First commit of file-contents-sorter precommit hook

tests/file_contents_sorter_test.py

@@ -0,0 +1,54 @@
+from argparse import ArgumentError
+
+import pytest
+
+from pre_commit_hooks.file_contents_sorter import FAIL
+from pre_commit_hooks.file_contents_sorter import main
+from pre_commit_hooks.file_contents_sorter import parse_commandline_input
+from pre_commit_hooks.file_contents_sorter import PASS
+from pre_commit_hooks.file_contents_sorter import sort_file_contents
+
+
+def _n(*strs):
+    return b'\n'.join(strs) + '\n'
+
+
+# Input, expected return value, expected output
+TESTS = (
+    (b'', PASS, b''),
+    (_n('lonesome'), PASS, _n('lonesome')),
+    (b'missing_newline', PASS, b'missing_newline'),
+    (_n('alpha', 'beta'), PASS, _n('alpha', 'beta')),
+    (_n('beta', 'alpha'), FAIL, _n('alpha', 'beta')),
+    (_n('C', 'c'), PASS, _n('C', 'c')),
+    (_n('c', 'C'), FAIL, _n('C', 'c')),
+    (_n('mag ical ', ' tre vor'), FAIL, _n(' tre vor', 'mag ical ')),
+    (_n('@', '-', '_', '#'), FAIL, _n('#', '-', '@', '_')),
+)
+
+
+@pytest.mark.parametrize(('input_s', 'expected_retval', 'output'), TESTS)
+def test_integration(input_s, expected_retval, output, tmpdir):
+    path = tmpdir.join('file.txt')
+    path.write_binary(input_s)
+
+    output_retval = main([path.strpath])
+
+    assert path.read_binary() == output
+    assert output_retval == expected_retval
+
+
+def test_parse_commandline_input_errors_without_args():
+    with pytest.raises(SystemExit):
+        parse_commandline_input([])
+
+@pytest.mark.parametrize(
+    ('filename_list'), 
+    (
+        ['filename1'], 
+        ['filename1', 'filename2'],
+    )
+)
+def test_parse_commandline_input_success(filename_list):
+    args = parse_commandline_input(filename_list)
+    assert args.filenames == filename_list