unittest/discover: Avoid adding test parent dir to sys.path.

When running tests from subfolders, import by "full dotted path" rather than
just module name, removing the need to add the test parent folder to sys.path.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

Author: andrewleech

python-stdlib/unittest-discover/unittest/__main__.py

@@ -14,11 +14,11 @@ def _run_test_module(runner: TestRunner, module_name: str, *extra_paths: list[st
     module_snapshot = {k: v for k, v in sys.modules.items()}
     path_snapshot = sys.path[:]
     try:
-        for path in reversed(extra_paths):
+        for path in extra_paths:
             if path:
                 sys.path.insert(0, path)
 
-        module = __import__(module_name)
+        module = __import__(module_name, None, None, module_name)
         suite = TestSuite(module_name)
         suite._load_module(module)
         return runner.run(suite)
@@ -36,16 +36,18 @@ def _run_all_in_dir(runner: TestRunner, path: str, pattern: str, top: str):
     for fname, ftype, *_ in os.ilistdir(path):
         if fname in ("..", "."):
             continue
+        fpath = "/".join((path, fname))
         if ftype == _DIR_TYPE:
             result += _run_all_in_dir(
                 runner=runner,
-                path="/".join((path, fname)),
+                path=fpath,
                 pattern=pattern,
                 top=top,
             )
         if fnmatch(fname, pattern):
-            module_name = fname.rsplit(".", 1)[0]
-            result += _run_test_module(runner, module_name, path, top)
+            module_path = fpath.rsplit(".", 1)[0]  # remove ext
+            module_path = module_path.replace("/", ".").strip(".")
+            result += _run_test_module(runner, module_path, top)
     return result