How to Run pytest: Simple Commands and Examples

To run tests with pytest, open your terminal and type pytest in the directory containing your test files. You can also specify a test file or folder like pytest test_example.py to run specific tests.

Syntax

The basic command to run pytest is pytest. You can add options or specify files/folders:

• pytest: Runs all tests in the current directory and subdirectories.
• pytest test_file.py: Runs tests in a specific file.
• pytest -v: Runs tests with detailed output.
• pytest -k 'expression': Runs tests matching the expression.

bash

pytest [options] [file_or_dir]

Example

This example shows a simple test file and how to run it with pytest.

python

def test_addition():
    assert 2 + 3 == 5

def test_subtraction():
    assert 5 - 2 == 3

Output

============================= test session starts ==============================
collected 2 items

test_example.py ..                                                         [100%]

============================== 2 passed in 0.01s ===============================

Common Pitfalls

Common mistakes when running pytest include:

• Running pytest in the wrong directory where tests are not found.
• Not naming test files or functions correctly (they must start with test_).
• Using incorrect command syntax or missing the -v option for detailed output.

python

## Wrong: test file named example.py (no 'test_' prefix)
# pytest will not find tests here

def test_sample():
    assert True


## Right: test file named test_example.py
# pytest will discover this file and run tests

def test_sample():
    assert True

Quick Reference

Command	Description
pytest	Run all tests in current directory and subdirectories
pytest test_file.py	Run tests in a specific file
pytest -v	Run tests with detailed output
pytest -k 'expr'	Run tests matching expression
pytest --maxfail=1	Stop after first failure

Key Takeaways

Run pytest by typing pytest in the terminal inside your test folder.

Test files and functions must start with test_ for pytest to find them.

Use pytest -v for more detailed test results.

Specify test files or folders to run specific tests.

Check your current directory if pytest does not find any tests.