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test_stateful.py
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test_stateful.py
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# This file is part of Hypothesis, which may be found at
# https://github.com/HypothesisWorks/hypothesis/
#
# Copyright the Hypothesis Authors.
# Individual contributors are listed in AUTHORS.rst and the git log.
#
# This Source Code Form is subject to the terms of the Mozilla Public License,
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
# obtain one at https://mozilla.org/MPL/2.0/.
import base64
from collections import defaultdict
import pytest
from _pytest.outcomes import Failed, Skipped
from pytest import raises
from hypothesis import __version__, reproduce_failure, seed, settings as Settings
from hypothesis.control import current_build_context
from hypothesis.database import ExampleDatabase
from hypothesis.errors import DidNotReproduce, Flaky, InvalidArgument, InvalidDefinition
from hypothesis.internal.compat import PYPY
from hypothesis.internal.entropy import deterministic_PRNG
from hypothesis.stateful import (
Bundle,
RuleBasedStateMachine,
consumes,
initialize,
invariant,
multiple,
precondition,
rule,
run_state_machine_as_test,
)
from hypothesis.strategies import binary, data, integers, just, lists
from tests.common.utils import capture_out, validate_deprecation
from tests.nocover.test_stateful import DepthMachine
NO_BLOB_SETTINGS = Settings(print_blob=False)
class MultipleRulesSameFuncMachine(RuleBasedStateMachine):
def myfunc(self, data):
print(data)
rule1 = rule(data=just("rule1data"))(myfunc)
rule2 = rule(data=just("rule2data"))(myfunc)
class PreconditionMachine(RuleBasedStateMachine):
num = 0
@rule()
def add_one(self):
self.num += 1
@rule()
def set_to_zero(self):
self.num = 0
@rule(num=integers())
@precondition(lambda self: self.num != 0)
def div_by_precondition_after(self, num):
self.num = num / self.num
@precondition(lambda self: self.num != 0)
@rule(num=integers())
def div_by_precondition_before(self, num):
self.num = num / self.num
TestPrecondition = PreconditionMachine.TestCase
TestPrecondition.settings = Settings(TestPrecondition.settings, max_examples=10)
def test_picks_up_settings_at_first_use_of_testcase():
assert TestPrecondition.settings.max_examples == 10
def test_multiple_rules_same_func():
test_class = MultipleRulesSameFuncMachine.TestCase
with capture_out() as o:
test_class().runTest()
output = o.getvalue()
assert "rule1data" in output
assert "rule2data" in output
def test_can_get_test_case_off_machine_instance():
assert DepthMachine().TestCase is DepthMachine().TestCase
assert DepthMachine().TestCase is not None
class FlakyDrawLessMachine(RuleBasedStateMachine):
@rule(d=data())
def action(self, d):
if current_build_context().is_final:
d.draw(binary(min_size=1, max_size=1))
else:
buffer = binary(min_size=1024, max_size=1024)
assert 0 not in buffer
def test_flaky_draw_less_raises_flaky():
with raises(Flaky):
FlakyDrawLessMachine.TestCase().runTest()
class FlakyStateMachine(RuleBasedStateMachine):
@rule()
def action(self):
assert current_build_context().is_final
def test_flaky_raises_flaky():
with raises(Flaky):
FlakyStateMachine.TestCase().runTest()
class FlakyRatchettingMachine(RuleBasedStateMachine):
ratchet = 0
@rule(d=data())
def action(self, d):
FlakyRatchettingMachine.ratchet += 1
n = FlakyRatchettingMachine.ratchet
d.draw(lists(integers(), min_size=n, max_size=n))
raise AssertionError
class MachineWithConsumingRule(RuleBasedStateMachine):
b1 = Bundle("b1")
b2 = Bundle("b2")
def __init__(self):
self.created_counter = 0
self.consumed_counter = 0
super().__init__()
@invariant()
def bundle_length(self):
assert len(self.bundle("b1")) == self.created_counter - self.consumed_counter
@rule(target=b1)
def populate_b1(self):
self.created_counter += 1
return self.created_counter
@rule(target=b2, consumed=consumes(b1))
def depopulate_b1(self, consumed):
self.consumed_counter += 1
return consumed
@rule(consumed=lists(consumes(b1)))
def depopulate_b1_multiple(self, consumed):
self.consumed_counter += len(consumed)
@rule(value1=b1, value2=b2)
def check(self, value1, value2):
assert value1 != value2
TestMachineWithConsumingRule = MachineWithConsumingRule.TestCase
def test_multiple():
none = multiple()
some = multiple(1, 2.01, "3", b"4", 5)
assert len(none.values) == 0 and len(some.values) == 5
assert set(some.values) == {1, 2.01, "3", b"4", 5}
class MachineUsingMultiple(RuleBasedStateMachine):
b = Bundle("b")
def __init__(self):
self.expected_bundle_length = 0
super().__init__()
@invariant()
def bundle_length(self):
assert len(self.bundle("b")) == self.expected_bundle_length
@rule(target=b, items=lists(elements=integers(), max_size=10))
def populate_bundle(self, items):
self.expected_bundle_length += len(items)
return multiple(*items)
@rule(target=b)
def do_not_populate(self):
return multiple()
TestMachineUsingMultiple = MachineUsingMultiple.TestCase
def test_multiple_variables_printed():
class ProducesMultiple(RuleBasedStateMachine):
b = Bundle("b")
@initialize(target=b)
def populate_bundle(self):
return multiple(1, 2)
@rule()
def fail_fast(self):
raise AssertionError
with raises(AssertionError) as err:
run_state_machine_as_test(ProducesMultiple)
# This is tightly coupled to the output format of the step printing.
# The first line is "Falsifying Example:..." the second is creating
# the state machine, the third is calling the "initialize" method.
assignment_line = err.value.__notes__[2]
# 'populate_bundle()' returns 2 values, so should be
# expanded to 2 variables.
assert assignment_line == "v1, v2 = state.populate_bundle()"
# Make sure MultipleResult is iterable so the printed code is valid.
# See https://github.com/HypothesisWorks/hypothesis/issues/2311
state = ProducesMultiple()
v1, v2 = state.populate_bundle()
with raises(AssertionError):
state.fail_fast()
def test_multiple_variables_printed_single_element():
# https://github.com/HypothesisWorks/hypothesis/issues/3236
class ProducesMultiple(RuleBasedStateMachine):
b = Bundle("b")
@initialize(target=b)
def populate_bundle(self):
return multiple(1)
@rule(b=b)
def fail_fast(self, b):
assert b != 1
with raises(AssertionError) as err:
run_state_machine_as_test(ProducesMultiple)
assignment_line = err.value.__notes__[2]
assert assignment_line == "(v1,) = state.populate_bundle()"
state = ProducesMultiple()
(v1,) = state.populate_bundle()
state.fail_fast((v1,)) # passes if tuple not unpacked
with raises(AssertionError):
state.fail_fast(v1)
def test_no_variables_printed():
class ProducesNoVariables(RuleBasedStateMachine):
b = Bundle("b")
@initialize(target=b)
def populate_bundle(self):
return multiple()
@rule()
def fail_fast(self):
raise AssertionError
with raises(AssertionError) as err:
run_state_machine_as_test(ProducesNoVariables)
# This is tightly coupled to the output format of the step printing.
# The first line is "Falsifying Example:..." the second is creating
# the state machine, the third is calling the "initialize" method.
assignment_line = err.value.__notes__[2]
# 'populate_bundle()' returns 0 values, so there should be no
# variable assignment.
assert assignment_line == "state.populate_bundle()"
def test_consumes_typecheck():
with pytest.raises(TypeError):
consumes(integers())
def test_ratchetting_raises_flaky():
with raises(Flaky):
FlakyRatchettingMachine.TestCase().runTest()
def test_empty_machine_is_invalid():
class EmptyMachine(RuleBasedStateMachine):
pass
with raises(InvalidDefinition):
EmptyMachine.TestCase().runTest()
def test_machine_with_no_terminals_is_invalid():
class NonTerminalMachine(RuleBasedStateMachine):
@rule(value=Bundle("hi"))
def bye(self, hi):
pass
with raises(InvalidDefinition):
NonTerminalMachine.TestCase().runTest()
def test_minimizes_errors_in_teardown():
counter = [0]
class Foo(RuleBasedStateMachine):
@initialize()
def init(self):
counter[0] = 0
@rule()
def increment(self):
counter[0] += 1
def teardown(self):
assert not counter[0]
with raises(AssertionError):
run_state_machine_as_test(Foo)
assert counter[0] == 1
class RequiresInit(RuleBasedStateMachine):
def __init__(self, threshold):
super().__init__()
self.threshold = threshold
@rule(value=integers())
def action(self, value):
if value > self.threshold:
raise ValueError(f"{value} is too high")
def test_can_use_factory_for_tests():
with raises(ValueError):
run_state_machine_as_test(
lambda: RequiresInit(42), settings=Settings(max_examples=100)
)
class FailsEventually(RuleBasedStateMachine):
def __init__(self):
super().__init__()
self.counter = 0
@rule()
def increment(self):
self.counter += 1
assert self.counter < 10
FailsEventually.TestCase.settings = Settings(stateful_step_count=5)
def test_can_explicitly_pass_settings():
run_state_machine_as_test(FailsEventually)
try:
FailsEventually.TestCase.settings = Settings(
FailsEventually.TestCase.settings, stateful_step_count=15
)
run_state_machine_as_test(
FailsEventually, settings=Settings(stateful_step_count=2)
)
finally:
FailsEventually.TestCase.settings = Settings(
FailsEventually.TestCase.settings, stateful_step_count=5
)
def test_settings_argument_is_validated():
with pytest.raises(InvalidArgument):
run_state_machine_as_test(FailsEventually, settings=object())
def test_runner_that_checks_factory_produced_a_machine():
with pytest.raises(InvalidArgument):
run_state_machine_as_test(object)
def test_settings_attribute_is_validated():
real_settings = FailsEventually.TestCase.settings
try:
FailsEventually.TestCase.settings = object()
with pytest.raises(InvalidArgument):
run_state_machine_as_test(FailsEventually)
finally:
FailsEventually.TestCase.settings = real_settings
def test_saves_failing_example_in_database():
db = ExampleDatabase(":memory:")
with raises(AssertionError):
run_state_machine_as_test(
DepthMachine, settings=Settings(database=db, max_examples=100)
)
assert any(list(db.data.values()))
def test_can_run_with_no_db():
with deterministic_PRNG(), raises(AssertionError):
run_state_machine_as_test(
DepthMachine, settings=Settings(database=None, max_examples=10_000)
)
def test_stateful_double_rule_is_forbidden(recwarn):
with pytest.raises(InvalidDefinition):
class DoubleRuleMachine(RuleBasedStateMachine):
@rule(num=just(1))
@rule(num=just(2))
def whatevs(self, num):
pass
def test_can_explicitly_call_functions_when_precondition_not_satisfied():
class BadPrecondition(RuleBasedStateMachine):
def __init__(self):
super().__init__()
@precondition(lambda self: False)
@rule()
def test_blah(self):
raise ValueError()
@rule()
def test_foo(self):
self.test_blah()
with pytest.raises(ValueError):
run_state_machine_as_test(BadPrecondition)
def test_invariant():
"""If an invariant raise an exception, the exception is propagated."""
class Invariant(RuleBasedStateMachine):
def __init__(self):
super().__init__()
@invariant()
def test_blah(self):
raise ValueError()
@rule()
def do_stuff(self):
pass
with pytest.raises(ValueError):
run_state_machine_as_test(Invariant)
def test_no_double_invariant():
"""The invariant decorator can't be applied multiple times to a single
function."""
with raises(InvalidDefinition):
class Invariant(RuleBasedStateMachine):
def __init__(self):
super().__init__()
@invariant()
@invariant()
def test_blah(self):
pass
@rule()
def do_stuff(self):
pass
def test_invariant_precondition():
"""If an invariant precodition isn't met, the invariant isn't run.
The precondition decorator can be applied in any order.
"""
class Invariant(RuleBasedStateMachine):
def __init__(self):
super().__init__()
@invariant()
@precondition(lambda _: False)
def an_invariant(self):
raise ValueError()
@precondition(lambda _: False)
@invariant()
def another_invariant(self):
raise ValueError()
@rule()
def do_stuff(self):
pass
run_state_machine_as_test(Invariant)
@pytest.mark.parametrize(
"decorators",
[
(invariant(), rule()),
(rule(), invariant()),
(invariant(), initialize()),
(initialize(), invariant()),
(invariant(), precondition(lambda self: True), rule()),
(rule(), precondition(lambda self: True), invariant()),
(precondition(lambda self: True), invariant(), rule()),
(precondition(lambda self: True), rule(), invariant()),
],
ids=lambda x: "-".join(f.__qualname__.split(".")[0] for f in x),
)
def test_invariant_and_rule_are_incompatible(decorators):
"""It's an error to apply @invariant and @rule to the same method."""
def method(self):
pass
for d in decorators[:-1]:
method = d(method)
with pytest.raises(InvalidDefinition):
decorators[-1](method)
def test_invalid_rule_argument():
"""Rule kwargs that are not a Strategy are expected to raise an InvalidArgument error."""
with pytest.raises(InvalidArgument):
class InvalidRuleMachine(RuleBasedStateMachine):
@rule(strategy=object())
def do_stuff(self):
pass
def test_invalid_initialize_argument():
"""Initialize kwargs that are not a Strategy are expected to raise an InvalidArgument error."""
with pytest.raises(InvalidArgument):
class InvalidInitialize(RuleBasedStateMachine):
@initialize(strategy=object())
def initialize(self):
pass
def test_multiple_invariants():
"""If multiple invariants are present, they all get run."""
class Invariant(RuleBasedStateMachine):
def __init__(self):
super().__init__()
self.first_invariant_ran = False
@invariant()
def invariant_1(self):
self.first_invariant_ran = True
@precondition(lambda self: self.first_invariant_ran)
@invariant()
def invariant_2(self):
raise ValueError()
@rule()
def do_stuff(self):
pass
with pytest.raises(ValueError):
run_state_machine_as_test(Invariant)
def test_explicit_invariant_call_with_precondition():
"""Invariants can be called explicitly even if their precondition is not
satisfied."""
class BadPrecondition(RuleBasedStateMachine):
def __init__(self):
super().__init__()
@precondition(lambda self: False)
@invariant()
def test_blah(self):
raise ValueError()
@rule()
def test_foo(self):
self.test_blah()
with pytest.raises(ValueError):
run_state_machine_as_test(BadPrecondition)
def test_invariant_checks_initial_state_if_no_initialize_rules():
"""Invariants are checked before any rules run."""
class BadPrecondition(RuleBasedStateMachine):
def __init__(self):
super().__init__()
self.num = 0
@invariant()
def test_blah(self):
if self.num == 0:
raise ValueError()
@rule()
def test_foo(self):
self.num += 1
with pytest.raises(ValueError):
run_state_machine_as_test(BadPrecondition)
def test_invariant_failling_present_in_falsifying_example():
@Settings(print_blob=False)
class BadInvariant(RuleBasedStateMachine):
@initialize()
def initialize_1(self):
pass
@invariant()
def invariant_1(self):
raise ValueError()
@rule()
def rule_1(self):
pass
with pytest.raises(ValueError) as err:
run_state_machine_as_test(BadInvariant)
result = "\n".join(err.value.__notes__)
assert (
result
== """
Falsifying example:
state = BadInvariant()
state.initialize_1()
state.invariant_1()
state.teardown()
""".strip()
)
def test_invariant_present_in_falsifying_example():
@Settings(print_blob=False)
class BadRuleWithGoodInvariants(RuleBasedStateMachine):
def __init__(self):
super().__init__()
self.num = 0
@initialize()
def initialize_1(self):
pass
@invariant(check_during_init=True)
def invariant_1(self):
pass
@invariant(check_during_init=False)
def invariant_2(self):
pass
@precondition(lambda self: self.num > 0)
@invariant()
def invariant_3(self):
pass
@rule()
def rule_1(self):
self.num += 1
if self.num == 2:
raise ValueError()
with pytest.raises(ValueError) as err:
run_state_machine_as_test(BadRuleWithGoodInvariants)
result = "\n".join(err.value.__notes__[:-1]) # omit location - absolute paths vary
assert (
result
== """\
Falsifying example:
state = BadRuleWithGoodInvariants()
state.invariant_1()
state.initialize_1()
state.invariant_1()
state.invariant_2()
state.rule_1()
state.invariant_1()
state.invariant_2()
state.invariant_3()
state.rule_1()
state.teardown()"""
+ """
Explanation:
These lines were always and only run by failing examples:"""
* (not PYPY)
)
def test_always_runs_at_least_one_step():
class CountSteps(RuleBasedStateMachine):
def __init__(self):
super().__init__()
self.count = 0
@rule()
def do_something(self):
self.count += 1
def teardown(self):
assert self.count > 0
run_state_machine_as_test(CountSteps)
def test_removes_needless_steps():
"""Regression test from an example based on
tests/nocover/test_database_agreement.py, but without the expensive bits.
Comparing two database implementations in which deletion is broken, so as
soon as a key/value pair is successfully deleted the test will now fail if
you ever check that key.
The main interesting feature of this is that it has a lot of
opportunities to generate keys and values before it actually fails,
but will still fail with very high probability.
"""
@Settings(derandomize=True, max_examples=1000, deadline=None)
class IncorrectDeletion(RuleBasedStateMachine):
def __init__(self):
super().__init__()
self.__saved = defaultdict(set)
self.__deleted = defaultdict(set)
keys = Bundle("keys")
values = Bundle("values")
@rule(target=keys, k=binary())
def k(self, k):
return k
@rule(target=values, v=binary())
def v(self, v):
return v
@rule(k=keys, v=values)
def save(self, k, v):
self.__saved[k].add(v)
@rule(k=keys, v=values)
def delete(self, k, v):
if v in self.__saved[k]:
self.__deleted[k].add(v)
@rule(k=keys)
def values_agree(self, k):
assert not self.__deleted[k]
with pytest.raises(AssertionError) as err:
run_state_machine_as_test(IncorrectDeletion)
result = "\n".join(err.value.__notes__)
assert result.count(" = state.k(") == 1
assert result.count(" = state.v(") == 1
def test_prints_equal_values_with_correct_variable_name():
@Settings(max_examples=100)
class MovesBetweenBundles(RuleBasedStateMachine):
b1 = Bundle("b1")
b2 = Bundle("b2")
@rule(target=b1)
def create(self):
return []
@rule(target=b2, source=b1)
def transfer(self, source):
return source
@rule(source=b2)
def fail(self, source):
raise AssertionError
with pytest.raises(AssertionError) as err:
run_state_machine_as_test(MovesBetweenBundles)
result = "\n".join(err.value.__notes__)
for m in ["create", "transfer", "fail"]:
assert result.count("state." + m) == 1
assert "v1 = state.create()" in result
assert "v2 = state.transfer(source=v1)" in result
assert "state.fail(source=v2)" in result
def test_initialize_rule():
@Settings(max_examples=1000)
class WithInitializeRules(RuleBasedStateMachine):
initialized = []
@initialize()
def initialize_a(self):
self.initialized.append("a")
@initialize()
def initialize_b(self):
self.initialized.append("b")
@initialize()
def initialize_c(self):
self.initialized.append("c")
@rule()
def fail_fast(self):
raise AssertionError
with pytest.raises(AssertionError) as err:
run_state_machine_as_test(WithInitializeRules)
assert set(WithInitializeRules.initialized[-3:]) == {"a", "b", "c"}
result = err.value.__notes__[1:]
assert result[0] == "state = WithInitializeRules()"
# Initialize rules call order is shuffled
assert {result[1], result[2], result[3]} == {
"state.initialize_a()",
"state.initialize_b()",
"state.initialize_c()",
}
assert result[4] == "state.fail_fast()"
assert result[5] == "state.teardown()"
def test_initialize_rule_populate_bundle():
class WithInitializeBundleRules(RuleBasedStateMachine):
a = Bundle("a")
@initialize(target=a, dep=just("dep"))
def initialize_a(self, dep):
return f"a v1 with ({dep})"
@rule(param=a)
def fail_fast(self, param):
raise AssertionError
WithInitializeBundleRules.TestCase.settings = NO_BLOB_SETTINGS
with pytest.raises(AssertionError) as err:
run_state_machine_as_test(WithInitializeBundleRules)
result = "\n".join(err.value.__notes__)
assert (
result
== """
Falsifying example:
state = WithInitializeBundleRules()
v1 = state.initialize_a(dep='dep')
state.fail_fast(param=v1)
state.teardown()
""".strip()
)
def test_initialize_rule_dont_mix_with_precondition():
with pytest.raises(InvalidDefinition) as exc:
class BadStateMachine(RuleBasedStateMachine):
@precondition(lambda self: True)
@initialize()
def initialize(self):
pass
assert "An initialization rule cannot have a precondition." in str(exc.value)
# Also test decorator application in reverse order
with pytest.raises(InvalidDefinition) as exc:
class BadStateMachineReverseOrder(RuleBasedStateMachine):
@initialize()
@precondition(lambda self: True)
def initialize(self):
pass
assert "An initialization rule cannot have a precondition." in str(exc.value)
def test_initialize_rule_dont_mix_with_regular_rule():
with pytest.raises(InvalidDefinition) as exc:
class BadStateMachine(RuleBasedStateMachine):
@rule()
@initialize()
def initialize(self):
pass
assert "A function cannot be used for two distinct rules." in str(exc.value)
def test_initialize_rule_cannot_be_double_applied():
with pytest.raises(InvalidDefinition) as exc:
class BadStateMachine(RuleBasedStateMachine):
@initialize()
@initialize()
def initialize(self):
pass
assert "A function cannot be used for two distinct rules." in str(exc.value)
def test_initialize_rule_in_state_machine_with_inheritance():
class ParentStateMachine(RuleBasedStateMachine):
initialized = []
@initialize()
def initialize_a(self):
self.initialized.append("a")
class ChildStateMachine(ParentStateMachine):
@initialize()
def initialize_b(self):
self.initialized.append("b")
@rule()
def fail_fast(self):
raise AssertionError
with pytest.raises(AssertionError) as err:
run_state_machine_as_test(ChildStateMachine)
assert set(ChildStateMachine.initialized[-2:]) == {"a", "b"}
result = err.value.__notes__[1:]
assert result[0] == "state = ChildStateMachine()"
# Initialize rules call order is shuffled
assert {result[1], result[2]} == {"state.initialize_a()", "state.initialize_b()"}
assert result[3] == "state.fail_fast()"
assert result[4] == "state.teardown()"
def test_can_manually_call_initialize_rule():
class StateMachine(RuleBasedStateMachine):
initialize_called_counter = 0
@initialize()
def initialize(self):
self.initialize_called_counter += 1
@rule()
def fail_eventually(self):
self.initialize()
assert self.initialize_called_counter <= 2
StateMachine.TestCase.settings = NO_BLOB_SETTINGS
with pytest.raises(AssertionError) as err:
run_state_machine_as_test(StateMachine)
result = "\n".join(err.value.__notes__)
assert (
result
== """
Falsifying example:
state = StateMachine()
state.initialize()
state.fail_eventually()
state.fail_eventually()
state.teardown()
""".strip()
)
def test_steps_printed_despite_pytest_fail():
# Test for https://github.com/HypothesisWorks/hypothesis/issues/1372
@Settings(print_blob=False)
class RaisesProblem(RuleBasedStateMachine):
@rule()
def oops(self):
pytest.fail()
with pytest.raises(Failed) as err:
run_state_machine_as_test(RaisesProblem)
assert (
"\n".join(err.value.__notes__).strip()
== """
Falsifying example:
state = RaisesProblem()
state.oops()
state.teardown()""".strip()
)
def test_steps_not_printed_with_pytest_skip(capsys):
class RaisesProblem(RuleBasedStateMachine):
@rule()
def skip_whole_test(self):
pytest.skip()
with pytest.raises(Skipped):
run_state_machine_as_test(RaisesProblem)