"""
Tests for L{eliot._action}.
"""

import pickle
import time
from unittest import TestCase
from unittest.mock import patch
from threading import Thread

from hypothesis import assume, given, settings, HealthCheck
from hypothesis.strategies import integers, lists, just, text

from pyrsistent import pvector, v

import testtools
from testtools.matchers import MatchesStructure

from .._action import (
    Action,
    current_action,
    startTask,
    start_action,
    ACTION_STATUS_FIELD,
    ACTION_TYPE_FIELD,
    FAILED_STATUS,
    STARTED_STATUS,
    SUCCEEDED_STATUS,
    DuplicateChild,
    InvalidStartMessage,
    InvalidStatus,
    TaskLevel,
    WrittenAction,
    WrongActionType,
    WrongTask,
    WrongTaskLevel,
    TooManyCalls,
    log_call,
)
from .._message import (
    EXCEPTION_FIELD,
    REASON_FIELD,
    TASK_LEVEL_FIELD,
    TASK_UUID_FIELD,
    MESSAGE_TYPE_FIELD,
    Message,
)
from .._output import MemoryLogger
from .._validation import ActionType, Field, _ActionSerializers
from ..testing import assertContainsFields, capture_logging
from ..parse import Parser
from .. import (
    add_destination,
    remove_destination,
    register_exception_extractor,
    preserve_context,
)

from .strategies import (
    message_dicts,
    start_action_message_dicts,
    start_action_messages,
    task_level_indexes,
    task_level_lists,
    written_actions,
    written_messages,
    reparent_action,
    sibling_task_level,
    union,
    written_from_pmap,
)


class ActionTests(TestCase):
    """
    Tests for L{Action}.
    """

    def test_start(self):
        """
        L{Action._start} logs an C{action_status="started"} message.
        """
        logger = MemoryLogger()
        action = Action(logger, "unique", TaskLevel(level=[]), "sys:thename")
        action._start({"key": "value"})
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": "unique",
                "task_level": [1],
                "action_type": "sys:thename",
                "action_status": "started",
                "key": "value",
            },
        )

    def test_task_uuid(self):
        """
        L{Action.task_uuid} return the task's UUID.
        """
        logger = MemoryLogger()
        action = Action(logger, "unique", TaskLevel(level=[]), "sys:thename")
        self.assertEqual(action.task_uuid, "unique")

    def test_startMessageSerialization(self):
        """
        The start message logged by L{Action._start} is created with the
        appropriate start message L{eliot._validation._MessageSerializer}.
        """
        serializers = ActionType(
            "sys:thename", [Field("key", lambda x: x, "")], [], ""
        )._serializers

        class Logger(list):
            def write(self, msg, serializer):
                self.append(serializer)

        logger = Logger()
        action = Action(
            logger, "unique", TaskLevel(level=[]), "sys:thename", serializers
        )
        action._start({"key": "value"})
        self.assertIs(logger[0], serializers.start)

    def test_child(self):
        """
        L{Action.child} returns a new L{Action} with the given logger, system
        and name, and a task_uuid taken from the parent L{Action}.
        """
        logger = MemoryLogger()
        action = Action(logger, "unique", TaskLevel(level=[]), "sys:thename")
        logger2 = MemoryLogger()
        child = action.child(logger2, "newsystem:newname")
        self.assertEqual(
            [child._logger, child._identification, child._task_level],
            [
                logger2,
                {"task_uuid": "unique", "action_type": "newsystem:newname"},
                TaskLevel(level=[1]),
            ],
        )

    def test_childLevel(self):
        """
        Each call to L{Action.child} increments the new sub-level set on the
        child.
        """
        logger = MemoryLogger()
        action = Action(logger, "unique", TaskLevel(level=[]), "sys:thename")
        child1 = action.child(logger, "newsystem:newname")
        child2 = action.child(logger, "newsystem:newname")
        child1_1 = child1.child(logger, "newsystem:other")
        self.assertEqual(child1._task_level, TaskLevel(level=[1]))
        self.assertEqual(child2._task_level, TaskLevel(level=[2]))
        self.assertEqual(child1_1._task_level, TaskLevel(level=[1, 1]))

    def test_childSerializers(self):
        """
        L{Action.child} returns a new L{Action} with the serializers passed to
        it, rather than the parent's.
        """
        logger = MemoryLogger()
        serializers = object()
        action = Action(
            logger, "unique", TaskLevel(level=[]), "sys:thename", serializers
        )
        childSerializers = object()
        child = action.child(logger, "newsystem:newname", childSerializers)
        self.assertIs(child._serializers, childSerializers)

    def test_run(self):
        """
        L{Action.run} runs the given function with given arguments, returning
        its result.
        """
        action = Action(None, "", TaskLevel(level=[]), "")

        def f(*args, **kwargs):
            return args, kwargs

        result = action.run(f, 1, 2, x=3)
        self.assertEqual(result, ((1, 2), {"x": 3}))

    def test_runContext(self):
        """
        L{Action.run} runs the given function with the action set as the
        current action.
        """
        result = []
        action = Action(None, "", TaskLevel(level=[]), "")
        action.run(lambda: result.append(current_action()))
        self.assertEqual(result, [action])

    def test_per_thread_context(self):
        """Different threads have different contexts."""
        in_thread = []

        def run_in_thread():
            action = Action(None, "", TaskLevel(level=[]), "")
            with action.context():
                time.sleep(0.5)
                in_thread.append(current_action())

        thread = Thread(target=run_in_thread)
        thread.start()
        time.sleep(0.2)
        self.assertEqual(current_action(), None)
        thread.join()
        self.assertIsInstance(in_thread[0], Action)

    def test_runContextUnsetOnReturn(self):
        """
        L{Action.run} unsets the action once the given function returns.
        """
        action = Action(None, "", TaskLevel(level=[]), "")
        action.run(lambda: None)
        self.assertIs(current_action(), None)

    def test_runContextUnsetOnRaise(self):
        """
        L{Action.run} unsets the action once the given function raises an
        exception.
        """
        action = Action(None, "", TaskLevel(level=[]), "")
        self.assertRaises(ZeroDivisionError, action.run, lambda: 1 / 0)
        self.assertIs(current_action(), None)

    def test_withSetsContext(self):
        """
        L{Action.__enter__} sets the action as the current action.
        """
        action = Action(MemoryLogger(), "", TaskLevel(level=[]), "")
        with action:
            self.assertIs(current_action(), action)

    def test_withUnsetOnReturn(self):
        """
        L{Action.__exit__} unsets the action on successful block finish.
        """
        action = Action(MemoryLogger(), "", TaskLevel(level=[]), "")
        with action:
            pass
        self.assertIs(current_action(), None)

    def test_withUnsetOnRaise(self):
        """
        L{Action.__exit__} unsets the action if the block raises an exception.
        """
        action = Action(MemoryLogger(), "", TaskLevel(level=[]), "")
        try:
            with action:
                1 / 0
        except ZeroDivisionError:
            pass
        else:
            self.fail("no exception")
        self.assertIs(current_action(), None)

    def test_withContextSetsContext(self):
        """
        L{Action.context().__enter__} sets the action as the current action.
        """
        action = Action(MemoryLogger(), "", TaskLevel(level=[]), "")
        with action.context():
            self.assertIs(current_action(), action)

    def test_withContextReturnsaction(self):
        """
        L{Action.context().__enter__} returns the action.
        """
        action = Action(MemoryLogger(), "", TaskLevel(level=[]), "")
        with action.context() as action2:
            self.assertIs(action, action2)

    def test_withContextUnsetOnReturn(self):
        """
        L{Action.context().__exit__} unsets the action on successful block
        finish.
        """
        action = Action(MemoryLogger(), "", TaskLevel(level=[]), "")
        with action.context():
            pass
        self.assertIs(current_action(), None)

    def test_withContextNoLogging(self):
        """
        L{Action.context().__exit__} does not log any messages.
        """
        logger = MemoryLogger()
        action = Action(logger, "", TaskLevel(level=[]), "")
        with action.context():
            pass
        self.assertFalse(logger.messages)

    def test_withContextUnsetOnRaise(self):
        """
        L{Action.conext().__exit__} unsets the action if the block raises an
        exception.
        """
        action = Action(MemoryLogger(), "", TaskLevel(level=[]), "")
        try:
            with action.context():
                1 / 0
        except ZeroDivisionError:
            pass
        else:
            self.fail("no exception")
        self.assertIs(current_action(), None)

    def test_finish(self):
        """
        L{Action.finish} with no exception logs an C{action_status="succeeded"}
        message.
        """
        logger = MemoryLogger()
        action = Action(logger, "unique", TaskLevel(level=[]), "sys:thename")
        action.finish()
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": "unique",
                "task_level": [1],
                "action_type": "sys:thename",
                "action_status": "succeeded",
            },
        )

    def test_successfulFinishSerializer(self):
        """
        L{Action.finish} with no exception passes the success
        L{eliot._validation._MessageSerializer} to the message it creates.
        """
        serializers = ActionType(
            "sys:thename", [], [Field("key", lambda x: x, "")], ""
        )._serializers

        class Logger(list):
            def write(self, msg, serializer):
                self.append(serializer)

        logger = Logger()
        action = Action(
            logger, "unique", TaskLevel(level=[]), "sys:thename", serializers
        )
        action.finish()
        self.assertIs(logger[0], serializers.success)

    def test_failureFinishSerializer(self):
        """
        L{Action.finish} with an exception passes the failure
        L{eliot._validation._MessageSerializer} to the message it creates.
        """
        serializers = ActionType(
            "sys:thename", [], [Field("key", lambda x: x, "")], ""
        )._serializers

        class Logger(list):
            def write(self, msg, serializer):
                self.append(serializer)

        logger = Logger()
        action = Action(
            logger, "unique", TaskLevel(level=[]), "sys:thename", serializers
        )
        action.finish(Exception())
        self.assertIs(logger[0], serializers.failure)

    def test_startFieldsNotInFinish(self):
        """
        L{Action.finish} logs a message without the fields from
        L{Action._start}.
        """
        logger = MemoryLogger()
        action = Action(logger, "unique", TaskLevel(level=[]), "sys:thename")
        action._start({"key": "value"})
        action.finish()
        self.assertNotIn("key", logger.messages[1])

    def test_finishWithBadException(self):
        """
        L{Action.finish} still logs a message if the given exception raises
        another exception when called with C{str()}.
        """
        logger = MemoryLogger()
        action = Action(logger, "unique", TaskLevel(level=[]), "sys:thename")

        class BadException(Exception):
            def __str__(self):
                raise TypeError()

        action.finish(BadException())
        self.assertEqual(
            logger.messages[0]["reason"], "eliot: unknown, str() raised exception"
        )

    def test_withLogsSuccessfulFinishMessage(self):
        """
        L{Action.__exit__} logs an action finish message on a successful block
        finish.
        """
        logger = MemoryLogger()
        action = Action(logger, "uuid", TaskLevel(level=[1]), "sys:me")
        with action:
            pass
        # Start message is only created if we use the action()/task() utility
        # functions, the intended public APIs.
        self.assertEqual(len(logger.messages), 1)
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": "uuid",
                "task_level": [1, 1],
                "action_type": "sys:me",
                "action_status": "succeeded",
            },
        )

    def test_withLogsExceptionMessage(self):
        """
        L{Action.__exit__} logs an action finish message on an exception
        raised from the block.
        """
        logger = MemoryLogger()
        action = Action(logger, "uuid", TaskLevel(level=[1]), "sys:me")
        exception = RuntimeError("because")

        try:
            with action:
                raise exception
        except RuntimeError:
            pass
        else:
            self.fail("no exception")

        self.assertEqual(len(logger.messages), 1)
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": "uuid",
                "task_level": [1, 1],
                "action_type": "sys:me",
                "action_status": "failed",
                "reason": "because",
                "exception": "%s.RuntimeError" % (RuntimeError.__module__,),
            },
        )

    def test_withReturnValue(self):
        """
        L{Action.__enter__} returns the action itself.
        """
        logger = MemoryLogger()
        action = Action(logger, "uuid", TaskLevel(level=[1]), "sys:me")
        with action as act:
            self.assertIs(action, act)

    def test_addSuccessFields(self):
        """
        On a successful finish, L{Action.__exit__} adds fields from
        L{Action.addSuccessFields} to the result message.
        """
        logger = MemoryLogger()
        action = Action(logger, "uuid", TaskLevel(level=[1]), "sys:me")
        with action as act:
            act.addSuccessFields(x=1, y=2)
            act.addSuccessFields(z=3)
        assertContainsFields(self, logger.messages[0], {"x": 1, "y": 2, "z": 3})

    def test_nextTaskLevel(self):
        """
        Each call to L{Action._nextTaskLevel()} increments a counter.
        """
        action = Action(MemoryLogger(), "uuid", TaskLevel(level=[1]), "sys:me")
        self.assertEqual(
            [action._nextTaskLevel() for i in range(5)],
            [
                TaskLevel(level=level)
                for level in ([1, 1], [1, 2], [1, 3], [1, 4], [1, 5])
            ],
        )

    def test_multipleFinishCalls(self):
        """
        If L{Action.finish} is called, subsequent calls to L{Action.finish}
        have no effect.
        """
        logger = MemoryLogger()
        action = Action(logger, "uuid", TaskLevel(level=[1]), "sys:me")
        with action as act:
            act.finish()
            act.finish(Exception())
            act.finish()
        # Only initial finish message is logged:
        self.assertEqual(len(logger.messages), 1)


class StartActionAndTaskTests(TestCase):
    """
    Tests for L{start_action} and L{startTask}.
    """

    def test_startTaskNewAction(self):
        """
        L{startTask} creates a new top-level L{Action}.
        """
        logger = MemoryLogger()
        action = startTask(logger, "sys:do")
        self.assertIsInstance(action, Action)
        self.assertEqual(action._task_level, TaskLevel(level=[]))

    def test_start_task_default_action_type(self):
        """
        L{start_task} sets a default C{action_type} if none is set.
        """
        logger = MemoryLogger()
        startTask(logger)
        assertContainsFields(self, logger.messages[0], {"action_type": ""})

    def test_startTaskSerializers(self):
        """
        If serializers are passed to L{startTask} they are attached to the
        resulting L{Action}.
        """
        logger = MemoryLogger()
        serializers = _ActionSerializers(start=None, success=None, failure=None)
        action = startTask(logger, "sys:do", serializers)
        self.assertIs(action._serializers, serializers)

    def test_startActionSerializers(self):
        """
        If serializers are passed to L{start_action} they are attached to the
        resulting L{Action}.
        """
        logger = MemoryLogger()
        serializers = _ActionSerializers(start=None, success=None, failure=None)
        action = start_action(logger, "sys:do", serializers)
        self.assertIs(action._serializers, serializers)

    def test_startTaskNewUUID(self):
        """
        L{startTask} creates an L{Action} with its own C{task_uuid}.
        """
        logger = MemoryLogger()
        action = startTask(logger, "sys:do")
        action2 = startTask(logger, "sys:do")
        self.assertNotEqual(
            action._identification["task_uuid"], action2._identification["task_uuid"]
        )

    def test_startTaskLogsStart(self):
        """
        L{startTask} logs a start message for the newly created L{Action}.
        """
        logger = MemoryLogger()
        action = startTask(logger, "sys:do", key="value")
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": action._identification["task_uuid"],
                "task_level": [1],
                "action_type": "sys:do",
                "action_status": "started",
                "key": "value",
            },
        )

    def test_start_action_default_action_type(self):
        """
        L{start_action} sets a default C{action_type} if none is set.
        """
        logger = MemoryLogger()
        start_action(logger)
        assertContainsFields(self, logger.messages[0], {"action_type": ""})

    def test_startActionNoParent(self):
        """
        L{start_action} when C{current_action()} is C{None} creates a top-level
        L{Action}.
        """
        logger = MemoryLogger()
        action = start_action(logger, "sys:do")
        self.assertIsInstance(action, Action)
        self.assertEqual(action._task_level, TaskLevel(level=[]))

    def test_startActionNoParentLogStart(self):
        """
        L{start_action} when C{current_action()} is C{None} logs a start
        message.
        """
        logger = MemoryLogger()
        action = start_action(logger, "sys:do", key="value")
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": action._identification["task_uuid"],
                "task_level": [1],
                "action_type": "sys:do",
                "action_status": "started",
                "key": "value",
            },
        )

    def test_startActionWithParent(self):
        """
        L{start_action} uses the C{current_action()} as parent for a new
        L{Action}.
        """
        logger = MemoryLogger()
        parent = Action(logger, "uuid", TaskLevel(level=[2]), "other:thing")
        with parent:
            action = start_action(logger, "sys:do")
            self.assertIsInstance(action, Action)
            self.assertEqual(action._identification["task_uuid"], "uuid")
            self.assertEqual(action._task_level, TaskLevel(level=[2, 1]))

    def test_startActionWithParentLogStart(self):
        """
        L{start_action} when C{current_action()} is an L{Action} logs a start
        message.
        """
        logger = MemoryLogger()
        parent = Action(logger, "uuid", TaskLevel(level=[]), "other:thing")
        with parent:
            start_action(logger, "sys:do", key="value")
            assertContainsFields(
                self,
                logger.messages[0],
                {
                    "task_uuid": "uuid",
                    "task_level": [1, 1],
                    "action_type": "sys:do",
                    "action_status": "started",
                    "key": "value",
                },
            )

    def test_startTaskNoLogger(self):
        """
        When no logger is given L{startTask} logs to the default ``Logger``.
        """
        messages = []
        add_destination(messages.append)
        self.addCleanup(remove_destination, messages.append)
        action = startTask(action_type="sys:do", key="value")
        assertContainsFields(
            self,
            messages[0],
            {
                "task_uuid": action._identification["task_uuid"],
                "task_level": [1],
                "action_type": "sys:do",
                "action_status": "started",
                "key": "value",
            },
        )

    def test_startActionNoLogger(self):
        """
        When no logger is given L{start_action} logs to the default ``Logger``.
        """
        messages = []
        add_destination(messages.append)
        self.addCleanup(remove_destination, messages.append)
        action = start_action(action_type="sys:do", key="value")
        assertContainsFields(
            self,
            messages[0],
            {
                "task_uuid": action._identification["task_uuid"],
                "task_level": [1],
                "action_type": "sys:do",
                "action_status": "started",
                "key": "value",
            },
        )


class PEP8Tests(TestCase):
    """
    Tests for PEP 8 method compatibility.
    """

    def test_add_success_fields(self):
        """
        L{Action.addSuccessFields} is the same as L{Action.add_success_fields}.
        """
        self.assertEqual(Action.addSuccessFields, Action.add_success_fields)

    def test_serialize_task_id(self):
        """
        L{Action.serialize_task_id} is the same as L{Action.serializeTaskId}.
        """
        self.assertEqual(Action.serialize_task_id, Action.serializeTaskId)

    def test_continue_task(self):
        """
        L{Action.continue_task} is the same as L{Action.continueTask}.
        """
        self.assertEqual(Action.continue_task, Action.continueTask)


class SerializationTests(TestCase):
    """
    Tests for L{Action} serialization and deserialization.
    """

    def test_serializeTaskId(self):
        """
        L{Action.serialize_task_id} result is composed of the task UUID and an
        incremented task level.
        """
        action = Action(None, "uniq123", TaskLevel(level=[1, 2]), "mytype")
        self.assertEqual(
            [
                action._nextTaskLevel(),
                action.serialize_task_id(),
                action._nextTaskLevel(),
            ],
            [TaskLevel(level=[1, 2, 1]), b"uniq123@/1/2/2", TaskLevel(level=[1, 2, 3])],
        )

    def test_continueTaskReturnsAction(self):
        """
        L{Action.continue_task} returns an L{Action} whose C{task_level} and
        C{task_uuid} are derived from those in the given serialized task
        identifier.
        """
        originalAction = Action(None, "uniq456", TaskLevel(level=[3, 4]), "mytype")
        taskId = originalAction.serializeTaskId()

        newAction = Action.continue_task(MemoryLogger(), taskId)
        self.assertEqual(
            [newAction.__class__, newAction._identification, newAction._task_level],
            [
                Action,
                {"task_uuid": "uniq456", "action_type": "eliot:remote_task"},
                TaskLevel(level=[3, 4, 1]),
            ],
        )

    def test_continueTaskUnicode(self):
        """
        L{Action.continue_task} can take a Unicode task identifier.
        """
        original_action = Action(None, "uniq790", TaskLevel(level=[3, 4]), "mytype")
        task_id = str(original_action.serialize_task_id(), "utf-8")

        new_action = Action.continue_task(MemoryLogger(), task_id)
        self.assertEqual(new_action._identification["task_uuid"], "uniq790")

    def test_continueTaskStartsAction(self):
        """
        L{Action.continue_task} starts the L{Action} it creates.
        """
        originalAction = Action(None, "uniq456", TaskLevel(level=[3, 4]), "mytype")
        taskId = originalAction.serializeTaskId()
        logger = MemoryLogger()

        Action.continue_task(logger, taskId)
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": "uniq456",
                "task_level": [3, 4, 1, 1],
                "action_type": "eliot:remote_task",
                "action_status": "started",
            },
        )

    def test_continueTaskCustomType(self):
        """
        L{Action.continue_task} uses the provided action type and extra fields.
        """
        originalAction = Action(None, "uniq456", TaskLevel(level=[3, 4]), "mytype")
        taskId = originalAction.serializeTaskId()
        logger = MemoryLogger()

        Action.continue_task(logger, taskId, action_type="custom:action", field="value")
        assertContainsFields(
            self,
            logger.messages[0],
            {
                "task_uuid": "uniq456",
                "task_level": [3, 4, 1, 1],
                "action_type": "custom:action",
                "action_status": "started",
                "field": "value",
            },
        )

    def test_continueTaskNoLogger(self):
        """
        L{Action.continue_task} can be called without a logger.
        """
        originalAction = Action(None, "uniq456", TaskLevel(level=[3, 4]), "mytype")
        taskId = originalAction.serializeTaskId()

        messages = []
        add_destination(messages.append)
        self.addCleanup(remove_destination, messages.append)
        Action.continue_task(task_id=taskId)
        assertContainsFields(
            self,
            messages[-1],
            {
                "task_uuid": "uniq456",
                "task_level": [3, 4, 1, 1],
                "action_type": "eliot:remote_task",
                "action_status": "started",
            },
        )

    def test_continueTaskRequiredTaskId(self):
        """
        L{Action.continue_task} requires a C{task_id} to be passed in.
        """
        self.assertRaises(RuntimeError, Action.continue_task)


class TaskLevelTests(TestCase):
    """
    Tests for L{TaskLevel}.
    """

    def assert_fully_less_than(self, x, y):
        """
        Assert that x < y according to all the comparison operators.
        """
        self.assertTrue(
            all(
                [
                    # lt
                    x < y,
                    not y < x,
                    # le
                    x <= y,
                    not y <= x,
                    # gt
                    y > x,
                    not x > y,
                    # ge
                    y >= x,
                    not x >= y,
                    # eq
                    not x == y,
                    not y == x,
                    # ne
                    x != y,
                    y != x,
                ]
            )
        )

    def test_equality(self):
        """
        L{TaskChild} correctly implements equality and hashing.
        """
        a = TaskLevel(level=[1, 2])
        a2 = TaskLevel(level=[1, 2])
        b = TaskLevel(level=[2, 999])
        self.assertTrue(
            all(
                [
                    a == a2,
                    a2 == a,
                    a != b,
                    b != a,
                    not b == a,
                    not a == b,
                    not a == 1,
                    a != 1,
                    hash(a) == hash(a2),
                    hash(b) != hash(a),
                ]
            )
        )

    def test_as_list(self):
        """
        L{TaskChild.as_list} returns the level.
        """
        self.assertEqual(TaskLevel(level=[1, 2, 3]).as_list(), [1, 2, 3])

    @given(lists(task_level_indexes))
    def test_parent_of_child(self, base_task_level):
        """
        L{TaskLevel.child} returns the first child of the task.
        """
        base_task = TaskLevel(level=base_task_level)
        child_task = base_task.child()
        self.assertEqual(base_task, child_task.parent())

    @given(task_level_lists)
    def test_child_greater_than_parent(self, task_level):
        """
        L{TaskLevel.child} returns a child that is greater than its parent.
        """
        task = TaskLevel(level=task_level)
        self.assert_fully_less_than(task, task.child())

    @given(task_level_lists)
    def test_next_sibling_greater(self, task_level):
        """
        L{TaskLevel.next_sibling} returns a greater task level.
        """
        task = TaskLevel(level=task_level)
        self.assert_fully_less_than(task, task.next_sibling())

    @given(task_level_lists)
    def test_next_sibling(self, task_level):
        """
        L{TaskLevel.next_sibling} returns the next sibling of a task.
        """
        task = TaskLevel(level=task_level)
        sibling = task.next_sibling()
        self.assertEqual(
            sibling, TaskLevel(level=task_level[:-1] + [task_level[-1] + 1])
        )

    def test_parent_of_root(self):
        """
        L{TaskLevel.parent} of the root task level is C{None}.
        """
        self.assertIs(TaskLevel(level=[]).parent(), None)

    def test_toString(self):
        """
        L{TaskLevel.toString} serializes the object to a Unicode string.
        """
        root = TaskLevel(level=[])
        child2_1 = root.child().next_sibling().child()
        self.assertEqual([root.toString(), child2_1.toString()], ["/", "/2/1"])

    def test_fromString(self):
        """
        L{TaskLevel.fromString} deserializes the output of
        L{TaskLevel.toString}.
        """
        self.assertEqual(
            [TaskLevel.fromString("/"), TaskLevel.fromString("/2/1")],
            [TaskLevel(level=[]), TaskLevel(level=[2, 1])],
        )

    def test_from_string(self):
        """
        L{TaskLevel.from_string} is the same as as L{TaskLevel.fromString}.
        """
        self.assertEqual(TaskLevel.from_string, TaskLevel.fromString)

    def test_to_string(self):
        """
        L{TaskLevel.to_string} is the same as as L{TaskLevel.toString}.
        """
        self.assertEqual(TaskLevel.to_string, TaskLevel.toString)


class WrittenActionTests(testtools.TestCase):
    """
    Tests for L{WrittenAction}.
    """

    @given(start_action_messages)
    def test_from_single_start_message(self, message):
        """
        A L{WrittenAction} can be constructed from a single "start" message.
        Such an action inherits the C{action_type} of the start message, has no
        C{end_time}, and has a C{status} of C{STARTED_STATUS}.
        """
        action = WrittenAction.from_messages(message)
        self.assertThat(
            action,
            MatchesStructure.byEquality(
                status=STARTED_STATUS,
                action_type=message.contents[ACTION_TYPE_FIELD],
                task_uuid=message.task_uuid,
                task_level=message.task_level.parent(),
                start_time=message.timestamp,
                children=pvector([]),
                end_time=None,
                reason=None,
                exception=None,
            ),
        )

    @given(start_action_messages, message_dicts, integers(min_value=2))
    def test_from_single_end_message(self, start_message, end_message_dict, n):
        """
        A L{WrittenAction} can be constructed from a single "end"
        message. Such an action inherits the C{action_type} and
        C{task_level} of the end message, has no C{start_time}, and has a
        C{status} matching that of the end message.
        """
        end_message = written_from_pmap(
            union(
                end_message_dict,
                {
                    ACTION_STATUS_FIELD: SUCCEEDED_STATUS,
                    ACTION_TYPE_FIELD: start_message.contents[ACTION_TYPE_FIELD],
                    TASK_UUID_FIELD: start_message.task_uuid,
                    TASK_LEVEL_FIELD: sibling_task_level(start_message, n),
                },
            )
        )
        action = WrittenAction.from_messages(end_message=end_message)
        self.assertThat(
            action,
            MatchesStructure.byEquality(
                status=SUCCEEDED_STATUS,
                action_type=end_message.contents[ACTION_TYPE_FIELD],
                task_uuid=end_message.task_uuid,
                task_level=end_message.task_level.parent(),
                start_time=None,
                children=pvector([]),
                end_time=end_message.timestamp,
                reason=None,
                exception=None,
            ),
        )

    @given(message_dicts)
    def test_from_single_child_message(self, message_dict):
        """
        A L{WrittenAction} can be constructed from a single child
        message. Such an action inherits the C{task_level} of the message,
        has no C{start_time}, C{status}, C{task_type} or C{end_time}.
        """
        message = written_from_pmap(message_dict)
        action = WrittenAction.from_messages(children=[message])
        self.assertThat(
            action,
            MatchesStructure.byEquality(
                status=None,
                action_type=None,
                task_uuid=message.task_uuid,
                task_level=message.task_level.parent(),
                start_time=None,
                children=pvector([message]),
                end_time=None,
                reason=None,
                exception=None,
            ),
        )

    @given(start_action_messages, message_dicts, integers(min_value=2))
    def test_different_task_uuid(self, start_message, end_message_dict, n):
        """
        By definition, an action is either a top-level task or takes place
        within such a task. If we try to assemble actions from messages with
        differing task UUIDs, we raise an error.
        """
        assume(start_message.task_uuid != end_message_dict["task_uuid"])
        action_type = start_message.as_dict()[ACTION_TYPE_FIELD]
        end_message = written_from_pmap(
            union(
                end_message_dict.set(ACTION_TYPE_FIELD, action_type),
                {
                    ACTION_STATUS_FIELD: SUCCEEDED_STATUS,
                    TASK_LEVEL_FIELD: sibling_task_level(start_message, n),
                },
            )
        )
        self.assertRaises(
            WrongTask,
            WrittenAction.from_messages,
            start_message,
            end_message=end_message,
        )

    @given(message_dicts)
    def test_invalid_start_message_missing_status(self, message_dict):
        """
        A start message must have an C{ACTION_STATUS_FIELD} with the value
        C{STARTED_STATUS}, otherwise it's not a start message. If we receive
        such a message, raise an error.

        This test handles the case where the status field is not present.
        """
        assume(ACTION_STATUS_FIELD not in message_dict)
        message = written_from_pmap(message_dict)
        self.assertRaises(InvalidStartMessage, WrittenAction.from_messages, message)

    @given(
        message_dict=start_action_message_dicts,
        status=(just(FAILED_STATUS) | just(SUCCEEDED_STATUS) | text()),
    )
    def test_invalid_start_message_wrong_status(self, message_dict, status):
        """
        A start message must have an C{ACTION_STATUS_FIELD} with the value
        C{STARTED_STATUS}, otherwise it's not a start message. If we receive
        such a message, raise an error.

        This test handles the case where the status field is present, but is
        not C{STARTED_STATUS}.
        """
        message = written_from_pmap(message_dict.update({ACTION_STATUS_FIELD: status}))
        self.assertRaises(InvalidStartMessage, WrittenAction.from_messages, message)

    @given(start_action_message_dicts, integers(min_value=2))
    def test_invalid_task_level_in_start_message(self, start_message_dict, i):
        """
        All messages in an action have a task level. The first message in an
        action must have a task level ending in C{1}, indicating that it's the
        first message.

        If we try to start an action with a message that has a task level that
        does not end in C{1}, raise an error.
        """
        new_level = start_message_dict[TASK_LEVEL_FIELD].append(i)
        message_dict = start_message_dict.set(TASK_LEVEL_FIELD, new_level)
        message = written_from_pmap(message_dict)
        self.assertRaises(InvalidStartMessage, WrittenAction.from_messages, message)

    @given(start_action_messages, message_dicts, text(), integers(min_value=1))
    def test_action_type_mismatch(self, start_message, end_message_dict, end_type, n):
        """
        The end message of an action must have the same C{ACTION_TYPE_FIELD} as
        the start message of an action. If we try to end an action with a
        message that has a different type, we raise an error.
        """
        assume(end_type != start_message.contents[ACTION_TYPE_FIELD])
        end_message = written_from_pmap(
            union(
                end_message_dict,
                {
                    ACTION_STATUS_FIELD: SUCCEEDED_STATUS,
                    ACTION_TYPE_FIELD: end_type,
                    TASK_UUID_FIELD: start_message.task_uuid,
                    TASK_LEVEL_FIELD: sibling_task_level(start_message, n),
                },
            )
        )
        self.assertRaises(
            WrongActionType,
            WrittenAction.from_messages,
            start_message,
            end_message=end_message,
        )

    @given(start_action_messages, message_dicts, integers(min_value=2))
    def test_successful_end(self, start_message, end_message_dict, n):
        """
        A L{WrittenAction} can be constructed with just a start message and an
        end message: in this case, an end message that indicates the action was
        successful.

        Such an action inherits the C{end_time} from the end message, and has
        a C{status} of C{SUCCEEDED_STATUS}.
        """
        end_message = written_from_pmap(
            union(
                end_message_dict,
                {
                    ACTION_STATUS_FIELD: SUCCEEDED_STATUS,
                    ACTION_TYPE_FIELD: start_message.contents[ACTION_TYPE_FIELD],
                    TASK_UUID_FIELD: start_message.task_uuid,
                    TASK_LEVEL_FIELD: sibling_task_level(start_message, n),
                },
            )
        )
        action = WrittenAction.from_messages(start_message, end_message=end_message)
        self.assertThat(
            action,
            MatchesStructure.byEquality(
                action_type=start_message.contents[ACTION_TYPE_FIELD],
                status=SUCCEEDED_STATUS,
                task_uuid=start_message.task_uuid,
                task_level=start_message.task_level.parent(),
                start_time=start_message.timestamp,
                children=pvector([]),
                end_time=end_message.timestamp,
                reason=None,
                exception=None,
            ),
        )

    @given(start_action_messages, message_dicts, text(), text(), integers(min_value=2))
    def test_failed_end(self, start_message, end_message_dict, exception, reason, n):
        """
        A L{WrittenAction} can be constructed with just a start message and an
        end message: in this case, an end message that indicates that the
        action failed.

        Such an action inherits the C{end_time} from the end message, has a
        C{status} of C{FAILED_STATUS}, and an C{exception} and C{reason} that
        match the raised exception.
        """
        end_message = written_from_pmap(
            union(
                end_message_dict,
                {
                    ACTION_STATUS_FIELD: FAILED_STATUS,
                    ACTION_TYPE_FIELD: start_message.contents[ACTION_TYPE_FIELD],
                    TASK_UUID_FIELD: start_message.task_uuid,
                    TASK_LEVEL_FIELD: sibling_task_level(start_message, n),
                    EXCEPTION_FIELD: exception,
                    REASON_FIELD: reason,
                },
            )
        )
        action = WrittenAction.from_messages(start_message, end_message=end_message)
        self.assertThat(
            action,
            MatchesStructure.byEquality(
                action_type=start_message.contents[ACTION_TYPE_FIELD],
                status=FAILED_STATUS,
                task_uuid=start_message.task_uuid,
                task_level=start_message.task_level.parent(),
                start_time=start_message.timestamp,
                children=pvector([]),
                end_time=end_message.timestamp,
                reason=reason,
                exception=exception,
            ),
        )

    @given(start_action_messages, message_dicts, integers(min_value=2))
    def test_end_has_no_status(self, start_message, end_message_dict, n):
        """
        If we try to end a L{WrittenAction} with a message that lacks an
        C{ACTION_STATUS_FIELD}, we raise an error, because it's not a valid
        end message.
        """
        assume(ACTION_STATUS_FIELD not in end_message_dict)
        end_message = written_from_pmap(
            union(
                end_message_dict,
                {
                    ACTION_TYPE_FIELD: start_message.contents[ACTION_TYPE_FIELD],
                    TASK_UUID_FIELD: start_message.task_uuid,
                    TASK_LEVEL_FIELD: sibling_task_level(start_message, n),
                },
            )
        )
        self.assertRaises(
            InvalidStatus,
            WrittenAction.from_messages,
            start_message,
            end_message=end_message,
        )

    # This test is slow, and when run under coverage on pypy on Travis won't
    # make the default of 5 examples. 1 is enough.
    @given(start_action_messages, lists(written_messages | written_actions))
    @settings(suppress_health_check=[HealthCheck.too_slow])
    def test_children(self, start_message, child_messages):
        """
        We can construct a L{WrittenAction} with child messages. These messages
        can be either L{WrittenAction}s or L{WrittenMessage}s. They are
        available in the C{children} field.
        """
        messages = [
            reparent_action(
                start_message.task_uuid,
                TaskLevel(level=sibling_task_level(start_message, i)),
                message,
            )
            for (i, message) in enumerate(child_messages, 2)
        ]
        action = WrittenAction.from_messages(start_message, messages)

        def task_level(m):
            return m.task_level

        self.assertEqual(sorted(messages, key=task_level), action.children)

    @given(start_action_messages, message_dicts)
    def test_wrong_task_uuid(self, start_message, child_message):
        """
        All child messages of an action must have the same C{task_uuid} as the
        action.
        """
        assume(child_message[TASK_UUID_FIELD] != start_message.task_uuid)
        message = written_from_pmap(child_message)
        self.assertRaises(
            WrongTask, WrittenAction.from_messages, start_message, v(message)
        )

    @given(start_action_messages, message_dicts)
    def test_wrong_task_level(self, start_message, child_message):
        """
        All child messages of an action must have a task level that is a direct
        child of the action's task level.
        """
        assume(
            not start_message.task_level.is_sibling_of(
                TaskLevel(level=child_message[TASK_LEVEL_FIELD])
            )
        )
        message = written_from_pmap(
            child_message.update({TASK_UUID_FIELD: start_message.task_uuid})
        )
        self.assertRaises(
            WrongTaskLevel, WrittenAction.from_messages, start_message, v(message)
        )

    @given(start_action_messages, message_dicts, message_dicts, integers(min_value=2))
    def test_duplicate_task_level(self, start_message, child1, child2, index):
        """
        If we try to add a child to an action that has a task level that's the
        same as the task level of an existing child, we raise an error.
        """
        parent_level = start_message.task_level.parent().level
        messages = [
            written_from_pmap(
                union(
                    child_message,
                    {
                        TASK_UUID_FIELD: start_message.task_uuid,
                        TASK_LEVEL_FIELD: parent_level.append(index),
                    },
                )
            )
            for child_message in [child1, child2]
        ]
        assume(messages[0] != messages[1])
        self.assertRaises(
            DuplicateChild, WrittenAction.from_messages, start_message, messages
        )


def make_error_extraction_tests(get_messages):
    """
    Create a test case class for testing extraction of fields from exceptions.

    @param get_messages: Callable that takes an exception instance, returns
        all message dictionaries generated by logging it.

    @return: ``TestCase`` subclass.
    """

    class ErrorFieldExtraction(TestCase):
        """
        Tests for extracting fields from exceptions in failed actions.
        """

        def test_matching_class(self):
            """
            If an exception fails an action and the exact type has registered
            extractor, extract errors using it.
            """

            class MyException(Exception):
                pass

            register_exception_extractor(MyException, lambda e: {"key": e.args[0]})
            exception = MyException("a value")
            [message] = get_messages(exception)
            assertContainsFields(self, message, {"key": "a value"})

        def test_subclass_falls_back_to_parent(self):
            """
            If an exception fails an action and the exact type has not been
            registered but the error is a subclass of a registered class,
            extract errors using it.
            """

            class MyException(Exception):
                pass

            class SubException(MyException):
                pass

            register_exception_extractor(MyException, lambda e: {"key": e.args[0]})
            [message] = get_messages(SubException("the value"))
            assertContainsFields(self, message, {"key": "the value"})

        def test_subclass_matches_first(self):
            """
            If both a superclass and base class have registered extractors, the
            more specific one is used.
            """

            class MyException(Exception):
                pass

            class SubException(MyException):
                pass

            class SubSubException(SubException):
                pass

            register_exception_extractor(MyException, lambda e: {"parent": e.args[0]})
            register_exception_extractor(SubException, lambda e: {"child": e.args[0]})
            [message] = get_messages(SubSubException("the value"))
            assertContainsFields(self, message, {"child": "the value"})

        def test_error_in_extracter(self):
            """
            If an error occurs in extraction, log the message as usual just
            without the extra fields, and an additional traceback.
            """

            class MyException(Exception):
                pass

            def extract(e):
                return e.nosuchattribute

            register_exception_extractor(MyException, extract)

            messages = get_failed_action_messages(MyException())
            assertContainsFields(
                self, messages[1], {"action_type": "sys:me", "action_status": "failed"}
            )
            assertContainsFields(self, messages[0], {"message_type": "eliot:traceback"})
            self.assertIn("nosuchattribute", str(messages[0]["reason"]))

        def test_environmenterror(self):
            """
            ``EnvironmentError`` has a registered extractor that extracts the
            errno.
            """
            [message] = get_messages(EnvironmentError(12, "oh noes"))
            assertContainsFields(self, message, {"errno": 12})

    return ErrorFieldExtraction


def get_failed_action_messages(exception):
    """
    Fail an action using the given exception.

    :return: Logged dictionaries from the exception failing an action.
    """
    action_type = ActionType("sys:me", [], [])
    logger = MemoryLogger()
    action = action_type.as_task(logger=logger)
    try:
        with action:
            raise exception
    except exception.__class__:
        pass
    logger.validate()
    return logger.messages[1:]


class FailedActionExtractionTests(
    make_error_extraction_tests(get_failed_action_messages)
):
    """
    Tests for error extraction in failed actions.
    """

    def test_regular_fields(self):
        """
        The normal failed action fields are still present when error
        extraction is used.
        """

        class MyException(Exception):
            pass

        register_exception_extractor(MyException, lambda e: {"key": e.args[0]})

        exception = MyException("because")
        messages = get_failed_action_messages(exception)
        assertContainsFields(
            self,
            messages[0],
            {
                "task_level": [2],
                "action_type": "sys:me",
                "action_status": "failed",
                "reason": "because",
                "exception": "eliot.tests.test_action.MyException",
            },
        )


class PreserveContextTests(TestCase):
    """
    Tests for L{preserve_context}.
    """

    def add(self, x, y):
        """
        Add two inputs.
        """
        Message.log(message_type="child")
        return x + y

    def test_no_context(self):
        """
        If C{preserve_context} is run outside an action context it just
        returns the same function.
        """
        wrapped = preserve_context(self.add)
        self.assertEqual(wrapped(2, 3), 5)

    def test_with_context_calls_underlying(self):
        """
        If run inside an Eliot context, the result of C{preserve_context} is
        the result of calling the underlying function.
        """
        with start_action(action_type="parent"):
            wrapped = preserve_context(self.add)
            self.assertEqual(wrapped(3, y=4), 7)

    @capture_logging(None)
    def test_with_context_preserves_context(self, logger):
        """
        If run inside an Eliot context, the result of C{preserve_context} runs
        the wrapped function within a C{eliot:task} which is a child of
        the original action.
        """
        with start_action(action_type="parent"):
            wrapped = preserve_context(lambda: self.add(3, 4))
        thread = Thread(target=wrapped)
        thread.start()
        thread.join()
        [tree] = Parser.parse_stream(logger.messages)
        root = tree.root()
        self.assertEqual(
            (
                root.action_type,
                root.children[0].action_type,
                root.children[0].children[0].contents[MESSAGE_TYPE_FIELD],
            ),
            ("parent", "eliot:remote_task", "child"),
        )

    def test_callable_only_once(self):
        """
        The result of C{preserve_context} can only be called once.
        """
        with start_action(action_type="parent"):
            wrapped = preserve_context(self.add)
        wrapped(1, 2)
        self.assertRaises(TooManyCalls, wrapped, 3, 4)


@log_call
def for_pickling():
    pass


class LogCallTests(TestCase):
    """Tests for log_call decorator."""

    def assert_logged(self, logger, action_type, expected_params, expected_result):
        """Assert that an action of given structure was logged."""
        [tree] = Parser.parse_stream(logger.messages)
        root = tree.root()
        self.assertEqual(root.action_type, action_type)
        message = dict(root.start_message.contents)
        for field in [ACTION_STATUS_FIELD, ACTION_TYPE_FIELD]:
            message.pop(field)
        self.assertEqual(message, expected_params)
        self.assertEqual(root.end_message.contents["result"], expected_result)
        self.assertEqual(root.status, SUCCEEDED_STATUS)

    @capture_logging(None)
    def test_no_args_return(self, logger):
        """
        C{@log_call} with no arguments logs return result, arguments, and has
        action type based on the action name.
        """

        @log_call
        def myfunc(x, y):
            return 4

        myfunc(2, 3)
        self.assert_logged(logger, self.id() + ".<locals>.myfunc", {"x": 2, "y": 3}, 4)

    @capture_logging(None)
    def test_exception(self, logger):
        """C{@log_call} with an exception logs a failed action."""

        @log_call
        def myfunc(x, y):
            1 / 0

        with self.assertRaises(ZeroDivisionError):
            myfunc(2, 4)

        [tree] = Parser.parse_stream(logger.messages)
        root = tree.root()
        self.assertIn("ZeroDivisionError", root.end_message.contents["exception"])
        self.assertEqual(root.status, FAILED_STATUS)

    @capture_logging(None)
    def test_action_type(self, logger):
        """C{@log_call} can take an action type."""

        @log_call(action_type="myaction")
        def myfunc(x, y):
            return 4

        myfunc(2, 3)
        self.assert_logged(logger, "myaction", {"x": 2, "y": 3}, 4)

    @capture_logging(None)
    def test_default_argument_given(self, logger):
        """C{@log_call} logs default arguments that were passed in."""

        @log_call
        def myfunc(x, y=1):
            return 4

        myfunc(2, y=5)
        self.assert_logged(logger, self.id() + ".<locals>.myfunc", {"x": 2, "y": 5}, 4)

    @capture_logging(None)
    def test_default_argument_missing(self, logger):
        """C{@log_call} logs default arguments that weren't passed in."""

        @log_call
        def myfunc(x, y=1):
            return 6

        myfunc(2)
        self.assert_logged(logger, self.id() + ".<locals>.myfunc", {"x": 2, "y": 1}, 6)

    @capture_logging(None)
    def test_star_args_kwargs(self, logger):
        """C{@log_call} logs star args and kwargs."""

        @log_call
        def myfunc(x, *y, **z):
            return 6

        myfunc(2, 3, 4, a=1, b=2)
        self.assert_logged(
            logger,
            self.id() + ".<locals>.myfunc",
            {"x": 2, "y": (3, 4), "z": {"a": 1, "b": 2}},
            6,
        )

    @capture_logging(None)
    def test_whitelist_args(self, logger):
        """C{@log_call} only includes whitelisted arguments."""

        @log_call(include_args=("x", "z"))
        def myfunc(x, y, z):
            return 6

        myfunc(2, 3, 4)
        self.assert_logged(logger, self.id() + ".<locals>.myfunc", {"x": 2, "z": 4}, 6)

    def test_wrong_whitelist_args(self):
        """If C{include_args} doesn't match function, raise an exception."""
        with self.assertRaises(ValueError):

            @log_call(include_args=["a", "x", "y"])
            def f(x, y):
                pass

    @capture_logging(None)
    def test_no_result(self, logger):
        """C{@log_call} can omit logging the result."""

        @log_call(include_result=False)
        def myfunc(x, y):
            return 6

        myfunc(2, 3)

        [tree] = Parser.parse_stream(logger.messages)
        root = tree.root()
        self.assertNotIn("result", root.end_message.contents)
        self.assertEqual(root.status, SUCCEEDED_STATUS)

    def test_pickleable(self):
        """Functions decorated with C{log_call} are pickleable.

        This is necessary for e.g. Dask usage.
        """
        self.assertIs(for_pickling, pickle.loads(pickle.dumps(for_pickling)))

    @capture_logging(None)
    def test_methods(self, logger):
        """self is not logged."""

        class C(object):
            @log_call
            def f(self, x):
                pass

        C().f(2)
        self.assert_logged(logger, self.id() + ".<locals>.C.f", {"x": 2}, None)


class IndividualMessageLogTests(TestCase):
    """Action.log() tests."""

    def test_log_creates_new_dictionary(self):
        """
        L{Action.log} creates a new dictionary on each call.

        This is important because we might mutate the dictionary in
        ``Logger.write``.
        """
        messages = []
        add_destination(messages.append)
        self.addCleanup(remove_destination, messages.append)

        with start_action(action_type="x") as action:
            action.log("mymessage", key=4)
            action.log(message_type="mymessage2", key=5)
        self.assertEqual(messages[1]["key"], 4)
        self.assertEqual(messages[2]["key"], 5)
        self.assertEqual(messages[1]["message_type"], "mymessage")
        self.assertEqual(messages[2]["message_type"], "mymessage2")

    @patch("time.time")
    def test_log_adds_timestamp(self, time_func):
        """
        L{Action.log} adds a C{"timestamp"} field to the dictionary written
        to the logger, with the current time in seconds since the epoch.
        """
        messages = []
        add_destination(messages.append)
        self.addCleanup(remove_destination, messages.append)

        time_func.return_value = timestamp = 1387299889.153187625
        with start_action(action_type="x") as action:
            action.log("mymessage", key=4)
        self.assertEqual(messages[-2]["message_type"], "mymessage")
        self.assertEqual(messages[-2]["timestamp"], timestamp)

    def test_part_of_action(self):
        """
        L{Action.log} adds the identification fields from the given
        L{Action} to the dictionary written to the logger.
        """
        messages = []
        add_destination(messages.append)
        self.addCleanup(remove_destination, messages.append)

        action = Action(None, "unique", TaskLevel(level=[37, 4]), "sys:thename")
        action.log("me", key=2)
        written = messages[0]
        del written["timestamp"]
        self.assertEqual(
            written,
            {
                "task_uuid": "unique",
                "task_level": [37, 4, 1],
                "key": 2,
                "message_type": "me",
            },
        )