Coding style.

- golden.py is used by the tests, not vigil.

tests/__main___test.py

@@ -13,8 +13,8 @@ import unittest
 
 os.environ["TERM"] = "xterm-256color"
 
+import golden
 import vigil.fill3 as fill3
-import vigil.golden as golden
 import vigil.__main__ as __main__
 
 

tests/golden.py

@@ -0,0 +1,78 @@
+
+# Copyright (C) 2015-2017 Andrew Hamilton. All rights reserved.
+# Licensed under the Artistic License 2.0.
+
+import optparse
+import os.path
+import shutil
+import subprocess
+import sys
+import tempfile
+import unittest
+
+
+def _accept_actual(failed):
+    for actual_str, golden_path in failed:
+        with open(golden_path, "w") as golden_file:
+            golden_file.write(actual_str)
+        print("Wrote golden file: %s" % golden_path)
+
+
+def _run_meld_gui(failed):
+    temp_dir = tempfile.mkdtemp()
+    try:
+        golden_dir = os.path.join(temp_dir, "golden")
+        actual_dir = os.path.join(temp_dir, "actual")
+        os.mkdir(golden_dir)
+        os.mkdir(actual_dir)
+        for actual_str, golden_file in failed:
+            name = os.path.basename(golden_file)
+            actual_path = os.path.join(actual_dir, name)
+            with open(actual_path, "w") as actual:
+                actual.write(actual_str)
+            os.symlink(os.path.abspath(golden_file),
+                       os.path.join(golden_dir, name))
+        subprocess.call(["meld", actual_dir, golden_dir])
+    finally:
+        shutil.rmtree(temp_dir)
+
+
+_FAILED = set()
+
+
+def assertGolden(actual, golden_path):
+    try:
+        with open(golden_path, "r") as golden_file:
+            expected = golden_file.read()
+    except FileNotFoundError:
+        expected = None
+    if actual != expected:
+        _FAILED.add((actual, golden_path))
+        if expected is None:
+            raise unittest.TestCase.failureException(
+                'The golden file does not exist: %r\nUse "--diff" or'
+                ' "--accept" to create the golden file.' % golden_path)
+        else:
+            raise unittest.TestCase.failureException(
+                'Output does not match golden file: %r\nUse "--diff" or'
+                ' "--accept" to update the golden file.' % golden_path)
+
+
+def main():
+    parser = optparse.OptionParser()
+    parser.add_option("-a", "--accept", action="store_true",
+                      dest="should_accept_actual")
+    parser.add_option("-d", "--diff", action="store_true", dest="should_diff")
+    options, args = parser.parse_args()
+    # unitest.main doesn't expect these arguments, so remove them.
+    for argument in ["-a", "--accept", "-d", "--diff"]:
+        if argument in sys.argv:
+            sys.argv.remove(argument)
+    try:
+        unittest.main()
+    finally:
+        if len(_FAILED) > 0:
+            if options.should_accept_actual:
+                _accept_actual(_FAILED)
+            if options.should_diff:
+                _run_meld_gui(_FAILED)