Writing unit tests

Satpy tests are written using the third-party pytest package.


The usage of Pytest fixtures is encouraged for code re-usability.

As the builtin fixtures (and those defined in conftest.py file) are injected by Pytest without them being imported explicitly, their usage can be very confusing for new developers. To lessen the confusion, it is encouraged to add a note at the top of the test modules listing all the automatically injected external fixtures that are used in the module:

# The following fixtures are not defined in this file, but are used and injected by Pytest:
# - tmp_path
# - fixture_defined_in_conftest.py