1 files changed, 26 insertions, 0 deletions
diff --git a/testing/web-platform/tests/css/css-scroll-snap-2/resources/programmatic-scroll-common.js b/testing/web-platform/tests/css/css-scroll-snap-2/resources/programmatic-scroll-common.js
new file mode 100644
index 0000000000..8257b98fe3
--- /dev/null
+++ b/testing/web-platform/tests/css/css-scroll-snap-2/resources/programmatic-scroll-common.js
@@ -0,0 +1,26 @@
+// Helper functions for snapchanged-on-programmatic-* tests.
+
+// Utility function to test that onsnapchanging is triggered for
+// snapchanging-on-programmatic-* tests which set up a similar layout in which
+// the |scroller| has 3 snap targets that form a vertical column along
+// |scroller|'s middle. onsnapchanging should be triggered by conducting a
+// programmatic scroll to the top of snap_target.
+async function test_programmatic_scroll_onsnapchanging(test,
+                                                       scroller,
+                                                       event_target,
+                                                       snap_target) {
+  await snap_test_setup(test, scroller, "snapchanging");
+  const expected_snap_targets = { block: snap_target, inline: null };
+
+  // Scroll and wait for a snapchanging event.
+  const snapchanging_promise = waitForOnSnapchanging(event_target);
+  scroller.scrollTo(0, snap_target.offsetTop);
+  const snapchanging_event = await snapchanging_promise;
+
+  // Assert that snapchanging fired and indicated that snap_target would
+  // be snapped to.
+  assertSnapEvent(snapchanging_event, expected_snap_targets);
+  assert_equals(scroller.scrollLeft, 0, "scrollLeft is zero");
+  assert_equals(scroller.scrollTop, snap_target.offsetTop,
+    "snapped to snap_target");
+}