Discount for inactivity timeout for recording session length

chrome/browser/metrics/desktop_engagement/desktop_engagement_service_unittest.cc

 // Copyright 2016 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 "chrome/browser/metrics/desktop_engagement/desktop_engagement_service.h"
 
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/test/histogram_tester.h"
 #include "base/test/test_mock_time_task_runner.h"
@@ skipping 129 matching lines @@
   // Wait until the session expires.
   while (!instance.is_timeout()) {
     base::RunLoop().RunUntilIdle();
   }
 
   EXPECT_FALSE(instance.in_session());
   EXPECT_FALSE(instance.is_visible());
   EXPECT_FALSE(instance.is_audio_playing());
   histogram_tester.ExpectTotalCount("Session.TotalDuration", 1);
 }
+
+TEST(DesktopEngagementServiceTest, TestTimeoutDiscount) {
+  base::MessageLoop loop(base::MessageLoop::TYPE_DEFAULT);
+  base::HistogramTester histogram_tester;
+  MockDesktopEngagementService instance;
+
+  int inactivity_interval = 2;
+  instance.SetInactivityTimeoutForTesting(inactivity_interval);
+
+  instance.OnVisibilityChanged(true);
+  base::TimeTicks before_session_start = base::TimeTicks::Now();
+  instance.OnUserEvent(); // This should start the session
+  histogram_tester.ExpectTotalCount("Session.TotalDuration", 0);
+
+  // Wait until the session expires.
+  while (!instance.is_timeout()) {
+    base::RunLoop().RunUntilIdle();
+  }
+  base::TimeTicks after_session_end = base::TimeTicks::Now();
+
+  histogram_tester.ExpectTotalCount("Session.TotalDuration", 1);
+  // The recorded value should be shorter than the specified inactivity
+  // interval.
+  base::Bucket bucket =
+      histogram_tester.GetAllSamples("Session.TotalDuration")[0];
+  EXPECT_LE(
+    bucket.min + inactivity_interval,
+    (after_session_end - before_session_start).InSeconds());
+}