32 questions · Software Testing · All types, answers revealed
When using the 'unittest' framework, which method is executed exactly once before any test methods in a class are run?
This is the correct class method to run setup code once for the entire class.
Why this answer
The 'setUpClass' method is a class method that runs once before all tests in the class, whereas 'setUp' runs before each individual test.
Which THREE of the following are common benefits of using a mocking framework in testing?
Core benefit of unit testing.
Why this answer
Mocking isolates the unit under test, speeds up tests by replacing I/O, and enables testing of error paths that are hard to trigger.
In 'unittest.mock', when you want to return a specific value based on the input arguments of a mocked function, which property should be configured?
Assigning a function to side_effect allows dynamic response based on arguments.
Why this answer
The 'side_effect' property allows you to assign a function that computes the return value dynamically based on arguments, unlike 'return_value' which is static.
Which THREE of the following are valid scopes for a pytest fixture?
Default scope.
Why this answer
The valid scopes in pytest are function, class, module, package, and session.
Which TWO of the following are true regarding 'unittest' test suites?
Inheritance is required for the framework to pick up the tests.
Why this answer
Suites can be built using TestLoader, and tests are aggregated from classes inheriting from unittest.TestCase.
Which pytest feature allows you to run the same test multiple times with different sets of inputs?
This is the built-in way to run tests with multiple inputs.
Why this answer
Parametrization using @pytest.mark.parametrize allows a test function to be executed with varying data sets.
Which THREE features are provided by 'pytest' but NOT by the standard 'unittest' framework?
pytest has this built-in.
Why this answer
pytest offers native parametrization, powerful fixture injection, and automatic test discovery without boilerplate classes.
Which TWO of the following are valid ways to run tests?
Standard unittest module command.
Why this answer
Both 'pytest' and 'python -m unittest' are the standard command-line ways to execute Python test suites.
Which TWO of the following are valid ways to assert that a mock was NOT called?
Explicit method for this purpose.
Why this answer
assert_not_called and assert_called_count(0) are both valid methods to confirm a mock was not interacted with.
Which of these is the most effective way to test a function that uses 'time.sleep()' without actually waiting?
Mocking the function avoids the delay entirely.
Why this answer
Mocking the 'time.sleep' function prevents it from actually executing the sleep command, making tests run faster.
Which TWO of the following pytest command-line options allow for filtering which tests are run?
Filters tests by markers.
Why this answer
-k allows filtering by substring and -m allows filtering by markers.
Which THREE attributes of 'unittest.mock.Mock' allow for verifying call interactions?
Stores a list of all call arguments.
Why this answer
call_args, call_args_list, and method_calls provide metadata about how the mock was interacted with during a test.
Which command-line argument shows the values of local variables in the event of a test failure?
This flag is specifically for viewing local variables.
Why this answer
The --showlocals flag instructs pytest to display local variables in the traceback output upon failure.
Which THREE of the following are true regarding the use of 'unittest.mock.patch'?
Handy for selective patching.
Why this answer
Patching can be used as a decorator, a context manager, or manually with 'start' and 'stop'.
When using 'unittest', how do you ensure that a teardown method runs even if the test method raises an exception?
unittest handles this by design after each test method.
Why this answer
The 'tearDown' method is guaranteed to run by the unittest framework regardless of the test outcome, assuming setup succeeded.
In pytest, how can you skip a test based on the operating system platform?
This correctly evaluates the platform condition at collection time.
Why this answer
The @pytest.mark.skipif decorator allows for conditional skipping based on expressions like sys.platform.
What is the purpose of the 'autospec' argument in 'patch'?
autospec enforces signature and method existence compliance.
Why this answer
autospec ensures the mock has the same attributes and methods as the object it is replacing, preventing tests from passing when they call non-existent methods.
Which of the following is a valid way to run all tests in a directory using pytest?
By default, pytest executes all discovered tests.
Why this answer
Running 'pytest' without arguments in a directory defaults to discovering and executing all tests in that directory tree.
What command-line flag is used in pytest to stop the test suite execution after the first failure?
-x is the correct flag for exiting on the first failure.
Why this answer
The -x (or --exitfirst) flag causes pytest to exit immediately upon the first failed test.
Which 'unittest' assertion is best suited to verify that two floating-point numbers are equal within a certain tolerance?
This supports a 'places' or 'delta' argument for tolerance.
Why this answer
assertAlmostEqual is specifically designed to handle floating-point precision issues by comparing values within a specified delta.
How do you check how many times a mock object was called?
This is the correct property for counting calls.
Why this answer
The 'call_count' attribute on a MagicMock or Mock object keeps track of the number of times it has been called.
You need to mock an object that is imported into a module. Which patch strategy correctly replaces the object where it is used?
Patching the lookup target ensures the module uses the mock.
Why this answer
You must patch the object in the namespace where it is imported (the destination), not where it is defined, to ensure the replacement takes effect.
You are writing a pytest fixture that opens a database connection. Which scope should you use to ensure the connection is created once per module, rather than once per test function?
This runs the fixture setup once per module execution.
Why this answer
The 'scope' argument in the @pytest.fixture decorator controls the lifetime. 'module' scope runs the fixture once per module.
What is the result of using 'unittest.mock.patch.object' instead of 'unittest.mock.patch'?
It is specific for patching existing attributes on an object.
Why this answer
patch.object is used to patch a specific attribute on an object, rather than patching an object by its string path.
Which TWO of the following are valid ways to pass data into a pytest test function?
pytest automatically injects fixtures based on argument names.
Why this answer
Fixtures and parametrization are the standard ways to inject data into pytest functions.
When asserting that a mock was called with specific arguments, which method should be used to verify the call history?
This confirms the arguments of the call.
Why this answer
assert_called_with is the standard method for verifying the most recent call or the specific instance of a call.
You are writing a pytest plugin and need to access the command-line options. Which hook should you implement in conftest.py?
This hook is specifically for adding custom command-line options.
Why this answer
pytest_addoption is the hook used to register custom command-line options for the pytest session.
What is the purpose of 'pytest.mark.xfail'?
xfail signals that failure is expected.
Why this answer
It marks a test as expected to fail, allowing the build to pass even if the test fails.
You are refactoring a legacy module and want to use 'pytest' to check if a function raises a specific custom exception. Which construct is most idiomatic?
pytest.raises is the correct context manager for exception testing.
Why this answer
The 'pytest.raises' context manager is the standard way to verify that a block of code raises a specific exception type.
When using 'unittest.mock.MagicMock', what happens when you access an attribute that hasn't been defined?
This allows for recursive chaining of mocks.
Why this answer
MagicMock instances automatically create new MagicMock objects when you access previously undefined attributes.
In pytest, how can you dynamically add a marker to a test at runtime?
This hook provides access to the items and their markers before execution.
Why this answer
The 'pytest_collection_modifyitems' hook allows you to modify the collected tests, including adding markers dynamically.
In pytest, how can you share a fixture across multiple files?
conftest.py is the standard file for shared fixtures.
Why this answer
Placing the fixture in a 'conftest.py' file within a directory makes it available to all test files in that directory and subdirectories.
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