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

from __future__ import unicode_literals

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

import six

if six.PY3:
    unicode = six.text_type

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{unicode()}.
        """
        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, unicode() 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 = unicode(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."""
        if six.PY2:
            # On Python 2 we don't include the module or class:
            action_type = action_type.split(".")[-1]
        [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)

    @skipIf(six.PY2, "Didn't bother implementing safety check on Python 2")
    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",
            },
        )
