Add pytest-cov, requirements-dev, pyproject.toml

When tests finish, a report should be printed that shows the code
coverage of timm. This should give us a better idea where we should work
on test coverage.

I have tested this locally (on a subset of tests) and it worked.

Since the number of test dependencies was getting quite high, I created
a requirements-dev.txt and moved them there. GH action and
CONTRIBUTING.md are adjusted accordingly.

Furthermore, instead of extending the pytest invocation, I created a
pyproject.toml and added the coverage options there. For completeness, I
also added the black settings that come closest to the style of timm.
LMK if this is not desired.

For now, the coverage is only reported but not enforced. I.e. when a PR
is created that adds uncovered lines, CI will still succeed. We could
think about adding codecov or something like that, but it can be
annoying sometimes and the service was flaky for me in the past.

.github/workflows/tests.yml

@@ -30,7 +30,7 @@ jobs:
     - name: Install testing dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install pytest pytest-timeout pytest-xdist pytest-forked expecttest
+        pip install -r requirements-dev.txt
     - name: Install torch on mac
       if: startsWith(matrix.os, 'macOS')
       run: pip install --no-cache-dir torch==${{ matrix.torch }} torchvision==${{ matrix.torchvision }}

CONTRIBUTING.md

@@ -73,18 +73,13 @@ There are a LOT of gaps in current documentation relative to the functionality i
 
 # Installation
 
-Create a Python virtual environment using Python 3.10. Inside the environment, install the following test dependencies:
-
-```
-python -m pip install pytest pytest-timeout pytest-xdist pytest-forked expecttest
-```
-
-Install `torch` and `torchvision` using the instructions matching your system as listed on the [PyTorch website](https://pytorch.org/).
+Create a Python virtual environment using Python 3.10. Inside the environment, install torch` and `torchvision` using the instructions matching your system as listed on the [PyTorch website](https://pytorch.org/).
 
 Then install the remaining dependencies:
 
 ```
 python -m pip install -r requirements.txt
+python -m pip install -r requirements-dev.txt  # for testing
 python -m pip install --no-cache-dir git+https://github.com/mapillary/inplace_abn.git
 python -m pip install -e .
 ```

pyproject.toml

@@ -0,0 +1,12 @@
+[tool.pytest.ini_options]
+addopts = "--cov=timm --cov-report=term-missing"
+
+[tool.coverage.run]
+omit = [
+    "tests/test_*.py",
+]
+
+[tool.black]
+line-length = 120
+target-version = ['py37', 'py38', 'py39', 'py310', 'py311']
+skip-string-normalization = true

requirements-dev.txt

@@ -0,0 +1,6 @@
+pytest
+pytest-timeout
+pytest-xdist
+pytest-forked
+expecttest
+pytest-cov