Add a multi-language mutation tester that writes .metrics/mutate for uml-viewer.

tests/test_cli.py

@@ -0,0 +1,94 @@
+import subprocess
+import sys
+
+from mutator.cli import parse_args, run
+from mutator.runner import CommandResult
+
+
+def test_lines_option_parses_positive_numbers():
+    options = parse_args(["--lines", "2, 4", "src/demo.py"])
+    assert options.lines == {2, 4}
+
+
+def test_changed_selects_a_dirty_source_file(tmp_path, monkeypatch, capsys):
+    path = tmp_path / "src" / "demo.py"
+    path.parent.mkdir()
+    path.write_text("def place(x):\n    return x > 0\n", encoding="utf-8")
+    subprocess.run(["git", "init"], cwd=tmp_path, check=True, capture_output=True)
+    subprocess.run(["git", "add", "src/demo.py"], cwd=tmp_path, check=True, capture_output=True)
+    monkeypatch.chdir(tmp_path)
+    code = run(["--scan", "--no-coverage", "--changed", "--root", str(tmp_path)])
+    captured = capsys.readouterr()
+    assert code == 0
+    assert "demo.py:2" in captured.out
+
+
+def test_a_directory_argument_skips_a_named_test_file(tmp_path, capsys):
+    src = tmp_path / "pkg" / "app.py"
+    src.parent.mkdir()
+    src.write_text("def place(x):\n    return x > 0\n", encoding="utf-8")
+    test = tmp_path / "pkg" / "test_app.py"
+    test.write_text("def test_place():\n    assert True\n", encoding="utf-8")
+    code = run(
+        ["--scan", "--no-coverage", "--root", str(tmp_path), str(tmp_path / "pkg"), str(test)]
+    )
+    captured = capsys.readouterr()
+    assert code == 0
+    assert "Skipping test file" in captured.err
+    assert "app.py:2" in captured.out
+
+
+def test_help_and_conflicting_flags():
+    help_options = parse_args(["--help"])
+    assert help_options.exit_code == 0
+    assert "uml-viewer" in help_options.message
+    conflict = parse_args(["--mutate-all", "--since-last-run", "src/demo.py"])
+    assert conflict.exit_code == 1
+    assert run(["--help"]) == 0
+
+
+def test_scan_lists_sites_without_writing_metrics(tmp_path, monkeypatch):
+    path = tmp_path / "src" / "demo.py"
+    path.parent.mkdir()
+    path.write_text("def place(x):\n    return x > 0\n", encoding="utf-8")
+    monkeypatch.chdir(tmp_path)
+    code = run(["--scan", "--no-coverage", "--root", str(tmp_path), "src/demo.py"])
+    assert code == 0
+    assert not (tmp_path / ".metrics").exists()
+
+
+def test_real_python_mutants_update_the_snapshot(tmp_path, capsys):
+    path = tmp_path / "src" / "demo.py"
+    path.parent.mkdir()
+    path.write_text(
+        "def add(a, b):\n"
+        "    if a > 0:\n"
+        "        return a + b\n"
+        "    return 0\n",
+        encoding="utf-8",
+    )
+    command = (
+        f"{sys.executable} -c \"import sys; sys.path.insert(0, 'src'); "
+        "from demo import add; raise SystemExit(0 if add(2, 3) == 5 else 1)\""
+    )
+    code = run(
+        [
+            "--no-coverage",
+            "--mutate-all",
+            "--root",
+            str(tmp_path),
+            "--test-command",
+            command,
+            "src/demo.py",
+        ]
+    )
+    captured = capsys.readouterr()
+    assert code == 3
+    assert "SURVIVED" in captured.out
+    assert "KILLED" in captured.out
+    snapshot = tmp_path / ".metrics" / "mutate" / "demo.edn"
+    assert snapshot.is_file()
+    text = snapshot.read_text(encoding="utf-8")
+    assert ":namespace \"demo\"" in text
+    assert ":id \"defn/add\"" in text
+    assert path.read_text(encoding="utf-8").startswith("def add")