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pytest usage Cheat Sheet by

A cheatsheet for using pytest

Instal­lation

pip install pytest

Running pytest

pytest test_m­od.py
Run tests in module
pytest testing/
Run multiple modules
pytest test_m­­od.p­­y:­­:te­­st­_func
Run a specific test within a module.
pytest test_m­­od.p­­y:­­:Te­­st­C­l­as­­s::­­te­s­t­_m­­ethod
Run a specific method of a class.

Assertions

pytest allows you to use the standard Python assert for verifying expect­ations and values in Python tests. For example, you can write the following:
 
assert a % 2 == 0
assert that you have a certain value.
 
assert a % 2 == 0,
"value was odd, should be even"
specify a message with the assertion like this

Grouping in tests

@pytest.mark.<markername>
mark it in tests
pytest tests/ -m "­san­ity­tes­ts"
run using -m flag

Disable tests

@pytest.mark.skip(
    reason­="no way of currently testing this")

Assertion of expected exceptions

Test if the exception is raised
 
def test_zero_division():
  with pytest.raises(ZeroDivisionError):
    1 / 0
Test for specific exception info
 
def test_recursion_depth():
  with pytest.ra­ise­s(R­unt­ime­Error) as excinfo:
    assert "­max­imu­m" in str(ex­cin­fo.v­alue)

MultiT­hre­ading

pip install pytest-xdist
 pytest tests/ -n 3
Pytest does not run in parallel by default, therefor we need to enable this behaviour through a plugin.
 

Fixtures

In testing, a fixture provides a defined, reliable and consistent context for the tests. This could include enviro­nment (for example a database configured with known parame­ters) or content (such as a dataset).
 
@pytest.fixture
 def input_value():
    input = 10
    return input
Create fixture in conftest
 
def test_divisible_by_3(input_value):
    assert input_­value % 3 == 0
Use it in tests
 
@pytest.fixture
 def sending_user(mail_admin):
     user = mail_admin.create_user()
     yield user
     mail_a­dmi­n.d­ele­te_­use­r(user)
using yield to setup and teardown test enviro­nment
@pytest.fixture(scope="function")
Pytest fixtures have scope. This scope controls how often the fixture is executed or, in other words, how often the setup and teardown of the fixture is performed.
@pytest.fixture(scope="module")
@pytest.fixture(scope="class")
@pytest.fixture(scope="session")

Data parame­ter­ization

The builtin pytest.ma­rk.p­ar­ame­trize decorator enables parame­tri­zation of arguments for a test function
Define parame­trized tests
 
@pytes­t.m­ark.pa­ram­etr­ize­("num, output",
 [(1,11),(2,22),(3,35),(4,44)])
def test_m­ult­ipl­ica­tio­n_1­1(num, output):
    assert 11*num == output
Running specific tests of a parame­trized test.
test_m­od.p­y:­:te­st_­mul­tip­lic­ati­on_­11[­2-22]
   
 

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  • Published: 1st June, 2023

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