Refactor datetime recency testing into a tested test helper

3 files changed, 36 insertions, 8 deletions

diff --git a/tests/coveragetest.py b/tests/coveragetest.py
index 0e80f4a9..1623ef99 100644
--- a/tests/coveragetest.py
+++ b/tests/coveragetest.py
@@ -1,5 +1,6 @@
 """Base test case class for coverage testing."""
 
+import datetime
 import glob
 import os
 import random
@@ -278,6 +279,14 @@ class CoverageTest(
         if not s.startswith(prefix):
             self.fail(msg or ("%r doesn't start with %r" % (s, prefix)))
 
+    def assert_recent_datetime(self, dt, seconds=10, msg=None):
+        """Assert that `dt` marks a time at most `seconds` seconds ago."""
+        age = datetime.datetime.now() - dt
+        # Python2.6 doesn't have total_seconds :(
+        self.assertEqual(age.days, 0, msg)
+        self.assertGreaterEqual(age.seconds, 0, msg)
+        self.assertLessEqual(age.seconds, seconds, msg)
+
     def command_line(self, args, ret=OK, _covpkg=None):
         """Run `args` through the command line.
 
diff --git a/tests/test_html.py b/tests/test_html.py
index 6f0b294a..6f6f42e4 100644
--- a/tests/test_html.py
+++ b/tests/test_html.py
@@ -386,16 +386,13 @@ class HtmlTest(HtmlTestHelpers, CoverageTest):
         m = re.search(timestamp_pat, html)
         self.assertTrue(m, "Didn't find a timestamp!")
         timestamp = datetime.datetime(*map(int, m.groups()))
-        age = datetime.datetime.now() - timestamp
-        # Python2.6 doesn't have total_seconds :(
-        self.assertEqual(age.days, 0)
         # The timestamp only records the minute, so the delta could be from
         # 12:00 to 12:01:59, or two minutes.
-        self.assertLessEqual(
-            abs(age.seconds),
-            120,
-            "Timestamp is wrong: {0}".format(timestamp)
-        )
+        self.assert_recent_datetime(
+            timestamp,
+            seconds=120,
+            msg="Timestamp is wrong: {0}".format(timestamp),
+            )
 
 
 class HtmlStaticFileTest(CoverageTest):
diff --git a/tests/test_testing.py b/tests/test_testing.py
index 75db7e50..08ff257d 100644
--- a/tests/test_testing.py
+++ b/tests/test_testing.py
@@ -1,6 +1,7 @@
 # -*- coding: utf-8 -*-
 """Tests that our test infrastructure is really working!"""
 
+import datetime
 import os
 import sys
 
@@ -80,6 +81,27 @@ class CoverageTestTest(CoverageTest):
         with self.assertRaises(AssertionError):
             self.assert_starts_with("xyz\nabc", "a")
 
+    def test_assert_recent_datetime(self):
+        def now_delta(seconds):
+            """Make a datetime `seconds` seconds from now."""
+            return datetime.datetime.now() + datetime.timedelta(seconds=seconds)
+
+        # Default delta is 10 seconds.
+        self.assert_recent_datetime(now_delta(0))
+        self.assert_recent_datetime(now_delta(-9))
+        with self.assertRaises(AssertionError):
+            self.assert_recent_datetime(now_delta(-11))
+        with self.assertRaises(AssertionError):
+            self.assert_recent_datetime(now_delta(1))
+
+        # Delta is settable.
+        self.assert_recent_datetime(now_delta(0), seconds=120)
+        self.assert_recent_datetime(now_delta(-100), seconds=120)
+        with self.assertRaises(AssertionError):
+            self.assert_recent_datetime(now_delta(-1000), seconds=120)
+        with self.assertRaises(AssertionError):
+            self.assert_recent_datetime(now_delta(1), seconds=120)
+
     def test_sub_python_is_this_python(self):
         # Try it with a Python command.
         os.environ['COV_FOOBAR'] = 'XYZZY'