1 files changed, 54 insertions, 0 deletions
diff --git a/testing/web-platform/tests/intersection-observer/isIntersecting-threshold.html b/testing/web-platform/tests/intersection-observer/isIntersecting-threshold.html
new file mode 100644
index 0000000000..842c8e2c9f
--- /dev/null
+++ b/testing/web-platform/tests/intersection-observer/isIntersecting-threshold.html
@@ -0,0 +1,54 @@
+<!DOCTYPE html>
+<meta name="viewport" content="width=device-width,initial-scale=1">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="./resources/intersection-observer-test-utils.js"></script>
+<style>
+#scroller { width: 100px; height: 100px; overflow: scroll; }
+#scroller > div { height: 800px; }
+#target { margin-top: 25px; height: 50px; background-color: blue; }
+</style>
+<div id="scroller">
+  <div>
+    <div id="target"></div>
+  </div>
+</div>
+
+<script>
+let entries = [];
+
+window.onload = function() {
+  runTestCycle(step2, "At initial scroll position");
+
+  scroller.scrollTop = 0;
+  let observer = new IntersectionObserver(
+    es => entries = entries.concat(es),
+    { threshold: 1 }
+  );
+  observer.observe(target);
+};
+
+function step2() {
+  runTestCycle(step3, "Scrolled to half way through target element");
+
+  assert_equals(entries.length, 1);
+  assert_equals(entries[0].intersectionRatio, 1);
+  assert_equals(entries[0].isIntersecting, true);
+  scroller.scrollTop = 50;
+}
+
+function step3() {
+  runTestCycle(step4, "Scrolled to target element completely off screen");
+
+  assert_equals(entries.length, 2);
+  assert_true(entries[1].intersectionRatio >= 0.5 &&
+              entries[1].intersectionRatio < 1);
+  // See https://github.com/w3c/IntersectionObserver/issues/432
+  assert_equals(entries[1].isIntersecting, false);
+  scroller.scrollTop = 100;
+}
+
+function step4() {
+  assert_equals(entries.length, 2);
+}
+</script>