Add app-level tests and fix fix command

fix command was broken - somehow missed adding @file_options to
it...

src/copyright2/app.py

@@ -189,6 +189,7 @@ def process(file: fs.File) -> None:
 
 @main.command
 @path_options
+@file_options
 def fix(
     find_path_type: PathFinderType,
     find_path_args: Tuple[str, ...],

tests/test_app.py

@@ -0,0 +1,86 @@
+from collections.abc import Iterator
+from contextlib import contextmanager
+from pathlib import Path
+from tempfile import TemporaryDirectory
+from shutil import copytree
+
+from click.testing import CliRunner
+from pytest import MonkeyPatch, fixture
+
+from copyright2.app import list, check, fix
+
+
+__DIR__ = Path(__file__).parent
+
+
+EXAMPLES = __DIR__.parent / "examples"
+
+
+@contextmanager
+def clone_example(monkeypatch: MonkeyPatch, name: str) -> Iterator[None]:
+    with TemporaryDirectory() as _dir:
+        dir = Path(_dir)
+        copytree(EXAMPLES / name, dir / name)
+        monkeypatch.chdir(dir / name)
+        yield
+
+
+@fixture
+def examples_readme(monkeypatch: MonkeyPatch) -> Iterator[None]:
+    with clone_example(monkeypatch, "readme"):
+        yield
+
+
+@fixture
+def examples_subdirs(monkeypatch: MonkeyPatch) -> Iterator[None]:
+    with clone_example(monkeypatch, "subdirs"):
+        yield
+
+
+def test_list_readme(examples_readme: None) -> None:
+    result = CliRunner().invoke(list)
+
+    assert result.exit_code == 0
+
+    assert result.stdout.splitlines() == [
+        "README.md",
+        "src/readme.py",
+        "src/ext/readme.h",
+        "src/ext/readme.c",
+        "4",
+    ]
+
+
+def test_check_readme(examples_readme: None) -> None:
+    result = CliRunner().invoke(check)
+
+    assert result.exit_code != 0
+
+    assert result.stdout.splitlines() == [
+        "README.md: notice not found",
+        "src/ext/readme.h: 2: simplified timestamp expression",
+        "2",
+    ]
+
+
+def test_fix_readme(examples_readme: None) -> None:
+    result = CliRunner().invoke(fix)
+
+    assert result.exit_code != 0
+
+    assert result.stdout.splitlines() == [
+        "README.md: notice not found",
+        "fixing src/ext/readme.h... ok",
+        "1",
+    ]
+
+
+def test_list_subdirs(examples_subdirs: None) -> None:
+    result = CliRunner().invoke(list)
+
+    assert result.exit_code == 0
+
+    assert result.stdout.splitlines() == [
+        "a/b/included.py",
+        "1",
+    ]