Use underscore for system test names

Change the convention for system test directory names to always use an
underscore rather than a hyphen. Names using underscore are valid python
package names and can be used with standard `import` facilities in
python, which allows easier code reuse.

The temporary directories for test execution and their convenience
symlinks have been switched to using hyphens rather than underscores to
keep the pytest collection, filtering and .gitignore working as
expected.

bin/tests/system/.gitignore

@@ -25,10 +25,8 @@ named.run
 !/isctest/vars/.build_vars/*.in
 !/isctest/vars/.build_vars/meson.build
 
-# Ignore file names with underscore in their name except python or shell files.
+# Ignore file names with a hyphen in their name except C files.
 # This is done to ignore the temporary directories and symlinks created by the
 # pytest runner, which contain underscore in their file names.
-/*_*
-!/*_*.py
-!/*_*.sh
-!/_common
+/*-*
+!/*-*.c

bin/tests/system/README.md

@@ -123,15 +123,12 @@ Each test module is executed inside a unique temporary directory which contains
 all the artifacts from the test run. If the tests succeed, they are deleted by
 default. To override this behaviour, pass `--noclean` to pytest.
 
-The directory name starts with the system test name, followed by `_tmp_XXXXXX`,
-i.e. `dns64_tmp_r07vei9s` for `dns64` test run. Since this name changes each
+The directory name starts with the system test name, followed by `-tmp-XXXXXX`,
+i.e. `dns64-tmp-r07vei9s` for `dns64` test run. Since this name changes each
 run, a convenience symlink that has a stable name is also created. It points to
-the latest test artifacts directory and has a form of `dns64_sh_dns64`
+the latest test artifacts directory and has a form of `dns64-sh_dns64`
 (depending on the particular test module).
 
-To clean up the temporary directories and symlinks, run `make clean-local` in
-the system test directory.
-
 The following test artifacts are typically available:
 
 - pytest.log.txt: main log file with test output

bin/tests/system/conftest.py

@@ -54,7 +54,7 @@ PRIORITY_TESTS = [
 ]
 PRIORITY_TESTS_RE = Re("|".join(PRIORITY_TESTS))
 SYSTEM_TEST_NAME_RE = Re(f"{SYSTEM_TEST_DIR_GIT_PATH}" + r"/([^/]+)")
-SYMLINK_REPLACEMENT_RE = Re(r"/tests(_.*)\.py")
+SYMLINK_REPLACEMENT_RE = Re(r"/tests_(.*)\.py")
 
 # ----------------------- Global requirements ----------------------------
 
@@ -84,14 +84,14 @@ def pytest_ignore_collect(collection_path):
     # ignore these during test collection phase. Otherwise, test artifacts
     # from previous runs could mess with the runner. Also ignore the
     # convenience symlinks to those test directories. In both of those
-    # cases, the system test name (directory) contains an underscore, which
+    # cases, the system test name (directory) contains a hyphen, which
     # is otherwise and invalid character for a system test name.
     match = SYSTEM_TEST_NAME_RE.search(str(collection_path))
     if match is None:
         isctest.log.warning("unexpected test path: %s (ignored)", collection_path)
         return True
     system_test_name = match.groups()[0]
-    return "_" in system_test_name
+    return "-" in system_test_name
 
 
 def pytest_collection_modifyitems(items):
@@ -385,14 +385,14 @@ def system_test_dir(request, system_test_name, expected_artifacts):
     # Create a temporary directory with a copy of the original system test dir contents
     system_test_root = Path(os.environ["srcdir"]).resolve()
     testdir = Path(
-        tempfile.mkdtemp(prefix=f"{system_test_name}_tmp_", dir=system_test_root)
+        tempfile.mkdtemp(prefix=f"{system_test_name}-tmp-", dir=system_test_root)
     )
     shutil.rmtree(testdir)
     shutil.copytree(system_test_root / system_test_name, testdir)
     isctest.vars.dirs.set_system_test_name(testdir.name)
 
     # Create a convenience symlink with a stable and predictable name
-    module_name = SYMLINK_REPLACEMENT_RE.sub(r"\1", str(request.node.path))
+    module_name = SYMLINK_REPLACEMENT_RE.sub(r"-\1", str(request.node.path))
     symlink_dst = system_test_root / module_name
     symlink_dst.unlink(missing_ok=True)
     symlink_dst.symlink_to(os.path.relpath(testdir, start=system_test_root))

dangerfile.py

@@ -483,10 +483,10 @@ for testname in testnames:
         or testname == "isctest"
     ):
         continue
-    if "_" in testname:
+    if "-" in testname:
         fail(
-            f"System test directory `{testname}` may not contain an underscore, "
-            "use hyphen instead."
+            f"System test directory `{testname}` may not contain a hyphen, "
+            "use underscore instead."
         )
     if not glob.glob(f"{dirpath}/**/tests_*.py", recursive=True):
         fail(