diff -r 000000000000 -r 6474c204b198 js/src/gdb/tests/test-prettyprinters.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/gdb/tests/test-prettyprinters.py	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,22 @@
+import mozilla.prettyprinters
+
+run_fragment('prettyprinters.implemented_types')
+
+def implemented_type_names(expr):
+    v = gdb.parse_and_eval(expr)
+    it = mozilla.prettyprinters.implemented_types(v.type)
+    return [str(_) for _ in it]
+
+assert_eq(implemented_type_names('i'), ['int'])
+assert_eq(implemented_type_names('a'), ['A', 'int'])
+assert_eq(implemented_type_names('b'), ['B', 'A', 'int'])
+assert_eq(implemented_type_names('c'), ['C'])
+assert_eq(implemented_type_names('c_'), ['C_', 'C'])
+assert_eq(implemented_type_names('e'), ['E', 'C', 'D'])
+assert_eq(implemented_type_names('e_'), ['E_', 'E', 'C', 'D'])
+assert_eq(implemented_type_names('f'), ['F', 'C', 'D'])
+assert_eq(implemented_type_names('h'), ['H', 'F', 'G', 'C', 'D'])
+
+# Check that our pretty-printers aren't interfering with printing other types.
+assert_pretty('10', '10')
+assert_pretty('(void*) 0', '') # Because of 'set print address off'