test: add vtt parser tests for invalid timestamps, cue settings and multiline cues

static/player/subtitles/vtt.test.ts

@@ -28,4 +28,31 @@ World
       { start: 2, end: 3, text: "World" },
     ]);
   });
+
+  test("returns zero for invalid timestamps", () => {
+    assert.equal(parseVttTime(""), 0);
+    assert.equal(parseVttTime("not a timestamp"), 0);
+    assert.equal(parseVttTime("00:bad"), 0);
+  });
+
+  test("ignores cue settings and strips html tags", () => {
+    const cues = parseVtt(`WEBVTT
+
+00:10.000 --> 00:12.000 align:start position:0%
+<b>Bold</b> & plain
+`);
+
+    assert.deepEqual(cues, [{ start: 10, end: 12, text: "Bold & plain" }]);
+  });
+
+  test("joins multiline cue text", () => {
+    const cues = parseVtt(`WEBVTT
+
+00:00.000 --> 00:03.000
+First line
+Second line
+`);
+
+    assert.deepEqual(cues, [{ start: 0, end: 3, text: "First line\nSecond line" }]);
+  });
 });