Implemented a new sequence number unwrapper in sequence_number_util.h.

webrtc/rtc_base/mod_ops_unittest.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 69 matching lines @@
   }
 
   int yi = 255;
   for (int i = 0; i < 256; ++i) {
     ASSERT_EQ(255u, ForwardDiff<uint8_t>(x, yi));
     ++x;
     ++yi;
   }
 }
 
+TEST_F(TestModOps, ForwardDiffWithDivisor) {
+  const uint8_t kDiv = 123;
+  uint8_t x = 0;
+  uint8_t y = kDiv - 1;
+  for (int i = 0; i < kDiv; ++i) {
+    ASSERT_EQ(kDiv - 1, (ForwardDiff<uint8_t, kDiv>(x, y)));
+    x = (x + 1) % kDiv;
+    y = (y + 1) % kDiv;
+  }

[Taylor Brandstetter, 2017/07/25 21:33:05]

nit: I don't like how these tests are written; they duplicate logic by the code
under test and it's not immediately obvious that they're correct. I would have
written them to test a few representative values, including corner cases. For
example:

ASSERT_EQ(122, ForwardDiff<uint8_t, 123>(0, 122));
ASSERT_EQ(122, ForwardDiff<uint8_t, 123>(1, 0));
ASSERT_EQ(1, ForwardDiff<uint8_t, 123>(122, 0));

And maybe even split these into separate tests cases.

See:
https://engdoc.corp.google.com/eng/doc/devguide/coding/testing/unit-testing-b...

Though the rest of the existing tests do the same thing as the new tests. So you
can decide whether to go for consistency or "good test design". At a minimum it
would be nice to have a TODO though.

[philipel, 2017/07/26 09:52:15]

Better to start using better test design. Updated the tests with simpler logic.

+}
+
 TEST_F(TestModOps, ReverseDiff) {
   ASSERT_EQ(0u, ReverseDiff(4711u, 4711u));
 
   uint8_t x = 0;
   uint8_t y = 255;
   for (int i = 0; i < 256; ++i) {
     ASSERT_EQ(1u, ReverseDiff(x, y));
     ++x;
     ++y;
   }
 
   int yi = 255;
   for (int i = 0; i < 256; ++i) {
     ASSERT_EQ(1u, ReverseDiff<uint8_t>(x, yi));
     ++x;
     ++yi;
   }
 }
 
+TEST_F(TestModOps, ReverseDiffWithDivisor) {
+  const uint8_t kDiv = 13;
+  uint8_t x = 0;
+  uint8_t y = kDiv - 1;
+  for (int i = 0; i < kDiv; ++i) {
+    ASSERT_EQ(1, (ReverseDiff<uint8_t, kDiv>(x, y)));
+    x = (x + 1) % kDiv;
+    y = (y + 1) % kDiv;
+  }
+}
+
 TEST_F(TestModOps, MinDiff) {
   for (uint16_t i = 0; i < 256; ++i) {
     ASSERT_EQ(0, MinDiff<uint8_t>(i, i));
     ASSERT_EQ(1, MinDiff<uint8_t>(i - 1, i));
     ASSERT_EQ(1, MinDiff<uint8_t>(i + 1, i));
   }
 
   for (uint8_t i = 0; i < 128; ++i)
     ASSERT_EQ(i, MinDiff<uint8_t>(0, i));
 
@@ skipping 12 matching lines @@
   for (uint16_t i = 0; i < D / 2; ++i)
     ASSERT_EQ(i, (MinDiff<uint16_t, D>(0, i)));
 
   ASSERT_EQ(D / 2, (MinDiff<uint16_t, D>(0, D / 2)));
 
   for (uint16_t i = 0; i < D / 2; ++i)
     ASSERT_EQ(D / 2 - i, (MinDiff<uint16_t, D>(0, D / 2 - i)));
 }
 
 }  // namespace webrtc