add failing body.onload tests

src/browser/tests/window/body_onload2.html

@@ -1,15 +1,15 @@
 <!DOCTYPE html>
-<body onload="loaded()"></body>
+<body onload="loadEvent = event"></body>
 <script src="../testing.js"></script>
 
 <script id=bodyOnLoad2>
-  let called = 0;
-  function loaded(e) {
-    called += 1;
-  }
+  // Per spec, the handler is compiled as: function(event) { loadEvent = event }
+  // Verify: handler fires, "event" parameter is a proper Event, and handler is a function.
+  let loadEvent = null;
 
   testing.eventually(() => {
-    testing.expectEqual(1, called);
+    testing.expectEqual("function", typeof document.body.onload);
+    testing.expectTrue(loadEvent instanceof Event);
+    testing.expectEqual("load", loadEvent.type);
   });
 </script>
-

src/browser/tests/window/body_onload3.html

@@ -0,0 +1,28 @@
+<!DOCTYPE html>
+<body onload="called++"></body>
+<script src="../testing.js"></script>
+
+<script id=bodyOnLoad3>
+  // Per spec, the handler is compiled as: function(event) { called++ }
+  // Verify: handler fires exactly once, and body.onload reflects to window.onload.
+  let called = 0;
+
+  testing.eventually(() => {
+    // The attribute handler should have fired exactly once.
+    testing.expectEqual(1, called);
+
+    // body.onload is a Window-reflecting handler per spec.
+    testing.expectEqual("function", typeof document.body.onload);
+    testing.expectEqual(document.body.onload, window.onload);
+
+    // Setting body.onload via property replaces the attribute handler.
+    let propertyCalled = false;
+    document.body.onload = function() { propertyCalled = true; };
+    testing.expectEqual(document.body.onload, window.onload);
+
+    // Setting onload to null removes the handler.
+    document.body.onload = null;
+    testing.expectEqual(null, document.body.onload);
+    testing.expectEqual(null, window.onload);
+  });
+</script>