add test

src/util/media-sequence-sync.js

@@ -273,7 +273,7 @@ export class DependantMediaSequenceSync extends MediaSequenceSync {
     this.parent_ = parent;
   }
 
-  calculateBaseTime_(mediaSequence, fallback) {
+  calculateBaseTime_(mediaSequence, segments, fallback) {
     if (!this.storage_.size) {
       const info = this.parent_.getSyncInfoForMediaSequence(mediaSequence);
 
@@ -284,6 +284,6 @@ export class DependantMediaSequenceSync extends MediaSequenceSync {
       return 0;
     }
 
-    return super.calculateBaseTime_(mediaSequence, fallback);
+    return super.calculateBaseTime_(mediaSequence, segments, fallback);
   }
 }

test/util/media-sequence-sync.test.js

@@ -0,0 +1,109 @@
+import QUnit from 'qunit';
+import { MediaSequenceSync } from '../../src/util/media-sequence-sync';
+
+QUnit.module('MediaSequenceSync: update', function(hooks) {
+  let mediaSequenceSync;
+
+  hooks.beforeEach(function() {
+    mediaSequenceSync = new MediaSequenceSync();
+  });
+
+  QUnit.test('update calculates correct base time based on mediaSequence of new playlist', function(assert) {
+    const initialMediaSequence = 10;
+    const initialSegments = [
+      // Segment 10 with duration 5
+      { duration: 5 },
+      // Segment 11 with duration 6
+      { duration: 6 },
+      // Segment 12 with duration 7
+      { duration: 7 }
+    ];
+
+    // Initial update with starting playlist
+    mediaSequenceSync.update(
+      {
+        mediaSequence: initialMediaSequence,
+        segments: initialSegments
+      },
+      // Current time, value is used for fallback and not significant here
+      20
+    );
+
+    // Confirm that the initial update set the correct start and end times
+    assert.strictEqual(
+      mediaSequenceSync.start,
+      0,
+      'The start time is set to the initial value of 0.'
+    );
+
+    // Confirm the end time is the correct sum of the segment durations
+    // = 18
+    const expectedInitialEndTime = 0 + 5 + 6 + 7;
+
+    assert.strictEqual(
+      mediaSequenceSync.end,
+      expectedInitialEndTime,
+      'The end time is calculated correctly after the initial update.'
+    );
+
+    // New playlist with higher mediaSequence
+    let newMediaSequence = 11;
+    let newSegments = [
+      // Segment 11 with duration 4
+      { duration: 4 },
+      // Segment 12 with duration 5
+      { duration: 5 },
+      // Segment 13 with duration 6
+      { duration: 6 }
+    ];
+
+    // Update with the new playlist
+    mediaSequenceSync.update(
+      {
+        mediaSequence: newMediaSequence,
+        segments: newSegments
+      },
+      30
+    );
+
+    // Segment 10 with duration 5 has fallen off the start of the playlist
+    let expectedStartTime = 5;
+
+    assert.strictEqual(
+      mediaSequenceSync.start,
+      expectedStartTime,
+      'The base time is calculated correctly when a new playlist with a higher mediaSequence is loaded.'
+    );
+
+    // New playlist with lower mediaSequence
+    newMediaSequence = 10;
+    newSegments = [
+      // Segment 10 with duration 5
+      { duration: 5 },
+      // Segment 11 with duration 6
+      { duration: 6 },
+      // Segment 12 with duration 7
+      { duration: 7 }
+    ];
+
+    // Update with the new playlist
+    mediaSequenceSync.update(
+      {
+        mediaSequence: newMediaSequence,
+        segments: newSegments
+      },
+      40
+    );
+
+    // Expected base time is calculated by extrapolating backwards:
+    // Segment 11 start time: 5
+    // Segment 10 start time: Segment 11 start time (5) - Segment 10 duration (5) = 0
+    expectedStartTime = 0;
+
+    assert.strictEqual(
+      mediaSequenceSync.start,
+      expectedStartTime,
+      'The base time is calculated correctly when a new playlist with a lower mediaSequence is loaded.'
+    );
+  });
+});