@@ -84,12 +84,14 @@
 	TEST(@"-[intersectSet:]",
 	    R([mutableSet intersectSet: ([OFSet setWithObjects: @"baz",
 	    nil])]) && [mutableSet isEqual: ([OFSet setWithObjects: @"baz",
 	    nil])])
 
-	[mutableSet addObject: @"baz"];
-	[mutableSet addObject: @"x"];
+	TEST(@"-[unionSet:]",
+	    R([mutableSet unionSet: ([OFSet setWithObjects: @"x", @"bar",
+	    nil])]) && [mutableSet isEqual: ([OFSet setWithObjects: @"baz",
+	    @"bar", @"x", nil])])
 
 #ifdef OF_HAVE_FAST_ENUMERATION
 	ok = YES;
 	i = 0;