diff --git a/testing/web-platform/tests/html/semantics/forms/form-submission-0/SubmitEvent.window.js b/testing/web-platform/tests/html/semantics/forms/form-submission-0/SubmitEvent.window.js
new file mode 100644
index 0000000000000..93dbabb866bee
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/forms/form-submission-0/SubmitEvent.window.js
@@ -0,0 +1,36 @@
+// https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#the-submitevent-interface
+
+test(() => {
+  let button = document.createElement('button');
+  let typeError = new TypeError();
+  assert_throws(typeError, () => { new SubmitEvent() }, '0 arguments');
+  assert_throws(typeError, () => { new SubmitEvent('bar', button) }, '1 invalid arguments');
+  assert_throws(typeError, () => { new SubmitEvent(button, button) }, '2 invalid arguments');
+  assert_throws(typeError, () => { new SubmitEvent('foo', null) }, 'Null dictionary');
+  assert_throws(typeError, () => { new SubmitEvent('foo', undefined) }, 'Undefined dictionary');
+  assert_throws(typeError, () => { new SubmitEvent('foo', { submitter: null }) }, 'Null submitter');
+  assert_throws(typeError, () => { new SubmitEvent('foo', { submitter: undefined }) }, 'Undefined submitter');
+  assert_throws(typeError, () => { new SubmitEvent('foo', { submitter: 'bar' }) }, 'Wrong type of submitter');
+}, 'Failing SubmitEvent constructor');
+
+test(() => {
+  let button = document.createElement('button');
+  let event = new SubmitEvent('bar', { submitter: button, bubbles: true });
+  assert_equals(event.submitter, button);
+  assert_true(event.bubbles);
+}, 'Successful SubmitEvent constructor');
+
+test(() => {
+  let event = new SubmitEvent('bar', { submitter: null});
+  assert_equals(event.submitter, null);
+}, 'Successful SubmitEvent constructor; null submitter');
+
+test(() => {
+  let event = new SubmitEvent('baz', {});
+  assert_equals(event.submitter, null);
+}, 'Successful SubmitEvent constructor; empty dictionary');
+
+test(() => {
+  let event = new SubmitEvent('baz');
+  assert_equals(event.submitter, null);
+}, 'Successful SubmitEvent constructor; missing dictionary');
diff --git a/testing/web-platform/tests/html/semantics/forms/form-submission-0/form-submission-algorithm.html b/testing/web-platform/tests/html/semantics/forms/form-submission-0/form-submission-algorithm.html
index 8f61cbc18c951..df39b57353c67 100644
--- a/testing/web-platform/tests/html/semantics/forms/form-submission-0/form-submission-algorithm.html
+++ b/testing/web-platform/tests/html/semantics/forms/form-submission-0/form-submission-algorithm.html
@@ -50,6 +50,60 @@
   });
 }, "If form's firing submission events is true, then return; 'submit' event");
 
+promise_test(async () => {
+  let form = populateForm('<button type=submit></button><input name=n1 value=submit type=submit>');
+  let iframe = form.previousSibling;
+  let submitter = form.querySelector('input[type=submit]');
+  let event;
+  form.addEventListener('submit', e => { event = e; });
+  submitter.click();
+  await loadPromise(iframe);
+  assert_true(event.bubbles);
+  assert_true(event.cancelable);
+  assert_equals(event.submitter, submitter);
+  assert_true(event instanceof SubmitEvent);
+}, 'firing an event named submit; clicking a submit button');
+
+promise_test(async () => {
+  let form = populateForm('');
+  let iframe = form.previousSibling;
+  let event;
+  form.addEventListener('submit', e => { event = e; });
+  form.requestSubmit();
+  await loadPromise(iframe);
+  assert_true(event.bubbles);
+  assert_true(event.cancelable);
+  assert_equals(event.submitter, null);
+  assert_true(event instanceof SubmitEvent);
+}, 'firing an event named submit; form.requestSubmit()');
+
+promise_test(async () => {
+  let form = populateForm('');
+  let iframe = form.previousSibling;
+  let event;
+  form.addEventListener('submit', e => { event = e; });
+  form.requestSubmit(null);
+  await loadPromise(iframe);
+  assert_true(event.bubbles);
+  assert_true(event.cancelable);
+  assert_equals(event.submitter, null);
+  assert_true(event instanceof SubmitEvent);
+}, 'firing an event named submit; form.requestSubmit(null)');
+
+promise_test(async () => {
+  let form = populateForm('<input type=submit><button type=submit></button>');
+  let iframe = form.previousSibling;
+  let submitter = form.querySelector('button');
+  let event;
+  form.addEventListener('submit', e => { event = e; });
+  form.requestSubmit(submitter);
+  await loadPromise(iframe);
+  assert_true(event.bubbles);
+  assert_true(event.cancelable);
+  assert_equals(event.submitter, submitter);
+  assert_true(event instanceof SubmitEvent);
+}, 'firing an event named submit; form.requestSubmit(submitter)');
+
 async_test(t => {
   let form = populateForm('<input name=n1 value=v1>');
   form.onformdata = (e) => { e.target.remove(); };
diff --git a/testing/web-platform/tests/html/semantics/forms/form-submission-0/implicit-submission.optional.html b/testing/web-platform/tests/html/semantics/forms/form-submission-0/implicit-submission.optional.html
new file mode 100644
index 0000000000000..109d3b901a535
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/forms/form-submission-0/implicit-submission.optional.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<link rel="help" href="https://html.spec.whatwg.org/C/#implicit-submission">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/testdriver.js"></script>
+<script src="/resources/testdriver-vendor.js"></script>
+<script src="./resources/targetted-form.js"></script>
+<body>
+<script>
+// This test file is "optional" because triggering implicit submission by
+// "Enter" key is not standardized.
+
+const ENTER = '\uE007';
+
+promise_test(async () => {
+  let form = populateForm('<input name=text value=abc><input name=submiButton type=submit>');
+  let event;
+  form.text.focus();
+  form.addEventListener('submit', e => { event = e; });
+  await test_driver.send_keys(form.text, ENTER);
+  assert_true(event.bubbles);
+  assert_true(event.cancelable);
+  assert_equals(event.submitter, form.submitButton);
+  assert_true(event instanceof SubmitEvent);
+}, 'Submit event with a submit button');
+
+promise_test(async () => {
+  let form = populateForm('<input name=text value=abc>');
+  let event;
+  form.text.focus();
+  form.addEventListener('submit', e => { event = e; });
+  await test_driver.send_keys(form.text, ENTER);
+  assert_true(event.bubbles);
+  assert_true(event.cancelable);
+  assert_equals(event.submitter, null);
+  assert_true(event instanceof SubmitEvent);
+}, 'Submit event with no submit button');
+</script>
+</body>
diff --git a/testing/web-platform/tests/html/semantics/forms/form-submission-0/resources/targetted-form.js b/testing/web-platform/tests/html/semantics/forms/form-submission-0/resources/targetted-form.js
index 6b6685291d2bd..291251b7e8037 100644
--- a/testing/web-platform/tests/html/semantics/forms/form-submission-0/resources/targetted-form.js
+++ b/testing/web-platform/tests/html/semantics/forms/form-submission-0/resources/targetted-form.js
@@ -19,3 +19,10 @@ function submitPromise(form, iframe) {
     form.submit();
   });
 }
+
+function loadPromise(iframe) {
+  return new Promise((resolve, reject) => {
+    iframe.onload = resolve;
+    iframe.onerror = () => reject(new Error('iframe onerror fired'));
+  });
+}