Fix behaviour of app.alert() with a single object argument.

testing/resources/javascript/app_alert.in

Index: testing/resources/javascript/app_alert.in
diff --git a/testing/resources/javascript/app_alert.in b/testing/resources/javascript/app_alert.in
index de6c8a82290b1e83d440222cfb5e9aa469e3ef6d..75aecc9075397775c30997f9a357ca9166971ef2 100644
--- a/testing/resources/javascript/app_alert.in
+++ b/testing/resources/javascript/app_alert.in
@@ -35,6 +35,32 @@ endobj
 >>
 stream
 app.alert("This test passes if alert() logs output under the test utility.");
+app.alert("message", 1, 2, "title");
+app.alert({"cMsg": "message", "cTitle": "title"});
+app.alert({"cMsg": "message", "cTitle": "title", "nIcon": 3, "nType": 4});
+app.alert(undefined);
+app.alert(null);
+app.alert(true);
+app.alert(false);
+app.alert(42);
+app.alert([1, 2, 3]);
+app.alert([1, 2, {"color": "red"}]);
+app.alert({"color": "red"}, 5, 6, "title"); 
+try {
+  app.alert();
+} catch (e) {
+  app.alert("Caught expected error " + e);
+}
+try {
+  app.alert({});
+} catch (e) {
+  app.alert("Caught expected error " + e);
+}
+try {
+  app.alert({"color": "red", "size": 42});
+} catch (e) {
+  app.alert("Caught expected error " + e);
+}
 endstream
 endobj
 {{xref}}