diff --git a/quic/quartc/quartc_interval_counter_test.cc b/quic/quartc/quartc_interval_counter_test.cc
new file mode 100644
index 0000000..9bc9af5
--- /dev/null
+++ b/quic/quartc/quartc_interval_counter_test.cc
@@ -0,0 +1,110 @@
+// Copyright (c) 2018 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/third_party/quiche/src/quic/quartc/quartc_interval_counter.h"
+
+#include "testing/gmock/include/gmock/gmock.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "net/third_party/quiche/src/quic/core/quic_interval.h"
+#include "net/third_party/quiche/src/quic/platform/api/quic_test.h"
+
+namespace quic {
+namespace {
+
+class QuartcIntervalCounterTest : public QuicTest {
+ protected:
+  QuartcIntervalCounter<int> counter_;
+};
+
+void ExpectCount(const QuartcIntervalCounter<int>& counter,
+                 QuicInterval<int> interval,
+                 size_t count) {
+  for (int i = interval.min(); i < interval.max(); ++i) {
+    EXPECT_EQ(counter.Count(i), count) << "i=" << i;
+  }
+}
+
+TEST_F(QuartcIntervalCounterTest, InitiallyEmpty) {
+  EXPECT_EQ(counter_.MaxCount(), 0u);
+}
+
+TEST_F(QuartcIntervalCounterTest, SameInterval) {
+  counter_.AddInterval(QuicInterval<int>(0, 6));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 6), 1);
+
+  counter_.AddInterval(QuicInterval<int>(0, 6));
+  EXPECT_EQ(counter_.MaxCount(), 2u);
+  ExpectCount(counter_, QuicInterval<int>(0, 6), 2);
+}
+
+TEST_F(QuartcIntervalCounterTest, DisjointIntervals) {
+  counter_.AddInterval(QuicInterval<int>(0, 5));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 5), 1);
+  ExpectCount(counter_, QuicInterval<int>(5, 10), 0);
+
+  counter_.AddInterval(QuicInterval<int>(5, 10));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 5), 1);
+  ExpectCount(counter_, QuicInterval<int>(5, 10), 1);
+}
+
+TEST_F(QuartcIntervalCounterTest, OverlappingIntervals) {
+  counter_.AddInterval(QuicInterval<int>(0, 6));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 6), 1);
+  ExpectCount(counter_, QuicInterval<int>(6, 10), 0);
+
+  counter_.AddInterval(QuicInterval<int>(5, 10));
+  EXPECT_EQ(counter_.MaxCount(), 2u);
+  ExpectCount(counter_, QuicInterval<int>(0, 5), 1);
+  EXPECT_EQ(counter_.Count(5), 2u);
+  ExpectCount(counter_, QuicInterval<int>(6, 10), 1);
+}
+
+TEST_F(QuartcIntervalCounterTest, IntervalsWithGapThenOverlap) {
+  counter_.AddInterval(QuicInterval<int>(0, 4));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 4), 1);
+  ExpectCount(counter_, QuicInterval<int>(4, 10), 0);
+
+  counter_.AddInterval(QuicInterval<int>(7, 10));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 4), 1);
+  ExpectCount(counter_, QuicInterval<int>(4, 7), 0);
+  ExpectCount(counter_, QuicInterval<int>(7, 10), 1);
+
+  counter_.AddInterval(QuicInterval<int>(3, 8));
+  EXPECT_EQ(counter_.MaxCount(), 2u);
+  ExpectCount(counter_, QuicInterval<int>(0, 3), 1);
+  EXPECT_EQ(counter_.Count(3), 2u);
+  ExpectCount(counter_, QuicInterval<int>(4, 7), 1);
+  EXPECT_EQ(counter_.Count(7), 2u);
+  ExpectCount(counter_, QuicInterval<int>(8, 10), 1);
+}
+
+TEST_F(QuartcIntervalCounterTest, RemoveIntervals) {
+  counter_.AddInterval(QuicInterval<int>(0, 5));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 5), 1);
+
+  counter_.AddInterval(QuicInterval<int>(4, 10));
+  EXPECT_EQ(counter_.MaxCount(), 2u);
+  ExpectCount(counter_, QuicInterval<int>(0, 4), 1);
+  EXPECT_EQ(counter_.Count(4), 2u);
+  ExpectCount(counter_, QuicInterval<int>(5, 10), 1);
+
+  counter_.RemoveInterval(QuicInterval<int>(0, 5));
+  EXPECT_EQ(counter_.MaxCount(), 1u);
+  ExpectCount(counter_, QuicInterval<int>(0, 5), 0);
+  ExpectCount(counter_, QuicInterval<int>(5, 10), 1);
+
+  counter_.RemoveInterval(QuicInterval<int>(5, 10));
+  EXPECT_EQ(counter_.MaxCount(), 0u);
+  ExpectCount(counter_, QuicInterval<int>(0, 10), 0);
+}
+
+}  // namespace
+}  // namespace quic