Fixed failure of exit-behavior tests during coverage reporting.

Just like in the recently revamped test runner (`test.py`), the project
root folder must be added to the Python search path. While pyTest does
add the root folder to `sys.path` in its own process, it is not available
in the subprocesses testing the exit behavior. Which is why these tests
failed when `tools/coverage.py` was run.

tools/codecov.py

@@ -1,12 +1,24 @@
-"""Uploads the coverage report to CodeCov."""
+"""
+Uploads the coverage report to CodeCov.
+
+The script expects the CodeCov uploader to be installed locally. On
+Windows, for example, `codecov.exe` would have to be on the search path.
+It also expects the CodeCov upload token for this project to be set as
+an environment variable.
+
+CodeCov does not accept Coverage.py's standard report format, i.e. the
+`.coverage` file. It must be converted to XML format before upload.
+"""
 
 from subprocess import run
 from pathlib import Path
 from os import environ
 
+
 token = environ.get('MPh_CodeCov_token', None)
 if not token:
     raise RuntimeError('CodeCov upload token not set in environment.')
 
 root = Path(__file__).resolve().parent.parent
+run(['coverage', 'xml'], cwd=root)
 run(['codecov', '--file', 'coverage.xml', '--token', token], cwd=root)

tools/coverage.py

@@ -5,32 +5,46 @@
 of the repo) because the individual scripts there all start a client in
 their respective setup routine. That is, they all start the Java VM,
 which will fail once pyTest gets to the second script in the sequence.
-Instead, we run pyTest for each script separately, with the coverage
-plug-in enabled, and generate the coverage report incrementally.
+Instead, we run pyTest for each test group separately, with the coverage
+plug-in enabled, and thus generate the coverage report incrementally.
 
-If the coverage report file (`coverage.xml`) already exists, we instead
-render it as HTML for inspection. This is helpful during development.
-The coverage report may also be uploaded to an online service such as
-CodeCov for each published release or even commit, see `codecov.py`.
+We also render the coverage report (in `.coverage`) as HTML for easy
+inspection. This is helpful during development.
+
+The coverage report may be uploaded to the online service CodeCov. This is
+usually only done for a new release, but could also happen on each commit.
+There's a separate script, `codecov.py`, to automate that.
 """
 
 from subprocess import run
-from pathlib import Path
-import sys
-
-tests = ['meta', 'config', 'discovery', 'server', 'session', 'standalone',
-         'client', 'multi', 'node', 'model', 'exit']
-
-here   = Path(__file__).resolve().parent
-root   = here.parent
-file   = root/'coverage.xml'
-python = sys.executable
-if not file.exists():
-    command = [python, '-m', 'pytest',
-               '--cov', '--cov-append', '--cov-report', 'xml']
-    for test in tests:
-        run(command + [f'tests/test_{test}.py'], cwd=root)
+from pathlib    import Path
+from sys        import executable as python
+from os         import environ, pathsep
+
+
+# Define order of test groups.
+groups = ['meta', 'config', 'discovery', 'server', 'session', 'standalone',
+          'client', 'multi', 'node', 'model', 'exit']
+
+# Determine path of project root folder.
+here = Path(__file__).resolve().parent
+root = here.parent
+
+# Run MPh in project folder, not a possibly different installed version.
+if 'PYTHONPATH' in environ:
+    environ['PYTHONPATH'] = str(root) + pathsep + environ['PYTHONPATH']
 else:
-    print('Rendering existing coverage report as HTML.')
-    folder = (here/'coverage').relative_to(root)
-    run(['coverage', 'html', f'--directory={folder}'], cwd=root)
+    environ['PYTHONPATH'] = str(root)
+
+# Report code coverage one by one for each test group.
+report = root/'.coverage'
+if report.exists():
+    report.unlink()
+for group in groups:
+    run([python, '-m', 'pytest', '--cov', '--cov-append',
+         f'tests/test_{group}.py'], cwd=root)
+
+# Render coverage report locally.
+print('Exporting coverage report as HTML.')
+folder = (here/'coverage').relative_to(root)
+run(['coverage', 'html', f'--directory={folder}'], cwd=root)