@pytest.mark.parametrize decorator - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the @pytest.mark.parametrize decorator in pytest?

It allows you to run the same test function multiple times with different input values, making tests more efficient and easier to maintain.

beginner

How do you specify multiple sets of input values using @pytest.mark.parametrize?

You provide a string of comma-separated parameter names and a list of tuples with values for each test run.

beginner

Example: What will happen when this test runs?<br><pre>import pytest

@pytest.mark.parametrize('x, y, expected', [(1, 2, 3), (4, 5, 9)])
def test_add(x, y, expected):
    assert x + y == expected</pre>

The test test_add will run twice: once with (1, 2, 3) and once with (4, 5, 9). Both runs check if x + y equals expected.

intermediate

Can @pytest.mark.parametrize be used to test edge cases and why is this useful?

Yes, it helps test many edge cases easily by running the same test with different inputs, improving test coverage without writing many separate tests.

intermediate

What happens if one of the parameter sets in @pytest.mark.parametrize causes the test to fail?

Only that specific test run fails, while others continue. This helps identify which input caused the failure clearly.

What does @pytest.mark.parametrize do?

A Groups tests into a suite

B Skips a test

C Marks a test as expected to fail

D Runs a test multiple times with different inputs

The decorator runs the same test function multiple times with different sets of parameters.

How do you pass parameters to @pytest.mark.parametrize?

A As environment variables

B As a string of parameter names and a list of tuples with values

C As a single list of values

D As a dictionary of key-value pairs

You specify parameter names as a string and provide a list of tuples with values for each test run.

If a test with @pytest.mark.parametrize fails for one input set, what happens?

A Only that input set's test fails; others run normally

B All tests stop immediately

C All tests fail

D The test is skipped

Each parameter set runs as a separate test case; failure in one does not stop others.

Which of these is a correct use of @pytest.mark.parametrize?

A @pytest.mark.parametrize([1,2,3])

B @pytest.mark.parametrize('a', 5)

C @pytest.mark.parametrize('a,b', [(1,2), (3,4)])

D @pytest.mark.parametrize('a,b,c')

Option C correctly specifies parameter names and a list of tuples with values.

Why is @pytest.mark.parametrize helpful for testing?

A It reduces code duplication by running one test with many inputs

B It makes tests run faster by skipping some

C It automatically fixes bugs

D It hides test failures

It helps write fewer tests by reusing the same test logic with different data.

Explain how to use @pytest.mark.parametrize to test a function with multiple input sets.

Think about how you tell pytest which inputs to use for each test run.

Describe the benefits of using @pytest.mark.parametrize in your test suite.

Consider how it helps when you want to test many input values without writing many tests.