How to Run A Test Using Pytest?

To run a test using pytest, you first need to write your test functions using the pytest framework. These functions should begin with the "test_" prefix.

Next, you need to save your test file with a ".py" extension. You can organize your test files in a separate directory within your project.

To run the test, open a terminal or command prompt, navigate to the directory where your test file is located, and type "pytest" followed by the name of your test file.

Pytest will automatically discover and run all the test functions in your file, displaying the results in the terminal. You will see a summary of passed and failed tests, along with any error messages if a test fails.

You can also use various command-line options with pytest to customize the test execution, such as running specific tests, generating reports, or setting configurations. Refer to the pytest documentation for more information on how to use these options.

How to specify test parameters in pytest?

In pytest, you can specify test parameters using pytest.mark.parametrize decorator.

Here's an example:

1
2
3
4
5
6
7
8
9

import pytest

@pytest.mark.parametrize("input_value, expected_output", [
    (1, 2),
    (2, 4),
    (3, 6),
])
def test_multiply_by_2(input_value, expected_output):
    assert input_value * 2 == expected_output

In this example, the test_multiply_by_2 test function takes two parameters input_value and expected_output. The pytest.mark.parametrize decorator is used to provide multiple sets of input values and expected output values for the test function to run against. The test will be executed for each set of parameters provided in the list.

What is the purpose of pytest fixtures?

Pytest fixtures are used to provide a reusable piece of setup and teardown code for tests. They allow you to define common setup steps that are needed for multiple tests in a modular way, making it easier to maintain and reuse code. Fixtures can be used to create objects, initialize databases, set up configurations, and perform other setup tasks before running tests. They help in reducing code duplication and making tests easier to read and maintain.

How to perform teardown after running tests in pytest?

Teardown in pytest can be performed using fixtures. Fixtures are reusable objects that can be set up before running tests and torn down after the tests have been executed. To perform teardown after running tests in pytest, you can define a fixture with a teardown function using the yield statement.

Here is an example of how to define and use a fixture for teardown in pytest:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20

import pytest

# Define a fixture with teardown function
@pytest.fixture
def teardown_fixture():
    # Setup
    print("Setting up before running tests")
    
    yield
    
    # Teardown
    print("Tearing down after running tests")

# Test function that uses the teardown fixture
def test_example(teardown_fixture):
    assert True
    
# Run tests
if __name__ == '__main__':
    pytest.main([__file__])

In this example, the teardown_fixture fixture is defined with a setup function that prints a message before running tests and a teardown function that prints a message after running tests. The yield statement is used to indicate where the teardown should happen.

When the test_example test function is run, the teardown_fixture fixture will be invoked before and after the test, allowing you to perform any necessary teardown actions.