Run slow tests without coverage

Per suggestion from @alexmojaki at
#129 (comment)

These slower tests are integration/kitchen-sink tests, so they
shouldn't add substantially to the code coverage. Running them
without coverage is quite a lot faster (several minutes in CI)
which is well worth the small additional complexity.

This commit also drops pytest outputting the junit xml file
as there's not an obvious way to combine that from multiple
test runs and it appears to be unused.

.github/workflows/build-and-test.yml

@@ -83,9 +83,11 @@ jobs:
 
       - name: Test with pytest
         run: |
-          pytest --cov -n auto --junitxml=./rspec.xml
+          pytest --cov -n auto -m "not slow"
           coverage report -m
 
+          pytest -n auto -m slow
+
       - name: Collect coverage results
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

setup.cfg

@@ -61,4 +61,6 @@ universal=1
 
 
 [tool:pytest]
-addopts = --disable-warnings --ignore=tests/testdata
+addopts = --disable-warnings --ignore=tests/testdata --strict-markers
+markers =
+  slow: marks tests as slow (deselect with '-m "not slow"')

tests/test_mark_tokens.py

@@ -5,6 +5,7 @@
 import inspect
 import io
 import os
+import pytest
 import re
 import sys
 import textwrap
@@ -630,6 +631,7 @@ def test_complex_slice_and_parens(self):
     self.create_mark_checker(source)
 
   if six.PY3:
+    @pytest.mark.slow
     def test_sys_modules(self):
       """
       Verify all nodes on source files obtained from sys.modules.