The command "pip install -e '.[docs,test]'" from the installation section in README.md maybe should be written as "pip install -e '.[docs,tests]'",because the corresponding file name in the project is "tests",or rename the "tests" to "test".
The test in the command does not refer to the "tests" directory, but to the test-variable in the [project.optional-dependencies]-section of the pyproject.toml-file. But thanks for the hint.
The command "pip install -e '.[docs,test]'" from the installation section in README.md maybe should be written as "pip install -e '.[docs,tests]'",because the corresponding file name in the project is "tests",or rename the "tests" to "test".