is not None:
        self._run_teardown(test_runner.teardown, test_name=test.name, logger=logger_with_taxonomy)

    steps_count = self._act_counter.get()
    return ExecutionOutcome(result=result, skipped=False, setup_failed=False,
                            should_retry=should_retry, steps_count=steps_count)

Two loggers: why#

logger_with_taxonomy vs logger_without_taxonomy:

02.10.02 — DriverBuilder[Driver]

Wed, 20 May 2026 00:00:00 +0000

02.10.02 — `DriverBuilder[Driver]`#

Source file: src/ocarina/infra/driver_builder.py

Encapsulates profile handling (often a tmp copy of a user directory) and produces the (driver, dispose) pair the pool expects.

Why a builder?#

Building a Selenium driver with a profile requires:

Copy the profile to a temp folder (otherwise Firefox/Chrome locks the original).
Start the driver pointing at the temp folder.
At the end: driver.quit(), then delete the temp folder.

DriverBuilder factors out those three steps:

02.11.02 — CliStore[TKeys] + _CliField[T] + phantom_validate

Wed, 20 May 2026 00:00:00 +0000

02.11.02 — `CliStore[TKeys]` + `_CliField[T]` + `phantom_validate`#

Source files: src/ocarina/opinionated/cli/store.py, src/ocarina/opinionated/cli/phantoms.py

Write-once store for parsed CLI values. Each field validates on write. TKeys: Literal[...] gives key autocomplete.

`_CliField[T]` — write-once field#

class _CliField[T]:
    def __init__(self, *, validate: ValidationChainBuilder[T]) -> None:
        self._value: T | _Unset = _UNSET
        self._validate = validate

    def set(self, value: T) -> None:
        if not isinstance(self._value, _Unset):
            raise RuntimeError("Value already set.")
        self._validate(_validate(value)).execute().raise_if_invalid()
        self._value = value

    def get(self) -> T:
        if isinstance(self._value, _Unset):
            raise RuntimeError("Value not set yet.")
        return self._value

1. `_Unset` sentinel#

class _Unset:
    pass

_UNSET = _Unset()

Why not None? Because None can be a legitimate value (--profile-path isn’t mandatory; its post-parse value can legitimately be None). A dedicated sentinel separates “not set yet” from “set to None”.

02.03.03 — The failure rail: NeutralAction*

Wed, 20 May 2026 00:00:00 +0000

02.03.03 — The failure rail: `NeutralAction*`#

Edge case in the builder: what happens when you chain an action onto an ActionChain that has already failed?

Why Neutral classes rather than a user-side `if`#

When you chain an action onto an already-failed ActionChain, you slide into three Neutral classes that honor the same API but do nothing.

Picture the DSL without this. User code would look like:

chain = act1.failure(h).success(h).execute()

if chain.is_ok():
    chain = chain.then(act2).failure(h).success(h).execute()

if chain.is_ok():
    chain = chain.then(act3).failure(h).success(h).execute()

Imperative, unreadable, and the whole point of the DSL is gone. The neutral rail keeps the writing flat:

02.04.03 — .otherwise(...) and _any_of

Wed, 20 May 2026 00:00:00 +0000

02.04.03 — `.otherwise(...)` and `_any_of`#

How Ocarina expresses a logical OR between two predicates without breaking error aggregation.

The problem#

Concrete case: you want “age == 18 OR age <= 65.” The ROP/invariants syntax is a strict chain of assertions, and every .assert_that() is an AND. How do you express an OR?

Code#

def otherwise(self, fallback: Predicate[T], *, msg: str | None = None) -> ValidationAssertBlock[T]:
    if self._last_predicate is None:
        raise RuntimeError("otherwise() must follow assert_that().")

    fallback_with_msg = _with_msg(fallback, msg, self._name)
    combined = _any_of(
        self._last_predicate, *([*self._otherwise_predicates, fallback_with_msg])
    )
    self._chain._steps.pop()                    # replace the last step
    self._chain.add_assertion(self._value, combined, self._name)
    self._last_predicate = combined
    self._otherwise_predicates.append(fallback_with_msg)
    return self

Guard: otherwise() has to follow an assert_that(). With no prior predicate it raises. (In practice the type-checker already rules it out — ValidationStartBlock.otherwise doesn’t exist.)
Combination: combine previous predicate + all accumulated otherwise predicates + the new one, via _any_of. Result: a composite predicate.
Step replacement: pop the last step from _ValidationChain and push the combined one. Otherwise the original predicate AND the combined one would both be present, and the original error would resurface.

`_any_of`#

def _any_of[T](*predicates: _PredicateWithMsg[T]) -> _PredicateWithMsg[T]:
    def _try_predicate(p: _PredicateWithMsg[T], value: T) -> InvariantViolationError | None:
        try:
            p(value)
        except InvariantViolationError as exc:
            return exc
        else:
            return None

    def combined(value: T) -> None:
        errors = []
        for p in predicates:
            error = _try_predicate(p, value)
            if error is None:
                return                              # ✅ one predicate passes → all pass
            errors.append(error)

        formatted_error_messages = "  | " + "\n  | ".join(str(e) for e in errors)
        msg = (
            f"All predicates failed for value {value!r}.\n"
            "» At least one of the following conditions must be satisfied:\n"
            f"{formatted_error_messages}"
        )
        raise InvariantViolationError(msg)

    return _PredicateWithMsg(combined)

First success wins: the moment one predicate passes, combined returns None.
All fail: build an aggregated message listing every failure, separated by |.
Result is a _PredicateWithMsg: plug it back into the chain like any other predicate.
Aggregation is recursive: 3 successive otherwise() calls fold (P_orig OR P_otherwise1 OR P_otherwise2 OR P_otherwise3) into one predicate.

Example#

validate(age, name="age")
    .assert_that(is_equal_to(18), msg="Must be 18 or at most 65")
    .otherwise(is_less_than_or_equal_to(65), msg="Must be 18 or at most 65")
    .execute()
    .raise_if_invalid()

If age == 18: is_equal_to(18) passes → OK.
If age == 30: is_equal_to(18) raises, is_less_than_or_equal_to(65) passes → OK.
If age == 70: both raise → InvariantViolationError with:

age: All predicates failed for value 70.
» At least one of the following conditions must be satisfied:
  | age: Must be 18 or at most 65
  | age: Must be 18 or at most 65

(The duplicated message comes from passing the same msg= twice. Intentional here — we want a single statement of intent.)

02.05.03 — TestFlow[Driver] — retry policy

Wed, 20 May 2026 00:00:00 +0000

02.05.03 — `TestFlow[Driver]` — retry policy#

Source file: src/ocarina/dsl/testing/internals/test_flow.py

One job: for a single Test, run the retry loop, acquire a fresh driver per attempt, apply the backoff policy.

Why an intermediate level between `TestSuite` and `TestExecutor`#

Level	Doesn’t know about
`TestExecutor`	Retries, the driver pool
`TestFlow`	Inter-test concurrency, suite-level aggregation
`TestSuite`	One attempt’s execution, retries

A genuinely strict separation. TestFlow is the only level that knows both the pool and the retry policy — combining them is its whole job.

02.10.03 — Screenshotter[TDriver]

Wed, 20 May 2026 00:00:00 +0000

02.10.03 — `Screenshotter[TDriver]`#

Source file: src/ocarina/infra/screenshotter.py

Generic, thread-safe screenshot utility. Driver-agnostic via a Protocol, configurable via a dataclass. Supports burst.

`Protocol`#

class ScreenshotDriver(Protocol):
    def save_screenshot(self, path: str) -> bool:
        """Save standard viewport screenshot."""

That’s it. Any object with save_screenshot(path: str) -> bool qualifies. Selenium WebDriver has it natively (driver.save_screenshot), Playwright can be wrapped, a fake driver in tests exposes it trivially.

`ScreenshotterConfig[TDriver]`#

@dataclass(frozen=True)
class ScreenshotterConfig[TDriver: ScreenshotDriver]:
    output_dir: Path
    file_ext: str = ".png"
    health_check: HealthCheck[TDriver] | None = None
    save_full_page: SaveFullPageScreenshot[TDriver] | None = None
    default_burst_delay: float = 0.5
    max_filename_retries: int = 500
    uuid_length: int = 8

Field	Type	Role	Default
`output_dir`	`Path`	Screenshot directory	—
`file_ext`	`str`	Extension (`.png`, `.jpg`)	`.png`
`health_check`	`HealthCheck[TDriver] \| None`	`(driver) -> None` that raises if the driver is dead	`None`
`save_full_page`	`SaveFullPageScreenshot[TDriver] \| None`	`(driver, path) -> bool` for full-page screenshots (Firefox only)	`None`
`default_burst_delay`	`float`	Delay between 2 shots in burst mode	`0.5`s
`max_filename_retries`	`int`	Max attempts to generate a unique name	`500`
`uuid_length`	`int`	UUID suffix length in the name	`8`

Immutable. Configure once, ship.

02.11.03 — Auto CLI store + flags + validation

Wed, 20 May 2026 00:00:00 +0000

02.11.03 — Auto CLI store + flags + validation#

Source file: src/ocarina/opinionated/cli/selenium/create_cli_store.py

Flags#

Flag	Default	Type	Validation
`--driver-path`	`""`	`str`	`is_file` (except `--browser safari`)
`--profile-path`	`None`	`str`	`is_none` OR `is_dir`
`--browser`	`None` (required)	`str`	argparse `choices` (per OS)
`--not-headless`	`False` (= headless by default)	`bool` (`store_true`)	phantom
`--workers`	`5`	`int`	`is_positive` + `is_not_zero`
`--logger`	`"terminal+file"`	`str`	`choices=LOGGERS_CHOICES`
`--wait-timeout`	`10`	`int`	`≤ 60`, `> 0`
`--dont-force-delete-tmp-dirs`	`False`	`bool` (`store_true`)	phantom
`--only`	`[]`	`list[str]` (`nargs="+"`)	phantom + mutex
`--exclude`	`[]`	`list[str]` (`nargs="+"`)	phantom + mutex

_DEFAULT_WORKERS_AMOUNT = 5
_DEFAULT_LOGGER: SupportedLogger = "terminal+file"
_DEFAULT_BROWSER_AUTOMATION_TIMEOUT = 10
_MAX_BROWSER_AUTOMATION_TIMEOUT = 60

`Literal[...]`#

type SeleniumCliStoreKeys = Literal[
    "driver_path", "profile_path", "browser", "headless", "workers",
    "logger", "wait_timeout", "force_delete_tmp_dirs", "only", "exclude",
]

These keys are the store’s whole vocabulary. Call-sites use them: store.get("workers"), store.get("browser"), etc.

Chapter 02 — Ocarina, the framework

Wed, 20 May 2026 00:00:00 +0000

Chapter 02 — Ocarina, the framework#

Unpacks the whole ocarina framework (Python 3.14+, v1.1.10) and Railway Oriented Programming straight through to the reporting plugins. Structured as a layered walk: deepest (the Result[T] type) to most visible (the bootstrap that boots everything).

Chapter plan#

#	Subject	File or folder
01	Technical identity, dependencies, toolchain	`01-identity.md`
02	Full module tree + layered diagram	`02-module-tree.md`
03	Railway Oriented Programming	`03-railway/`
04	Invariants (validate, assertions, chain_validations)	`04-invariants/`
05	Orchestration (Test → TestSuite → TestCampaign → TestCycle)	`05-orchestration/`
06	Lifecycle of a `Scenario`	`06-scenario.md`
07	Watcher	`07-watcher.md`
08	`POMBase`	`08-pom-base.md`
09	Ports & adapters (`ILogger`, `ITakeScreenshot`)	`09-ports.md`
10	Infrastructure (pool, builder, screenshotter, act counter, Selenium adapters)	`10-infra/`
11	Opinionated layer (CLI, loggers, plugins, bootstrap)	`11-opinionated/`
12	Custom types & custom errors	`12-custom-types-errors.md`

Functional programming: ../03-functional/
How the framework tests itself: ../04-internal-tests/
Usage examples with project adapters: ../07-ocarina-example/, ../08-ai-example/
CI: ../10-cicd/02-ocarina-workflows.md

Chapter 02.03 — Railway Oriented Programming

Wed, 20 May 2026 00:00:00 +0000

Chapter 02.03 — Railway Oriented Programming#

Ocarina’s beating heart. The whole DSL rides on this mechanic: success and failure as two parallel rails. A failure switches the train onto the failure rail and locks it there (short-circuit), but composition stays linear so the scenario still reads top-to-bottom.

Plan#

#	File	Subject
01	`01-result.md`	`Result[T] = Ok[T] \| Fail`, `is_ok`/`is_fail`
02	`02-action-chain-states.md`	State machine `ActionStart → ActionFailure → ActionSuccess → ActionChain`.
03	`03-neutral-rail.md`	Failure rail: `NeutralActionStart` / `NeutralActionFailure` / `NeutralActionSuccess`.
04	`04-chain-actions-fold.md`	`ChainRunner[T]` (thunk) + `chain_actions` (fold).
05	`05-create-act-hooks.md`	`create_act` and its hooks (`on_failure`, `on_run_effect`, `act_counter_effect`).
06	`06-drive-page.md`	`drive_page`, a semantic alias.
07	`07-match-page-when.md`	`match_page` / `when` + exception policy.

Lineage#

Direct inspiration: Railway Oriented Programming, popularized by Scott Wlaschin (F#).

02.03.04 — chain_actions and ChainRunner

Wed, 20 May 2026 00:00:00 +0000

02.03.04 — `chain_actions` and `ChainRunner`#

Source file: src/ocarina/dsl/testing_with_railway/chain_actions.py

The primitive that makes the DSL “flat.” Without it, an N-step scenario is a staircase of .then(...).failure(...).success(...).execute(). With it, it’s a list.

“Parenthesis hell”#

Solution:
# Flat, readable syntax
runner = chain_actions(
    action1.failure(h1).success(h2),
    action2.failure(h3).success(h4),
    action3.failure(h5).success(h6)
)
chain = runner.run()  # Execute when ready
Benefits:

Lazy evaluation: Build chain without executing

Flat syntax: No deep nesting

Automatic short-circuiting: Stops on first failure

Composability: ChainRunner is a value

(Excerpt from the docstring.)

02.04.04 — .then(...) and chain_validations(...)

Wed, 20 May 2026 00:00:00 +0000

02.04.04 — `.then(...)` and `chain_validations(...)`#

Two distinct mechanisms to compose multiple validations into one.

`.then(new_value)`#

def then[U](self, new_value: U, *, name: str | None = None) -> ValidationStartBlock[U]:
    return ValidationStartBlock(new_value, self._chain, name)

Switches the type from T to U. The checker accepts the change.
Keeps the chain (self._chain). Past assertions stay in it; new ones stack on top.
Swaps the name: the name you pass to .then() is the one used for the next assertions, not the previous block’s.

Canonical use case#

validate(user, name="user")
    .assert_that(is_not_none)
    .then(user.email, name="user.email")
    .assert_that(is_email)
    .then(user.age, name="user.age")
    .assert_that(is_positive)
    .assert_that(is_less_than_or_equal_to(120))
    .execute()
    .raise_if_invalid()

Reads as: validate user, then user.email, then user.age. All pass → OK. One fails → every error rolls up into the AggregateInvariantViolationError.

02.05.04 — TestSuite[Driver] — parallelized engine

Wed, 20 May 2026 00:00:00 +0000

02.05.04 — `TestSuite[Driver]` — parallelized engine#

Source file: src/ocarina/dsl/testing/oc_test_suite.py

One job: run a sequence of Tests in parallel, handle saturation, ID filtering, and pre-execution invariant validation.

Constructor#

def __init__(
    self,
    *,
    name: str,
    tests: Sequence[Test[Driver]],
    create_logger: Thunk[ILogger],
    drivers_pool: WebDriversPool[Driver],
    take_screenshot: ITakeScreenshot[Driver],
    act_counter: ActCounter | None = None,
    transient_errors: tuple[type[Exception], ...] = (),
    copy_indicator: str = "COPY",
    put_space_after_copy_indicator: bool = True,
    max_retries_per_test: int | None = None,
    autoscreen_on_fail: bool = False,
    saturate_workers: bool | None = None,
    only_ids: Iterable[str] = (),
    exclude_ids: Iterable[str] = (),
) -> None:
    self._guards_on_invoke(tests)
    # ... assignments ...
    self._tests = filter_tests_by_ids(
        tests,
        only=only_ids,
        exclude=exclude_ids,
        logger=create_logger().set_prefix(lambda: f"{self.name}: filtering tests..."),
    )

Parameter	Type	Role	Default
`name`	`str`	Suite name (appears in logs & reports)	—
`tests`	`Sequence[Test[Driver]]`	List of tests to run	—
`create_logger`	`Thunk[ILogger]`	Logger factory	—
`drivers_pool`	`WebDriversPool[Driver]`	Shared pool	—
`take_screenshot`	`ITakeScreenshot[Driver]`	Callable `(driver, logger, category) -> None`	—
`act_counter`	`ActCounter \| None`	If `None` → `ThreadsBasedActCounter()`	`None`
`transient_errors`	`tuple[type[Exception], ...]`	Exceptions that trigger a retry	`()`
`copy_indicator`	`str`	Prefix for saturation-cloned tests	`"COPY"`
`put_space_after_copy_indicator`	`bool`	`[COPY 1]` (`True`) vs `[COPY1]` (`False`)	`True`
`max_retries_per_test`	`int \| None`	Max retries for a potentially flaky test	`None` → `_DEFAULT_MAX_RETRIES_PER_TEST` (8)
`autoscreen_on_fail`	`bool`	Automatically capture one or several screenshots (burst) on failure	`False`
`saturate_workers`	`bool \| None`	Clone tests to saturate every worker if the pool is large enough	`None` → cascade: suite > campaign > bootstrap
`only_ids`	`Iterable[str]`	`--only` filter	`()`
`exclude_ids`	`Iterable[str]`	`--exclude` filter	`()`

Guardrails#

At `init` time#

def _guards_on_invoke(self, tests: Sequence[Test[Driver]]) -> None:
    validate_test_runners_ids(tests=tests, name="tests").execute().raise_if_invalid()

→ Every test_id must be unique. Otherwise: AggregateInvariantViolationError. Raised at construction, before any execution attempt. Duplicate a test_id by accident and you find out instantly.

02.10.04 — ActCounter + ThreadsBasedActCounter

Wed, 20 May 2026 00:00:00 +0000

02.10.04 — `ActCounter` + `ThreadsBasedActCounter`#

Thread-local counter of act calls per attempt. Lets the report say “this test made 17 steps before dying at step 18.”

Interface#

# src/ocarina/infra/act_counter.py
class ActCounter:
    def get(self) -> int: ...
    def reset(self) -> None: ...
    def incr_act_call_count(self) -> None: ...

Default implementation#

# src/ocarina/opinionated/infra/act_counter.py
from threading import local

_thread_local = local()
_COUNTER_KEY: Final[str] = "ocarina_counter"


class ActCounter(_ActCounter):
    def get(self) -> int:
        return getattr(_thread_local, _COUNTER_KEY, 0)

    def reset(self) -> None:
        setattr(_thread_local, _COUNTER_KEY, 0)

    def incr_act_call_count(self) -> None:
        if not hasattr(_thread_local, _COUNTER_KEY):
            self.reset()
        setattr(_thread_local, _COUNTER_KEY, getattr(_thread_local, _COUNTER_KEY) + 1)

threading.local(): namespace where attributes are per thread. Each thread has its own value.
_COUNTER_KEY = "ocarina_counter": attribute key.
No lock: each thread only writes its own value, so no race.

Why thread-local rather than a shared counter + lock?#

Ocarina’s architecture says one thread = one test. We’ve got no appetite for a whole state monad — might as well park this “impurity” (still a piece of state) right here. That’s it.

02.11.04 — Loggers: PrintLogger, FileLogger, PrintAndFileLogger, MutedLogger

Wed, 20 May 2026 00:00:00 +0000

02.11.04 — Loggers: `PrintLogger`, `FileLogger`, `PrintAndFileLogger`, `MutedLogger`#

Source folder: src/ocarina/opinionated/loggers/

Four canonical ILogger implementations + a create_matching_logger factory. All opt-in.

`create_matching_logger`#

LOGGERS_CHOICES = ("terminal", "file", "terminal+file", "muted")

def create_matching_logger(mode: SupportedLogger) -> ILogger:
    if mode == "terminal":
        return PrintLogger()
    if mode == "file":
        return FileLogger(base_dir=get_default_log_dir())
    if mode == "terminal+file":
        return PrintAndFileLogger(base_dir=get_default_log_dir())
    if mode == "muted":
        return MutedLogger()
    raise ValueError(f"Unsupported logger mode: {mode}")

And:

def get_default_log_dir() -> Path:
    return Path.cwd() / ".ocarina_logs"

→ By default, logs land in .ocarina_logs/ at the user project root. Gitignored by convention.

`PrintLogger`#

class PrintLogger(ILogger):
    def __init__(self) -> None:
        self._prefix_thunk: Thunk[str] = lambda: ""
        self._domain_taxonomy: tuple[str, ...] = ("",)

    def set_prefix(self, prefix_thunk: Thunk[str]) -> Self:
        self._prefix_thunk = prefix_thunk
        return self

    def set_domain_taxonomy(self, taxonomy: tuple[str, ...]) -> Self:
        self._domain_taxonomy = taxonomy
        return self

    def raw(self, *args, stream=None, **kwargs) -> None:
        if stream is None:
            stream = sys.stdout
        print(*args, file=stream, **kwargs)

    def info(self, msg, *args, exc=None, **kwargs):
        self._print_log("[INFO]", msg, *args, exc=exc, stream=sys.stdout)
    # ... id. for critical / error / warning / debug / success / test_name ...

State: _prefix_thunk (Thunk) + _domain_taxonomy (tuple).
Output: sys.stdout (info, debug, success, test_name) or sys.stderr (critical, error, warning, exception).
Format: typically <prefix> [LEVEL] <message>, with ANSI colors if terminal.
cleanup(): no-op.

`FileLogger`#

@final
class FileLogger(PrintLogger):
    def __init__(
        self, *,
        base_dir: Path,
        with_flush_effect: bool = True,
        with_fallback_on_print_logger_when_no_taxonomy_effect: bool = True,
    ) -> None:
        self._base_dir = base_dir
        self._with_flush_effect = with_flush_effect
        self._with_fallback_on_print_logger_when_no_taxonomy_effect = (
            with_fallback_on_print_logger_when_no_taxonomy_effect
        )
        super().__init__()

    @property
    def _log_file_path(self) -> Path:
        if len(self._domain_taxonomy) == 1:
            folder_path = self._base_dir
            file_name = f"{self._domain_taxonomy[0]}.log"
        else:
            folder_path = self._base_dir.joinpath(*self._domain_taxonomy[:-1])
            file_name = f"{self._domain_taxonomy[-1]}.log"
        folder_path.mkdir(parents=True, exist_ok=True)
        return folder_path / file_name

Taxonomy	Folder	File
`("")`	—	→ Fallback to PrintLogger if enabled
`("annoncements",)`	`base_dir`	`annoncements.log`
`("e2e", "Login")`	`base_dir/e2e`	`Login.log`
`("e2e", "Login", "happy paths", "Login without OTP")`	`base_dir/e2e/Login/happy paths`	`Login without OTP.log`

The taxonomy is the folder tree. The DOCX reports (see 05-plugins-reports.md) walk it recursively and emit one .docx per test case.

Chapter 02.04 — Invariants

Wed, 20 May 2026 00:00:00 +0000

Chapter 02.04 — Invariants#

Ocarina’s sub-DSL for typed, composable invariants. Used everywhere: CLI, POMs, the custom_invariants/testing/ that check suite consistency before any test runs.

Plan#

#	File	Subject
01	`01-validate-flow.md`	The full flow `validate(value) → assert_that → execute → raise_if_invalid` + the `_ValidationChain` class.
02	`02-assertions.md`	Catalog of builtin assertions (`is_str`, `is_email`, `is_positive`, `is_in`, `has_unique_elements`, `each`, `is_valid_filename`, …).
03	`03-otherwise-any-of.md`	`.otherwise(...)` and the OR combination via `_any_of`.
04	`04-then-chain-of-validations.md`	`.then(new_value)` and `chain_validations(...)` for composition.
05	`05-business-vs-framework-validator.md`	`BusinessInvariantValidator` vs `FrameworkInvariantValidator`
06	`06-invariant-errors.md`	`InvariantViolationError`, `DuplicatesError`, `AggregateInvariantViolationError`.

Why the invariants DSL#

Pre-execution guard. TestSuite.__init__ checks — before launching anything — that test names / IDs are unique, max_workers >= 1, etc.
CLI validation. Every flag carries its validate=lambda chain: chain.assert_that(...) inside the CliStore. Errors aggregate into one message.
POM-side validation. POM actions validate their parameters ("retries must be positive") via validate(retries, name="retries").assert_that(is_positive).execute().raise_if_invalid().

The Holy Book sums it up:

02.03.05 — create_act and its hooks

Wed, 20 May 2026 00:00:00 +0000

02.03.05 — `create_act` and its hooks#

Source file: src/ocarina/dsl/testing_with_railway/constructors/create_act.py

The low-level primitive that builds a test step constructor. You call it once to mint a project-specific act verb. In theory a complex project might want several distinct act verbs with different hooks, but no real-world need has shown up yet — recommendation: create one. Not a singleton, just a convention.

Signature#

def create_act(
    pom: TPOM,
    action: Callable[[TPOM], TPOM],
    *,
    on_failure: Callable[[TPOM, Exception], Fail] | None = None,
    on_run_effect: Effect | None = None,
    act_counter_effect: Effect | None = None,
) -> ActionStart[TPOM]:

Parameter	Position	Type	Role
`pom`	positional	`TPOM` (bound `POMBase`)	The page (or any `POMBase` subclass) you’re acting on.
`action`	positional	`Callable[[TPOM], TPOM]`	The function that acts on the page and returns the page (fluent). Identity-typed.
`on_failure`	keyword-only	`Callable[[TPOM, Exception], Fail] \| None`	Hook for refining the `Fail`: if you reach this, you’ve already failed; the hook just lets you type the error more precisely (e.g. `HttpErrorPageReachedError`).
`on_run_effect`	keyword-only	`Effect \| None`	Side effect called before the action (e.g.: log a step number).
`act_counter_effect`	keyword-only	`Effect \| None`	Additional side effect called before the action. Default: increments the act counter.

Code#

def run_action() -> Result[TPOM]:
    try:
        if act_counter_effect:
            act_counter_effect()
        else:
            ThreadsBasedActCounter().incr_act_call_count()

        if on_run_effect:
            on_run_effect()

        result_pom = action(pom)
        return Ok(result_pom)
    except Exception as exc:  # noqa: BLE001
        if on_failure:
            return on_failure(pom, exc)
        return Fail(error=exc)

return ActionStart(run_action)

The try wraps EVERYTHING: act_counter_effect, on_run_effect, and the action. If any side effect raises (say on_run_effect hits a dead resource), it counts as a test-step failure. Everything that runs “during the test step” IS the test step.
Order is deterministic: counter → run effect → action. The counter ticks even if the action ends up failing. Intentional — we want to know how many steps were attempted, not how many passed.
on_failure can return an enriched Fail: that’s where a WebDriverException becomes an HttpErrorPageReachedError.

Default `ActCounter`: `ThreadsBasedActCounter`#

from ocarina.opinionated.infra.act_counter import ActCounter as ThreadsBasedActCounter
# ...
if act_counter_effect:
    act_counter_effect()
else:
    ThreadsBasedActCounter().incr_act_call_count()

Source: src/ocarina/opinionated/infra/act_counter.py

02.04.05 — BusinessInvariantValidator vs FrameworkInvariantValidator

Wed, 20 May 2026 00:00:00 +0000

02.04.05 — `BusinessInvariantValidator` vs `FrameworkInvariantValidator`#

Two factories, identical code, exist purely to signal intent.

Code#

class _BaseCustomInvariantValidator:
    @staticmethod
    def create[T](
        value: T,
        name: str,
        build_chain: Callable[[ValidationStartBlock[T], T], ValidationAssertBlock[T]],
    ) -> ValidationAssertBlock[T]:
        return _create_business_invariant_validator(
            value, name, lambda chain: build_chain(chain, value)
        )


@final
class BusinessInvariantValidator(_BaseCustomInvariantValidator):
    """Factory for creating business domain invariant validators.

    Use this for domain-specific validation logic (e.g., "user must be adult",
    "order total must match items").
    """


@final
class FrameworkInvariantValidator(_BaseCustomInvariantValidator):
    """Factory for creating framework-level invariant validators.

    Use this for technical/framework validation logic (e.g., "config must be valid",
    "test structure must be correct").
    """

def _create_business_invariant_validator[T](
    value: T,
    name: str,
    build_chain: ValidationChainBuilder[T],
) -> ValidationAssertBlock[T]:
    start_block = validate(value, name=name)
    return build_chain(start_block)

Why two classes?#

BusinessInvariantValidator flags a business rule; FrameworkInvariantValidator, a technical framework rule. Intent jumps off the page.
Grep. FrameworkInvariantValidator.create finds every framework invariant in one search. Same for business rules on the project side.
Maintainability. Want to add behavior (different log, different stack trace) to one or the other? Do it without touching every call-site.

Usage#

Invariant	Category	Where it lives
`validate_workers_amount`	Framework	`src/ocarina/custom_invariants/testing/workers.py`
`validate_test_runners_ids`	Framework	`src/ocarina/custom_invariants/testing/oc_test_runners_ids.py`
`validate_test_runners_names`	Framework	`src/ocarina/custom_invariants/testing/oc_test_runners_names.py`
`validate_test_suites_names`	Framework	`src/ocarina/custom_invariants/testing/oc_test_suites_names.py`
`validate_test_campaigns_names`	Framework	`src/ocarina/custom_invariants/testing/oc_test_campaigns_names.py`
`validate_test_cycle_name`	Framework	`src/ocarina/custom_invariants/testing/oc_test_cycles_names.py`
Business example: “the username must be on the whitelist”	Business	To be written on the user project side
Business example: “the booking date must be future and < 1 year”	Business	To be written on the user project side

Full pattern#

# src/ocarina/custom_invariants/testing/workers.py
from ocarina.dsl.invariants.assertions import is_not_zero, is_positive
from ocarina.dsl.invariants.validate import FrameworkInvariantValidator


def _workers_amount_chain(
    chain: ValidationStartBlock[int],
    value: int,
) -> ValidationAssertBlock[int]:
    msg = f"Value Error: Number of workers must be at least 1 (got: {value})."
    return chain.assert_that(is_positive, msg=msg).assert_that(is_not_zero, msg=msg)


def validate_workers_amount(
    *, workers_amount: int, name: str
) -> ValidationAssertBlock[int]:
    """Validate that workers amount is at least 1."""
    return FrameworkInvariantValidator.create(
        workers_amount, name, _workers_amount_chain
    )

Private _workers_amount_chain(chain, value) -> ValidationAssertBlock defines the what.
Public validate_workers_amount(*, workers_amount, name) is the API and delegates to FrameworkInvariantValidator.create.
Caller in TestSuite.run: validate_workers_amount(...).execute().raise_if_invalid().

Which factory for which case#

Holy Book (excerpt from the “Extensibility” chapter):

02.05.05 — Worker saturation

Wed, 20 May 2026 00:00:00 +0000

02.05.05 — Worker saturation#

Ocarina-specific trick: if a suite has fewer tests than workers, tests get randomly cloned until the worker count is filled. Copies are renamed [COPY 1] <name>, [COPY 2] <name>, etc.

Why#

The Holy Book formalizes the rationale in the “First real-world hurdles” chapter:

Its saturate_workers option lets you force random cloning of tests inside a suite.

As soon as there are more available workers in the DriversPool than there are tests to run in a suite, Ocarina will randomly clone tests, start every driver, and assign each one a test to perform.

02.10.05 — Selenium adapters

Wed, 20 May 2026 00:00:00 +0000

02.10.05 — Selenium adapters#

Source folder: src/ocarina/infra/selenium/

Everything that materializes the abstractions (POMBase, WebDriversPool, Screenshotter) in Selenium flavor. Lives outside the pure DSL — and since 1.1.3 it has a twin: src/ocarina/infra/playwright/ ships the exact same contracts in Playwright flavor. Swapping backend is now picking a folder, not writing one.

Files in the folder#

File	Role
`create_driver.py`	`_build_firefox`, `_build_chrome`, `_build_edge`, `_build_safari` + dispatch
`create_drivers_pool.py`	`create_selenium_drivers_pool` (uses `DriverBuilder` + `WebDriversPool`)
`create_screenshotter.py`	`create_selenium_screenshotter` + `_selenium_save_full_page` (Firefox-only)
`driver_healthcheck.py`	`driver_healthcheck(driver)` — pings `driver.title`
`mixins.py`	`SeleniumTitleMixin`

`create_driver.py`#

def _build_firefox(*, profile_path, driver_path, headless, wait_timeout) -> WebDriver:
    service = FirefoxService(executable_path=driver_path)
    options = FirefoxOptions()
    if headless:
        options.add_argument("-headless")
    if profile_path:
        options.profile = FirefoxProfile(profile_path)
    driver = Firefox(service=service, options=options)
    driver.implicitly_wait(wait_timeout)
    return driver


def _build_chrome(*, profile_path, driver_path, headless, wait_timeout) -> WebDriver:
    service = ChromeService(executable_path=driver_path)
    options = ChromeOptions()
    if headless:
        options.add_argument("--headless=new")
    if profile_path:
        options.add_argument(f"--user-data-dir={profile_path}")
    driver = Chrome(service=service, options=options)
    driver.implicitly_wait(wait_timeout)
    return driver


def _build_edge(*, profile_path, driver_path, headless, wait_timeout) -> WebDriver:
    # … same as Chrome with EdgeService/EdgeOptions/Edge …


def _build_safari(*, profile_path, driver_path, headless, wait_timeout) -> WebDriver:
    # … Safari supports neither driver_path (uses macOS' native safaridriver),
    #   nor profile_path (no custom profile), nor headless …

1. `implicitly_wait` set only once#

Each builder calls driver.implicitly_wait(wait_timeout) once. Any find_element that doesn’t find the element immediately waits up to wait_timeout seconds before raising NoSuchElementException.

02.11.05 — Report plugins

Wed, 20 May 2026 00:00:00 +0000

02.11.05 — Report plugins#

Source folder: src/ocarina/opinionated/plugins/reports/

pretty_print_results, results_to_json, generate_docx_proof, timing. All opt-in. Run sequentially or in parallel via run_plugins.

`pretty_print_results`#

# src/ocarina/opinionated/plugins/reports/pretty_print_results.py
def pretty_print_results(results: TestCycleResults, *, with_colors: bool = False) -> None:
    """Display the full test results."""

Campaign
• Suite
  > Test case 1
    » PASSED
  > Test case 2
    » FAILED
      → Error message
        ⫸ At step 3
  > Test case 3
    » SKIPPED

Test results:
1 FAILED | 1 PASSED | 1 SKIPPED

Aspect	Detail
Hierarchy	3 levels: campaign `•`, suite `>`, case `»`
Levels	`PASSED` (green), `FAILED` (red), `SKIPPED` (gray)
Error	Message + step number where it failed ("At step 3")
Summary	Aggregated count at the bottom

`results_to_json`#

def generate_json_results(*, results: TestCycleResults, output_dir: Path, logger: ILogger) -> None:
    """Write test results to a JSON file in results_dir."""
    output_dir.mkdir(parents=True, exist_ok=True)
    max_stem_length = 8
    max_attempts = 500
    for _ in range(max_attempts):
        filename = f"{uuid.uuid4().hex[:max_stem_length]}.json"
        file_path = output_dir / filename
        if not file_path.exists():
            break
    else:
        raise RuntimeError(f"Can't generate unique JSON filename in: {output_dir}.")

{
  "Campaign": {
    "Suite": {
      "test_case": [
        {"status": "success" | "fail", "error": "..."},
        counter,
        metadata
      ]
    }
  }
}

def _result_to_serializable(v: Any) -> dict[str, str]:
    if is_ok(v):
        return {"status": "success"}
    if is_fail(v):
        return {"status": "fail", "error": str(v.error)}
    raise TypeError(f"Expected Ok or Fail instances, but got: {type(v)}")

Filename is an 8-char hex UUID → 16⁸ ≈ 4 billion options. No collisions in practice. 500 safety retries.

Chapter 02.05 — Orchestration

Wed, 20 May 2026 00:00:00 +0000

Chapter 02.05 — Orchestration#

Test → TestSuite → TestCampaign → TestCycle: how each level slots into the next, who owns parallelization, who owns retries, who decides skipping, and where the pre-execution invariants live.

Plan#

#	File	Subject
01	`01-test.md`	The `Test[Driver]` class — `spawn`, pre/post fragments, skip.
02	`02-test-executor.md`	`TestExecutor` — execution of one attempt, order: setup → watchers.start → chain → watchers.stop → teardown.
03	`03-test-flow-retries.md`	`TestFlow` — retry loop (1 + max_retries), linear backoff, setup-failure handling.
04	`04-test-suite.md`	`TestSuite` — parallelization with `ThreadPoolExecutor`, ID filtering, guardrails.
05	`05-saturation.md`	Worker saturation: random cloning `[COPY N]`. Why and how.
06	`06-test-campaign.md`	`TestCampaign` — sequence of suites, `campaign_has_failed`.
07	`07-test-cycle-modes.md`	`TestCycle` — smoke + main, `fail-fast` vs `wait-for-all` modes, `has_test_cycle_failed`.
08	`08-filter-tests-by-ids.md`	`filter_tests_by_ids` — `--only`/`--exclude`, mutex, ignores unknown IDs.

Diagram#

            ┌────────────────────────────────────────────────┐
            │                  TestCycle                     │
            │                                                │
            │  ┌──────────────────────────────────────────┐  │
            │  │ smoke_tests_campaigns                    │  │ ◄── first, gate
            │  │  └─ TestCampaign                         │  │     mode: fail-fast |
            │  │      └─ TestSuite                        │  │           wait-for-all
            │  │          └─ Test                         │  │
            │  └──────────────────────────────────────────┘  │
            │                                                │
            │  ┌──────────────────────────────────────────┐  │
            │  │ campaigns (main)                         │  │ ◄── skipped if a
            │  │  └─ TestCampaign                         │  │     smoke fails
            │  │      └─ TestSuite                        │  │
            │  │          └─ Test                         │  │
            │  └──────────────────────────────────────────┘  │
            └────────────────────────────────────────────────┘

Who does what?#

Level	Single responsibility	Concurrency	Out of scope
`Test`	Metadata + `spawn(driver, logger)`	none	execution
`TestExecutor`	One attempt	none	retries, driver acquisition
`TestFlow`	Retry loop	none	parallelization, aggregation
`TestSuite`	Parallelization + saturation + ID filtering	N threads	inter-suite sequence
`TestCampaign`	Sequence of suites	suite-level	smoke vs main
`TestCycle`	Smoke + main + mode	campaign-level	bootstrap / post-exec plugins

The strict separation is deliberate. TestExecutor knows nothing about retries. TestFlow knows nothing about concurrency. TestSuite knows nothing about campaign-level aggregation. One axis of responsibility per class.

02.10.06 — The Playwright actor: one owner thread

Mon, 01 Jun 2026 00:00:00 +0000

02.10.06 — The Playwright actor: one owner thread#

Source folder: src/ocarina/infra/playwright/

The Playwright adapter mirrors the Selenium one file for file (create_driver, create_drivers_pool, create_screenshotter, driver_healthcheck, mixins), with one extra file: driver.py. That file deserves a chapter of its own. It is what reconciles Playwright’s sync API — inherently bound to one thread — with Ocarina’s threaded model (pool, warmup, Watcher). The model has been stressed and stabilized; it holds.

The problem: Playwright’s sync API is thread-affine#

Playwright’s sync API binds every object it hands out — Playwright, Browser, BrowserContext, Page, Locator, … — to the thread that called sync_playwright().start(). Under the hood it is a greenlet pinned to that thread. Touching any of them from another thread raises:

02.03.06 — drive_page

Wed, 20 May 2026 00:00:00 +0000

02.03.06 — `drive_page`#

Source file: src/ocarina/opinionated/dsl/drive_page.py

Code#

def drive_page(
    first: ActionSuccess[TPOM], *rest: ActionSuccess[TPOM]
) -> ChainRunner[TPOM]:
    return chain_actions(first, *rest)

Literally chain_actions.

Why this alias?#

1. Semantics: “I’m taking control of a page”#

Holy Book quote (“First scenarios”):

drive_page expresses the fact that you are taking control of one page. Any transition becomes explicit through the opening of a new drive_page.

return [
    drive_page(
        act(on_homepage, open_homepage)...,
        act(on_homepage, verify_homepage)...,
        act(on_homepage, click_cta)...,
    ),                                          # ⬅ closing control of the homepage
    drive_page(                                 # ⬅ opening control of the next page
        act(on_target_page, verify_target_page)...,
    ),
]

2. Discipline#

Mixing acts from two different POMs inside one drive_page is a mypy error (see 02-action-chain-states.md, “narrowing via act()” section). The semantics get enforced concretely.

02.04.06 — Invariant error hierarchy

Wed, 20 May 2026 00:00:00 +0000

02.04.06 — Invariant error hierarchy#

Source file: src/ocarina/dsl/invariants/errors.py

InvariantViolationError (base — subclass of Exception)
├── DuplicatesError                  (raised by `has_unique_elements`)
└── AggregateInvariantViolationError (raised by `_ValidationResult.raise_if_invalid`)

`InvariantViolationError`#

class InvariantViolationError(Exception):
    """Base exception raised when an invariant is violated."""

Bare Exception subclass, no extra logic. Every predicate raises this (or a subclass).

try:
    validate(value).assert_that(predicate).execute().raise_if_invalid()
except InvariantViolationError as e:
    logger.error(f"Validation failed: {e}")

… catches every violation with a single clause.

`DuplicatesError`#

class DuplicatesError(InvariantViolationError):
    def __init__(self, duplicates: Sequence[Any], message: str | None = None) -> None:
        self.duplicates = duplicates
        msg = message or "Duplicate elements detected:\n" + "\n".join(
            f" - {d}" for d in duplicates
        )
        super().__init__(msg)

Stashes the duplicate list in .duplicates.
Default message: “Duplicate elements detected:\n - apple\n - banana”.
Accepts a custom message=.

Raised by has_unique_elements.

02.05.06 — TestCampaign[Driver]

Wed, 20 May 2026 00:00:00 +0000

02.05.06 — `TestCampaign[Driver]`#

Source file: src/ocarina/dsl/testing/oc_test_campaign.py

One job: run a sequence of suites in order, share a workers config, and declare campaign_has_failed.

Code#

class TestCampaign[Driver]:
    def __init__(
        self,
        *,
        name: str,
        suites: Sequence[TestSuite[Driver]],
        max_workers: int,
        saturate_workers: bool | None = None,
    ) -> None:
        validate_test_suites_names(suites=suites, name="suites").execute().raise_if_invalid()

        self.name = name
        self._suites = suites
        self._results: TestCampaignResults = {}
        self._max_workers = max_workers
        self._saturate_workers = saturate_workers

        for suite in self._suites:
            suite._campaign_name = self.name

    def run_all(
        self, *, skip_all: bool = False, saturate_workers: bool = True
    ) -> TestCampaignResults:
        self._results.clear()

        resolved_saturate_workers = (
            self._saturate_workers
            if self._saturate_workers is not None
            else saturate_workers
        )

        if skip_all:
            for suite in self._suites:
                self._results[suite.name] = {
                    name: (None, -1, test_id)
                    for name, test_id in suite.test_names_and_ids
                }
            return self._results

        for suite in self._suites:
            self._results[suite.name] = suite.run(
                max_workers=self._max_workers,
                saturate_workers=resolved_saturate_workers,
            )

        return self._results


def campaign_has_failed(results: TestCampaignResults) -> bool:
    return any(
        is_test_result_fail(outcome)
        for campaign_results in results.values()
        for outcome, _, _ in campaign_results.values()
    )

Anatomy#

Constructor guard#

validate_test_suites_names(suites=suites, name="suites").execute().raise_if_invalid()

→ Suite names inside a campaign must be unique — case-insensitively since 1.1.10 (NFC + casefold). Raised at construction.

02.11.06 — bootstrap + run_plugins

Wed, 20 May 2026 00:00:00 +0000

02.11.06 — `bootstrap` + `run_plugins`#

Source file: src/ocarina/opinionated/launcher/bootstrap.py

Entry point of an Ocarina project.
Three steps: cycle.run_all → run_plugins → post_exec.

Code#

def bootstrap[T](
    *,
    test_cycle: TestCycle[T],
    run_plugins: Callable[[TestCycleResults], None],
    post_exec: Callable[[TestCycleResults], None] | None = None,
    saturate_workers: bool = True,
) -> None:
    results = test_cycle.run_all(saturate_workers=saturate_workers)
    run_plugins(results)
    if post_exec:
        post_exec(results)

Order#

1. cycle.run_all()  →  results
2. run_plugins(results)
3. post_exec(results) (optional)

Step	Effect	Why this order
1	All tests run	We need `results` for the rest
2	Plugins fire (DOCX, JSON, etc.)	Must run before `post_exec` since it can take generation time
3	Post-exec (pretty_print + sys.exit)	Last thing — after this, the process is dead

Typing#

run_plugins: Callable[[TestCycleResults], None]
post_exec: Callable[[TestCycleResults], None] | None = None

Both receive the results as an argument:

02.03.07 — match_page / when

Wed, 20 May 2026 00:00:00 +0000

02.03.07 — `match_page` / `when`#

Source file: src/ocarina/dsl/testing_with_railway/match_page.py

Bolted onto the framework after the fact. The Holy Book puts it bluntly: “match_page and when were added after the fact; the Igoristan was so random that the use case forced itself onto us. Their implementation was simple, proof of the grammar’s flexibility: other analogous structures could follow just as easily.”

The problem#

Some pages render differently:

Cookies banner showing or not.
A/B test serving two UI variants.
Degraded mode (maintenance page) instead of the real page.
Anti-bot captcha.
…

The scenario needs to branch without breaking the ROP chain.

02.05.07 — TestCycle[Driver] + modes

Wed, 20 May 2026 00:00:00 +0000

02.05.07 — `TestCycle[Driver]` + modes#

Source file: src/ocarina/dsl/testing/oc_test_cycle.py

One job: orchestrate smoke then main campaigns, and apply a smoke-failure-handling mode.

Two modes#

type Mode = Literal[
    "fail-fast-on-first-smoke-campaigns-sequence-fail",
    "wait-for-all-smoke-tests",
]

Mode	Behavior
`fail-fast-on-first-smoke-campaigns-sequence-fail` (default)	First smoke campaign that fails → following ones get skipped.
`wait-for-all-smoke-tests`	Every smoke campaign runs. If any fails, the main campaigns get skipped.

Case	Mode
Dependency-style smoke (e.g. “login” then “dashboard accessible”)	`fail-fast` (login dies → dashboard pointless)
Parallel smoke (e.g. “homepage” + “API ping”)	`wait-for-all` (we want to see both)

fail-fast is the default — it’s the common case.

02.05.08 — filter_tests_by_ids

Wed, 20 May 2026 00:00:00 +0000

02.05.08 — `filter_tests_by_ids`#

Source file: src/ocarina/dsl/testing/filter_tests_by_ids.py

Called by TestSuite.__init__ to apply the CLI flags --only <ids> and --exclude <ids>. Mutually exclusive — can’t pass both.

Code#

def filter_tests_by_ids[Driver](
    tests: Sequence[Test[Driver]],
    *,
    only: Iterable[str] = (),
    exclude: Iterable[str] = (),
    logger: ILogger,
) -> Sequence[Test[Driver]]:
    only_set = set(only)
    exclude_set = set(exclude)

    if only_set and exclude_set:
        raise ValueError("--only and --exclude cannot be used together")

    known_ids = {test.test_id for test in tests}

    if only_set:
        matched = only_set & known_ids
        if matched:
            joined = ", ".join(sorted(matched))
            logger.info(f"--only: matched test IDs: {joined}")
        return [test for test in tests if test.test_id in only_set]

    if exclude_set:
        matched = exclude_set & known_ids
        if matched:
            joined = ", ".join(sorted(matched))
            logger.info(f"--exclude: matched test IDs: {joined}")
        return [test for test in tests if test.test_id not in exclude_set]

    return tests

Four guarantees#

1. Mutex `--only` / `--exclude`#

if only_set and exclude_set:
    raise ValueError("--only and --exclude cannot be used together")

Passing both is a runtime error (not a mypy one). Semantically nonsense: “keep only A, B” AND “exclude C, D”? At the CLI level, doesn’t make sense. The mutex kills ambiguity.

Chapter 02.10 — Infrastructure

Wed, 20 May 2026 00:00:00 +0000

Chapter 02.10 — Infrastructure#

Everything that touches external resources: driver pool, builders, screenshotters, act counter, and the Selenium adapters that implement them. Since 1.1.3, a parallel infra/playwright/ ships the same contracts in Playwright flavor — same pool, same builder, same ports.

Plan#

#	File	Subject
01	`01-drivers-pool.md`	`WebDriversPool[Driver]`: `Semaphore`, `Queue`, `warmup` with watchdog, `shutdown`.
02	`02-driver-builder.md`	`DriverBuilder[Driver]`: profile and tmp dirs handling.
03	`03-screenshotter.md`	`Screenshotter[TDriver]` + `ScreenshotterConfig`: burst, healthcheck, threadsafe.
04	`04-act-counter.md`	`ActCounter` + `ThreadsBasedActCounter` (thread-local).
05	`05-selenium-adapters.md`	`create_driver` (Firefox/Chrome/Edge/Safari), `create_drivers_pool`, `create_screenshotter`, `driver_healthcheck`, `SeleniumTitleMixin`.
06	`06-playwright-actor.md`	The `PlaywrightDriver` actor: owner thread, marshalling through `submit`, the `call_timeout` liveness ceiling, cross-thread warmup, observe-only Watcher.

`BuiltWebDriver[Driver]`#

type BuiltWebDriver[Driver] = tuple[Driver, Effect]

The exchange unit between the builder and the pool: a (driver, dispose) tuple. dispose is an Effect (no argument, no return) that knows how to clean up that exact driver (driver.quit() + removal of the tmp profile if needed).

Chapter 02.11 — opinionated/ layer

Wed, 20 May 2026 00:00:00 +0000

Chapter 02.11 — `opinionated/` layer#

Everything that’s opt-in: a picky user can swap any of it. CLI, loggers, report plugins, bootstrap, drive_page alias. This layer is what you see on the surface, not the core — the turnkey version Ocarina ships so a typical project doesn’t have to reinvent it.

Plan#

#	File	Subject
01	`01-cli-builder.md`	`CliBuilder`, `CliArg`, `_SilentArgumentParser`.
02	`02-cli-store-phantoms.md`	`CliStore[TKeys]`, `_CliField[T]`, `phantom_validate`.
03	`03-selenium-cli.md`	`create_selenium_auto_cli_store` + flags + validation.
04	`04-loggers.md`	`ILogger` implementations: `PrintLogger`, `FileLogger`, `PrintAndFileLogger`, `MutedLogger`, `create_matching_logger`.
05	`05-plugins-reports.md`	`pretty_print_results`, `results_to_json`, `generate_docx_proof`, `timing`.
06	`06-bootstrap-launcher.md`	`bootstrap` + `run_plugins` (parallel).

Opt-out / opt-in#

Without `opinionated/`	With `opinionated/`
Write your CLI from scratch	`create_selenium_auto_cli_store()` hands it to you
Write your logger	`create_matching_logger("terminal+file")` hands it to you
Write your reports	`pretty_print_results`, `generate_json_results`, `generate_docx_proof`
Write your `main()`	`bootstrap(test_cycle, run_plugins, post_exec)`

Alternatives#

Component	Replaceable by…
`CliBuilder` / `CliStore`	Any argparse-like lib (click, typer, fire)
`PrintLogger` / `FileLogger`	Any `ILogger` implementation
`pretty_print_results`	Any `(TestCycleResults) -> None` function
`generate_docx_proof`	Same
`bootstrap`	Any `() -> None` function that calls `TestCycle.run_all` + post-processes
`drive_page`	`chain_actions` directly, or a project alias (`drive_section`, `drive_widget`)

Ocarina on Ocarina — manual

02.03.01 — The Result[T] type

02.03.01 — The Result[T] type#

Code#

Six design decisions, dissected#

1. _BaseResult as a common parent#

02.04.01 — The validate → assert_that → execute → raise_if_invalid flow

02.04.01 — The validate → assert_that → execute → raise_if_invalid flow#

The state machine#

Diagram#

assert_that loop#

02.05.01 — Test[Driver]

02.05.01 — Test[Driver]#

Signature#

1. @final#

02.10.01 — WebDriversPool[Driver]

02.10.01 — WebDriversPool[Driver]#

Constructor#

acquire()#

1. No reuse#

02.11.01 — CliBuilder + CliArg + _SilentArgumentParser

02.11.01 — CliBuilder + CliArg + _SilentArgumentParser#

_SilentArgumentParser#

02.03.02 — The builder state machine

02.03.02 — The builder state machine#

Overview#

The types Action, FailureHandler, SuccHandler#

Typestate Pattern: why you can’t get it wrong#

02.04.02 — Catalog of builtin assertions

02.04.02 — Catalog of builtin assertions#

Full table#

A few implementations in detail#

is_email#

02.05.02 — TestExecutor[Driver]

02.05.02 — TestExecutor[Driver]#

ExecutionOutcome#

Execution order for one attempt#

execute#

Two loggers: why#

02.10.02 — DriverBuilder[Driver]

02.10.02 — DriverBuilder[Driver]#

Why a builder?#

02.11.02 — CliStore[TKeys] + _CliField[T] + phantom_validate

02.11.02 — CliStore[TKeys] + _CliField[T] + phantom_validate#

_CliField[T] — write-once field#

1. _Unset sentinel#

02.03.03 — The failure rail: NeutralAction*

02.03.03 — The failure rail: NeutralAction*#

Why Neutral classes rather than a user-side if#

02.04.03 — .otherwise(...) and _any_of

02.04.03 — .otherwise(...) and _any_of#

The problem#

Code#

_any_of#

Example#

02.05.03 — TestFlow[Driver] — retry policy

02.05.03 — TestFlow[Driver] — retry policy#

Why an intermediate level between TestSuite and TestExecutor#

02.10.03 — Screenshotter[TDriver]

02.10.03 — Screenshotter[TDriver]#

Protocol#

ScreenshotterConfig[TDriver]#

02.11.03 — Auto CLI store + flags + validation

02.11.03 — Auto CLI store + flags + validation#

Flags#

Literal[...]#

Chapter 02 — Ocarina, the framework

Chapter 02 — Ocarina, the framework#

Chapter plan#

Related reading#

Chapter 02.03 — Railway Oriented Programming

Chapter 02.03 — Railway Oriented Programming#

Plan#

Lineage#

02.03.04 — chain_actions and ChainRunner

02.03.04 — chain_actions and ChainRunner#

“Parenthesis hell”#

02.04.04 — .then(...) and chain_validations(...)

02.04.04 — .then(...) and chain_validations(...)#

.then(new_value)#

02.03.01 — The `Result[T]` type#

1. `_BaseResult` as a common parent#

02.04.01 — The `validate → assert_that → execute → raise_if_invalid` flow#

`assert_that` loop#

02.05.01 — `Test[Driver]`#

1. `@final`#

02.10.01 — `WebDriversPool[Driver]`#

`acquire()`#

02.11.01 — `CliBuilder` + `CliArg` + `_SilentArgumentParser`#

`_SilentArgumentParser`#

The types `Action`, `FailureHandler`, `SuccHandler`#

`is_email`#

02.05.02 — `TestExecutor[Driver]`#

`ExecutionOutcome`#

`execute`#

02.10.02 — `DriverBuilder[Driver]`#

02.11.02 — `CliStore[TKeys]` + `_CliField[T]` + `phantom_validate`#

`_CliField[T]` — write-once field#

1. `_Unset` sentinel#

02.03.03 — The failure rail: `NeutralAction*`#

Why Neutral classes rather than a user-side `if`#

02.04.03 — `.otherwise(...)` and `_any_of`#

`_any_of`#

02.05.03 — `TestFlow[Driver]` — retry policy#

Why an intermediate level between `TestSuite` and `TestExecutor`#

02.10.03 — `Screenshotter[TDriver]`#

`Protocol`#

`ScreenshotterConfig[TDriver]`#

`Literal[...]`#

02.03.04 — `chain_actions` and `ChainRunner`#

02.04.04 — `.then(...)` and `chain_validations(...)`#

`.then(new_value)`#

02.05.04 — `TestSuite[Driver]` — parallelized engine#

At `init` time#

02.10.04 — `ActCounter` + `ThreadsBasedActCounter`#

02.11.04 — Loggers: `PrintLogger`, `FileLogger`, `PrintAndFileLogger`, `MutedLogger`#

`create_matching_logger`#

`PrintLogger`#

`FileLogger`#

02.03.05 — `create_act` and its hooks#

Default `ActCounter`: `ThreadsBasedActCounter`#

02.04.05 — `BusinessInvariantValidator` vs `FrameworkInvariantValidator`#

`create_driver.py`#

1. `implicitly_wait` set only once#

`pretty_print_results`#

`results_to_json`#

02.03.06 — `drive_page`#

`InvariantViolationError`#

`DuplicatesError`#

02.05.06 — `TestCampaign[Driver]`#

02.11.06 — `bootstrap` + `run_plugins`#