pycoder2000/Pytest

COMMANDS

Pytest identifies files whose names start with test_ or ending with _test as the test files.

Pytest identifies functions whose names are starting with test as test functions.

Normal Command Test
```
py.test
pytest
```
Verbose Command Test (To understand the failed tests better)
```
pytest -v agg_test.py
```
To print log messages to console
```
pytest -sv
```
Run multiple tests
```
pytest -v
```
Test with substring
```
pytest -k 'fun' -v test_demo_2.py
```

Test with multiple substring

pytest -k 'fun or sum' -v
pytest -k 'fun and sum' -v
pytest -k 'not fun' -v

Test with Markers
```
import pytest

@pytest.mark.demo
def func():
    pass
```
```
pytest -m 'fun' -v
```
NOTE:
- Both Markers and Substrings are used to run group selective tests.
- If we are willing to change the name of the tests then we can use -k <substring>.
- If not then we can use markers as -m.
Test with Fixtures
```
import pytest

@pytest.fixture(scope="function")
def func():
    i =20
    return i
```
```
pytest -k 'sum' -v test_demo_fixtures.py
```
Fixture Scope
- function: the default scope, the fixture is destroyed at the end of the test.
- class: the fixture is destroyed during teardown of the last test in the class.
- module: the fixture is destroyed during teardown of the last test in the module.
- package: the fixture is destroyed during teardown of the last test in the package.
- session: the fixture is destroyed at the end of the test session.
Also we can autouse = True if we want to run the fixture before every test.
NOTE:
- Fixture has scope only within a test file where it is defined.
- To make a fixture available to multiple test files, we have to define the fixture function in a file called conftest.py
- Pytest will look for the fixture function in the test file and if not found it will look in the conftest.py file.

Test with Parametrize

import pytest

@pytest.mark.parametrize("input, expected",[(1,2),(3,4)])
def func(input,expected):
    assert input + 1 == expected

pytest -k 'sum' -v test_demo_fixtures.py

Skip Tests

import pytest

@pytest.mark.skip("This is a reason for skipping the test")
def func():
    pass

We can also provide conditions to skip the test.

@pytest.mark.skipif(condition,reason = "This is a reason for skipping the test")

pytest -sv

xfail Tests
```
import pytest

@pytest.mark.xfail
def func():
    pass
```
```
pytest -sv
```
NOTE:
- There are used in cases where the test cases are not relevant for a specific period of time.
- The xfail tests will be executed, but will not counted as failed or passed tests.
Stopping file after n fails

If N number of test fails then pytest stops the execution
```
pytest test_demo_2.py -v --maxfail 3
```
Running pytest in parallel
```
pip install pytest-xdist
```
To run the tests in parallel
```
pytest -n 2
```
Here -n specifices the number of workers to run the tests.

To view the logs add sys.stdout = sys.stderr at the top of the file.
Save pytest results To get results in XML format, we have to use
```
pytest --junitxml="results.xml"
```
To get results in HTML format, we have to use
```
pip install pytest-html
pytest --html="results.html"
```