diff --git a/mercurial/context.py b/mercurial/context.py
--- a/mercurial/context.py
+++ b/mercurial/context.py
@@ -1112,56 +1112,7 @@
     Additionally, if `skipchild` is True, replace all other lines with parent
     annotate data as well such that child is never blamed for any lines.
 
-    >>> oldfctx = b'old'
-    >>> p1fctx, p2fctx, childfctx = b'p1', b'p2', b'c'
-    >>> olddata = b'a\nb\n'
-    >>> p1data = b'a\nb\nc\n'
-    >>> p2data = b'a\nc\nd\n'
-    >>> childdata = b'a\nb2\nc\nc2\nd\n'
-    >>> diffopts = mdiff.diffopts()
-
-    >>> def decorate(text, rev):
-    ...     return ([(rev, i) for i in xrange(1, text.count(b'\n') + 1)], text)
-
-    Basic usage:
-
-    >>> oldann = decorate(olddata, oldfctx)
-    >>> p1ann = decorate(p1data, p1fctx)
-    >>> p1ann = _annotatepair([oldann], p1fctx, p1ann, False, diffopts)
-    >>> p1ann[0]
-    [('old', 1), ('old', 2), ('p1', 3)]
-    >>> p2ann = decorate(p2data, p2fctx)
-    >>> p2ann = _annotatepair([oldann], p2fctx, p2ann, False, diffopts)
-    >>> p2ann[0]
-    [('old', 1), ('p2', 2), ('p2', 3)]
-
-    Test with multiple parents (note the difference caused by ordering):
-
-    >>> childann = decorate(childdata, childfctx)
-    >>> childann = _annotatepair([p1ann, p2ann], childfctx, childann, False,
-    ...                          diffopts)
-    >>> childann[0]
-    [('old', 1), ('c', 2), ('p2', 2), ('c', 4), ('p2', 3)]
-
-    >>> childann = decorate(childdata, childfctx)
-    >>> childann = _annotatepair([p2ann, p1ann], childfctx, childann, False,
-    ...                          diffopts)
-    >>> childann[0]
-    [('old', 1), ('c', 2), ('p1', 3), ('c', 4), ('p2', 3)]
-
-    Test with skipchild (note the difference caused by ordering):
-
-    >>> childann = decorate(childdata, childfctx)
-    >>> childann = _annotatepair([p1ann, p2ann], childfctx, childann, True,
-    ...                          diffopts)
-    >>> childann[0]
-    [('old', 1), ('old', 2), ('p2', 2), ('p2', 2), ('p2', 3)]
-
-    >>> childann = decorate(childdata, childfctx)
-    >>> childann = _annotatepair([p2ann, p1ann], childfctx, childann, True,
-    ...                          diffopts)
-    >>> childann[0]
-    [('old', 1), ('old', 2), ('p1', 3), ('p1', 3), ('p2', 3)]
+    See test-annotate.py for unit tests.
     '''
     pblocks = [(parent, mdiff.allblocks(parent[1], child[1], opts=diffopts))
                for parent in parents]
diff --git a/tests/test-annotate.py b/tests/test-annotate.py
new file mode 100644
--- /dev/null
+++ b/tests/test-annotate.py
@@ -0,0 +1,75 @@
+from __future__ import absolute_import
+from __future__ import print_function
+
+import unittest
+
+from mercurial import (
+    mdiff,
+)
+from mercurial.context import (
+    _annotatepair,
+)
+
+class AnnotateTests(unittest.TestCase):
+    """Unit tests for annotate code."""
+
+    def testannotatepair(self):
+        self.maxDiff = None # camelcase-required
+
+        oldfctx = b'old'
+        p1fctx, p2fctx, childfctx = b'p1', b'p2', b'c'
+        olddata = b'a\nb\n'
+        p1data = b'a\nb\nc\n'
+        p2data = b'a\nc\nd\n'
+        childdata = b'a\nb2\nc\nc2\nd\n'
+        diffopts = mdiff.diffopts()
+
+        def decorate(text, rev):
+            return ([(rev, i) for i in xrange(1, text.count(b'\n') + 1)], text)
+
+        # Basic usage
+
+        oldann = decorate(olddata, oldfctx)
+        p1ann = decorate(p1data, p1fctx)
+        p1ann = _annotatepair([oldann], p1fctx, p1ann, False, diffopts)
+        self.assertEqual(p1ann[0], [('old', 1), ('old', 2), ('p1', 3)])
+
+        p2ann = decorate(p2data, p2fctx)
+        p2ann = _annotatepair([oldann], p2fctx, p2ann, False, diffopts)
+        self.assertEqual(p2ann[0], [('old', 1), ('p2', 2), ('p2', 3)])
+
+        # Test with multiple parents (note the difference caused by ordering)
+
+        childann = decorate(childdata, childfctx)
+        childann = _annotatepair([p1ann, p2ann], childfctx, childann, False,
+                                 diffopts)
+        self.assertEqual(childann[0],
+            [('old', 1), ('c', 2), ('p2', 2), ('c', 4), ('p2', 3)]
+        )
+
+        childann = decorate(childdata, childfctx)
+        childann = _annotatepair([p2ann, p1ann], childfctx, childann, False,
+                                 diffopts)
+        self.assertEqual(childann[0],
+            [('old', 1), ('c', 2), ('p1', 3), ('c', 4), ('p2', 3)]
+        )
+
+        # Test with skipchild (note the difference caused by ordering)
+
+        childann = decorate(childdata, childfctx)
+        childann = _annotatepair([p1ann, p2ann], childfctx, childann, True,
+                                 diffopts)
+        self.assertEqual(childann[0],
+            [('old', 1), ('old', 2), ('p2', 2), ('p2', 2), ('p2', 3)]
+        )
+
+        childann = decorate(childdata, childfctx)
+        childann = _annotatepair([p2ann, p1ann], childfctx, childann, True,
+                                 diffopts)
+        self.assertEqual(childann[0],
+            [('old', 1), ('old', 2), ('p1', 3), ('p1', 3), ('p2', 3)]
+        )
+
+if __name__ == '__main__':
+    import silenttestrunner
+    silenttestrunner.main(__name__)