1 files changed, 85 insertions, 0 deletions
diff --git a/tests/test_goldtest.py b/tests/test_goldtest.py
new file mode 100644
index 00000000..fcd41579
--- /dev/null
+++ b/tests/test_goldtest.py
@@ -0,0 +1,85 @@
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
+
+"""Tests of the helpers in goldtest.py"""
+
+import os.path
+import re
+
+import pytest
+
+from tests.coveragetest import CoverageTest, TESTS_DIR
+from tests.goldtest import compare, gold_path
+from tests.helpers import os_sep, re_line, remove_tree
+
+GOOD_GETTY = """\
+Four score and seven years ago our fathers brought forth upon this continent, a
+new nation, conceived in Liberty, and dedicated to the proposition that all men
+are created equal.
+11/19/9999, Gettysburg, Pennsylvania
+"""
+
+BAD_GETTY = """\
+Five score and seven years ago our fathers brought forth upon this continent, a
+new nation, conceived in Liberty, and dedicated to the proposition that all men
+are created equal.
+333/4444/55555, Gettysburg, Pennsylvania
+"""
+
+SCRUBS = [
+    # Numbers don't matter when comparing.
+    (r'\d+', 'D'),
+]
+
+ACTUAL_DIR = os.path.join(TESTS_DIR, "actual/testing")
+ACTUAL_GETTY_FILE = os.path.join(ACTUAL_DIR, "gettysburg.txt")
+
+GOLD_PATH_RE = re.escape(os_sep("/tests/gold/testing/gettysburg.txt"))
+OUT_PATH_RE = re.escape(os_sep("out/gettysburg.txt"))
+
+class CompareTest(CoverageTest):
+    """Tests of goldtest.py:compare()"""
+
+    def setup_test(self):
+        super().setup_test()
+        self.addCleanup(remove_tree, ACTUAL_DIR)
+
+    def test_compare_good(self):
+        self.make_file("out/gettysburg.txt", GOOD_GETTY)
+        compare(gold_path("testing"), "out", scrubs=SCRUBS)
+        self.assert_doesnt_exist(ACTUAL_GETTY_FILE)
+
+    def test_compare_bad(self):
+        self.make_file("out/gettysburg.txt", BAD_GETTY)
+
+        # compare() raises an assertion.
+        msg = rf"Files differ: .*{GOLD_PATH_RE} != {OUT_PATH_RE}"
+        with pytest.raises(AssertionError, match=msg):
+            compare(gold_path("testing"), "out", scrubs=SCRUBS)
+
+        # Stdout has a description of the diff.  The diff shows the scrubbed content.
+        stdout = self.stdout()
+        print(stdout)
+        assert "- Four score" in stdout
+        assert "+ Five score" in stdout
+        assert re_line(stdout, rf"^:::: diff '.*{GOLD_PATH_RE}' and '{OUT_PATH_RE}'")
+        assert re_line(stdout, rf"^:::: end diff '.*{GOLD_PATH_RE}' and '{OUT_PATH_RE}'")
+        assert "  D/D/D, Gettysburg, Pennsylvania" in stdout
+
+        # The actual file was saved.
+        with open(ACTUAL_GETTY_FILE) as f:
+            saved = f.read()
+        assert saved == BAD_GETTY
+
+    def test_compare_good_needs_scrubs(self):
+        # Comparing the "good" result without scrubbing the variable parts will fail.
+        self.make_file("out/gettysburg.txt", GOOD_GETTY)
+
+        # compare() raises an assertion.
+        msg = rf"Files differ: .*{GOLD_PATH_RE} != {OUT_PATH_RE}"
+        with pytest.raises(AssertionError, match=msg):
+            compare(gold_path("testing"), "out")
+
+        stdout = self.stdout()
+        assert "- 11/19/1863, Gettysburg, Pennsylvania" in stdout
+        assert "+ 11/19/9999, Gettysburg, Pennsylvania" in stdout