diff -r 000000000000 -r 6474c204b198 dom/bindings/parser/tests/test_variadic_constraints.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/bindings/parser/tests/test_variadic_constraints.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,63 @@
+def WebIDLTest(parser, harness):
+    threw = False
+    try:
+        parser.parse("""
+            interface VariadicConstraints1 {
+              void foo(byte... arg1, byte arg2);
+            };
+        """)
+        results = parser.finish()
+
+    except:
+        threw = True
+
+    harness.ok(threw,
+               "Should have thrown on variadic argument followed by required "
+               "argument.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            interface VariadicConstraints2 {
+              void foo(byte... arg1, optional byte arg2);
+            };
+        """)
+        results = parser.finish();
+    except:
+        threw = True
+
+    harness.ok(threw,
+               "Should have thrown on variadic argument followed by optional "
+               "argument.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            interface VariadicConstraints3 {
+              void foo(optional byte... arg1);
+            };
+        """)
+        results = parser.finish()
+
+    except:
+        threw = True
+
+    harness.ok(threw,
+               "Should have thrown on variadic argument explicitly flagged as "
+               "optional.")
+
+    parser = parser.reset()
+    threw = False
+    try:
+        parser.parse("""
+            interface VariadicConstraints4 {
+              void foo(byte... arg1 = 0);
+            };
+        """)
+        results = parser.finish()
+    except:
+        threw = True
+
+    harness.ok(threw, "Should have thrown on variadic argument with default value.")