@@ -77,10 +77,15 @@
 
 - (void)testCopy
 {
 	OTAssertEqualObjects([[_set copy] autorelease], _set);
 }
+
+- (void)testMutableCopy
+{
+	OTAssertEqualObjects([[_set mutableCopy] autorelease], _set);
+}
 
 - (void)testIsSubsetOfSet
 {
 	OTAssertTrue([([OFSet setWithObjects: @"foo", nil])
 	    isSubsetOfSet: _set]);