Question 1

What is PyTest, and what makes it preferred over Python's built-in `unittest` library?

Accepted Answer

PyTest is a robust, open-source Python testing framework. Key advantages over `unittest` include:
1. Simple syntax: No need to wrap tests in classes; tests are simple functions prefixed with `test_`.
2. Plain `assert` statements: No need for helper methods like `self.assertEqual()`.
3. Powerful Fixtures: High-speed modular dependency sharing.
4. Rich plugin ecosystem.

Question 2

How does PyTest handle assertions? What is assertion introspection?

Accepted Answer

PyTest allows using Python's standard `assert` keyword. During test runs, PyTest uses assertion introspection to rewrite assertion statements, capturing detailed execution outputs and displaying values of variables on failures.

Question 3

What are PyTest Fixtures, and how are they defined?

Accepted Answer

Fixtures are helper functions that run before tests to set up databases, configure clients, or prepare mock variables. They are defined by annotating functions with `@pytest.fixture`. Tests consume them by listing the fixture name as a parameter.
Code Example:
import pytest

@pytest.fixture
def db_connection():
    db = connect()
    return db

def test_query(db_connection):
    result = db_connection.query("SELECT...")
    assert result is not None

Question 4

What is `conftest.py` in PyTest?

Accepted Answer

`conftest.py` is a special configuration file in PyTest. It is used to define global fixtures, plugins, and hooks that can be shared across all test files in the directory tree without needing explicit imports.

Question 5

Explain the scope of a PyTest Fixture.

Accepted Answer

Fixtures can be scoped to control how often they are created:
1. `function` (Default): Created once per test function run.
2. `class`: Created once per test class run.
3. `module`: Created once per test file/module run.
4. `package`: Created once per directory package run.
5. `session`: Created once per test suite execution.

Question 6

How do you perform teardown or cleanup actions in a PyTest Fixture?

Accepted Answer

Teardown is handled using the **`yield`** statement instead of `return`. Code before `yield` runs before the test (setup), and code after `yield` runs after the test finishes (teardown).
Code Example:
@pytest.fixture
def file_setup():
    f = open("temp.txt", "w")
    yield f # Setup returns here
    # Teardown starts here
    f.close()
    os.remove("temp.txt")

Question 7

Explain Parameterized Tests in PyTest.

Accepted Answer

You parameterize tests using the `@pytest.mark.parametrize` decorator, allowing running a test function with varying input datasets.
Code Example:
@pytest.mark.parametrize("input_val, expected", [
    (1, 2),
    (2, 4),
    (3, 6)
])
def test_double(input_val, expected):
    assert double(input_val) == expected

Question 8

What are PyTest Markers?

Accepted Answer

Markers are decorators used to categorize tests or configure test behaviors. Built-in markers include `@pytest.mark.skip` (skips test), `@pytest.mark.skipif` (skips on condition), and `@pytest.mark.xfail` (indicates an expected failure). You can also declare custom markers (e.g. `@pytest.mark.slow`).

Question 9

How do you test that a function raises an exception in PyTest?

Accepted Answer

You test exceptions using the `pytest.raises()` context manager, wrapping the target function code block.
Code Example:
def test_exception():
    with pytest.raises(ValueError) as excinfo:
        raise_error()
    assert "invalid argument" in str(excinfo.value)

Question 10

What is PyTest autouse fixture?

Accepted Answer

An autouse fixture is configured by passing `autouse=True` in the fixture decorator. This forces the fixture to run automatically for all tests within its scope without needing to list it as a parameter in test functions, useful for database resets.

Question 11

How do you execute specific tests in PyTest?

Accepted Answer

You can filter tests by name or marker using the CLI:
- Run specific file: `pytest test_file.py`
- Filter by name query: `pytest -k "test_login"`
- Filter by marker: `pytest -m slow`

Question 12

What is `pytest.ini`?

Accepted Answer

`pytest.ini` is the primary configuration file for PyTest. It defines default command-line flags (addopts), registers custom markers, specifies test search directories, and sets logging configurations.

Question 13

What is the difference between `pytest.fixture(scope="session")` and global variables?

Accepted Answer

A session-scoped fixture is run lazily (only when first requested) and safely caches the return value across all tests. It also supports clean teardown hooks. Global variables are resolved immediately on import, do not support teardown, and can easily result in state leaks across files.

Question 14

How do you mock or patch dependencies in PyTest?

Accepted Answer

Mocking is handled using the `unittest.mock` library, or the `pytest-mock` plugin which provides the `mocker` fixture, managing mocks safely without needing context managers.
Code Example:
def test_api(mocker):
    mock_get = mocker.patch('requests.get')
    mock_get.return_value.status_code = 200

Question 15

What is the difference between `xfail` and `skip` markers?

Accepted Answer

`skip` completely bypasses test execution. `xfail` executes the test, but if it fails, PyTest reports it as expected (XFAIL) and does not count it as a suite failure. If it passes, it reports it as unexpected pass (XPASS).

Question 16

Explain PyTest fixtures dependency injection (fixtures using other fixtures).

Accepted Answer

PyTest fixtures support dependency injection. A fixture can consume other fixtures by listing them as arguments in its definition, creating modular dependencies.

Question 17

What is the `capfd` or `capsys` fixture in PyTest?

Accepted Answer

`capsys` and `capfd` are built-in fixtures that capture writes to standard output (`sys.stdout`) and standard error (`sys.stderr`) during test execution, allowing developers to assert console prints.

Question 18

How do you generate HTML test reports in PyTest?

Accepted Answer

HTML reports can be generated using the `pytest-html` plugin by passing the `--html` flag in the command line.
Code Example:
pytest --html=report.html

Question 19

What are pytest plugins? List common ones.

Accepted Answer

Plugins are packages that extend PyTest capabilities. Common ones include:
- `pytest-cov`: Measures code coverage.
- `pytest-mock`: Simple mocking fixture wrapper.
- `pytest-django`: Integrates with Django models.
- `pytest-xdist`: Runs tests in parallel across multiple CPU cores.

Question 20

Explain the `pytest-xdist` plugin and parallel execution.

Accepted Answer

`pytest-xdist` allows parallel test execution. It distributes test files across multiple local CPU worker cores, significantly reducing execution times for large test suites.
Code Example:
pytest -n auto # Auto-detects and uses all available CPU cores

PyTest Python Testing Interview

Difficulty Filters

Tools & Options

What is PyTest, and what makes it preferred over Python's built-in `unittest` library?

How does PyTest handle assertions? What is assertion introspection?

What are PyTest Fixtures, and how are they defined?

What is `conftest.py` in PyTest?

Explain the scope of a PyTest Fixture.

How do you perform teardown or cleanup actions in a PyTest Fixture?

Explain Parameterized Tests in PyTest.

What are PyTest Markers?

How do you test that a function raises an exception in PyTest?

What is PyTest autouse fixture?

How do you execute specific tests in PyTest?

What is `pytest.ini`?

What is the difference between `pytest.fixture(scope="session")` and global variables?

How do you mock or patch dependencies in PyTest?

What is the difference between `xfail` and `skip` markers?

Explain PyTest fixtures dependency injection (fixtures using other fixtures).

What is the `capfd` or `capsys` fixture in PyTest?

How do you generate HTML test reports in PyTest?

What are pytest plugins? List common ones.

Explain the `pytest-xdist` plugin and parallel execution.

Explore Related Tools

Bootstrap 5 Forms: Complete Guide to Controls, Layouts & Validation

Bootstrap 5 Text Alignment: Start, Center, End & Responsive Classes

Bootstrap 5 Text Colors: Primary, Success, Danger & Opacity Classes

Bootstrap 5 Responsive Video Tutorial: YouTube, Vimeo & Ratio Guide

Bootstrap 5 Input Group: Addons, Buttons & Form Controls

Bootstrap 5 Spinners: Loading Indicators, Colors & Sizes

Follow Us

Our Tools

Our Company

Special Tools