Unrecoganized selector sent to an instance while unit testing iphone app in xcode 3.1.3 ?

Question

Hi All,

I have created a sample app for AES encryption. It adds two methods to NSData as a category. But I am to build it successfully while compiling. After that I decided to unit test the app with unit test bundle. Then in the first method I added the code

- (void) testPass {

    AESKit *m_objAESKit=[[AESKit alloc] initwithUserData:@"hello123" 

        keyForEncryption:@"hello"];

    NSData *objData=[m_objAESKit encrypt];
    STAssertNotNil(objData,@"Successfully encrypted");

    [m_objAESKit release];

}

The encrypt method internally calls the category method [NSDataObject AES256EncryptWithKey:strKey];

This method fails during unit testing with message [NSConcreteMutableData AES256EncryptWithKey:] unrecoganized selector sent to an instance..

Please help..

Regards, Syam S