#import "generic.h" @interface NSObject (PretendToBeNSString) - (NSUInteger)length; @end @implementation NSObject(TestAdditions) -(BOOL)testEquals:(id)anObject { return ([self isEqual:anObject] && [anObject isEqual:self]); } - (NSUInteger) length { return 0; } -(BOOL)testForString { return ([self isKindOfClass:[NSString class]] && [self length]); } @end