Changing Test Discovery Rules
pytest finds tests to run based on certain test discovery rules. The standard test discovery rules are:
-
Start at one or more directory. You can specify filenames or directory names on the command line. If you don’t specify anything, the current directory is used.
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Look in the directory and all subdirectories recursively for test modules.
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A test module is a file with a name that looks like test_*.py or *_test.py.
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Look in test modules for functions that start with test_.
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Look for classes that start with Test. Look for methods in those classes that start with test_ but don’t have an __init__ method.
These are the standard discovery rules; however, you can change them.
python_classes
The usual test discovery rule for pytest and classes is to consider a class a potential test class if it starts with Test*. The class also can’t have an __init__() function. But what if we want to name our test classes <something>Test or <something>Suite? That’s where python_classes comes in:
| | [pytest] |
| | python_classes = *Test Test* *Suite |
This enables us to name classes like this:
| | class DeleteSuite(): |
| | def test_delete_1(): |
| | ... |
| | |
| | def test_delete_2(): |
| | ... |
| | |
| | .... |
python_files
Like pytest_classes, python_files modifies the default test discovery rule, which is to look for files that start with test_* or end in *_test.
Let’s say you have a custom test framework in which you named all of your test files check_<something>.py. Seems reasonable. Instead of renaming all of your files, just add a line to pytest.ini like this:
| | [pytest] |
| | python_files = test_* *_test check_* |
Easy peasy. Now you can migrate your naming convention gradually if you want to, or just leave it as check_*.
python_functions
python_functions acts like the previous two settings, but for test function and method names. The default is test_*. To add check_*—you guessed it—do this:
| | [pytest] |
| | python_functions = test_* check_* |
Now the pytest naming conventions don’t seem that restrictive, do they? If you don’t like the default naming convention, just change it. However, I encourage you to have a better reason. Migrating hundreds of test files is definitely a good reason.