Move tests_require to special "tests" extra for easier installation

doc/source/dev_guide/index.rst

@@ -61,20 +61,33 @@ clone your fork. The package can then be installed in development mode by doing:
 The first command will install all dependencies needed by the Satpy
 conda-forge package, but won't actually install Satpy. The second command
 should be run from the root of the cloned Satpy repository (where the
-`setup.py` is) and will install the actual package.
+``setup.py`` is) and will install the actual package.
 
 You can now edit the python files in your cloned repository and have them
 immediately reflected in your conda environment.
 
 Running tests
 =============
 
-Satpy tests are written using the python :mod:`unittest` module and the
-third-party :doc:`pytest <pytest:index>` package. Satpy tests can be executed by
-running::
+Satpy tests are written using the third-party :doc:`pytest <pytest:index>`
+package. There is usually no need to run all Satpy tests, but instead only
+run the tests related to the component you are working on. All tests are
+automatically run from the GitHub Pull Request using multiple versions of
+Python, multiple operating systems, and multiple versions of dependency
+libraries. If you want to run all Satpy tests you will need to install
+additional dependencies that aren't needed for regular Satpy usage. To install
+them run::
+
+    pip install -e .[tests]
+
+Satpy tests can be executed by running::
 
     pytest satpy/tests
 
+You can also run a specific tests by specifying a sub-directory or module::
+
+    pytest satpy/tests/reader_tests/test_abi_l1b.py
+
 Running benchmarks
 ==================
 

pyproject.toml

@@ -1,5 +1,6 @@
 [build-system]
-requires = ["setuptools>=42", "wheel", "setuptools_scm[toml]>=3.4", 'setuptools_scm_git_archive']
+requires = ["setuptools>=45", "wheel", "setuptools_scm[toml]>=6.2", 'setuptools_scm_git_archive']
+build-backend = "setuptools.build_meta"
 
 [tool.setuptools_scm]
 write_to = "satpy/version.py"

satpy/__init__.py

@@ -18,7 +18,14 @@
 """Satpy Package initializer."""
 
 import os
-from satpy.version import version as __version__  # noqa
+
+try:
+    from satpy.version import version as __version__  # noqa
+except ModuleNotFoundError:
+    raise ModuleNotFoundError(
+        "No module named satpy.version. This could mean "
+        "you didn't install 'satpy' properly. Try reinstalling ('pip "
+        "install').")
 
 CHUNK_SIZE = int(os.getenv('PYTROLL_CHUNK_SIZE', 4096))
 

setup.py

@@ -79,6 +79,7 @@
     # Other
     'geoviews': ['geoviews'],
     'overlays': ['pycoast', 'pydecorate'],
+    'tests': test_requires,
 }
 all_extras = []
 for extra_deps in extras_require.values():
@@ -154,7 +155,6 @@ def _config_data_files(base_dirs, extensions=(".cfg", )):
       use_scm_version={'write_to': 'satpy/version.py'},
       setup_requires=['setuptools_scm', 'setuptools_scm_git_archive'],
       install_requires=requires,
-      tests_require=test_requires,
       python_requires='>=3.7',
       extras_require=extras_require,
       entry_points=entry_points,