1 files changed, 18 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/semantics/embedded-content/the-iframe-element/support/iframe_sandbox_block_modals.js b/testing/web-platform/tests/html/semantics/embedded-content/the-iframe-element/support/iframe_sandbox_block_modals.js
new file mode 100644
index 0000000000..67733d8101
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/embedded-content/the-iframe-element/support/iframe_sandbox_block_modals.js
@@ -0,0 +1,18 @@
+function runTest(modalName, expectedValue) {
+    let timeOutForFailingToOpenModal = 500;
+    let startTime;
+    async_test(t => {
+        let iframe = document.querySelector("iframe");
+        iframe.onload = t.step_func(() => {
+            window.addEventListener("message", t.step_func_done(e => {
+                // This tests work by checking the call to open the modal diaglog will return immediately (or at least within timeOutForFailingToOpenModal).
+                // If the modal dialog is not blocked, then it will wait for user input and the test will time out.
+                assert_less_than(new Date().getTime() - startTime, timeOutForFailingToOpenModal, "Call to open modal dialog did not return immediately");
+                assert_equals(e.data, expectedValue, "Call to open modal dialog did not return expected value");
+            }));
+            startTime = new Date().getTime();
+            iframe.contentWindow.postMessage(modalName, "*");
+        });
+        iframe.src = "support/iframe-that-opens-modals.html";
+    }, "Frames without `allow-modals` should not be able to open modal dialogs");
+}