取得 runtime 時，所有的class?!

擷取 GHUnit 裡面的code....

- (NSArray *)loadAllTestCases {

  NSMutableArray *testCases = [NSMutableArray array];

  int count = objc_getClassList(NULL, 0);

  NSMutableData *classData = [NSMutableData dataWithLength:sizeof(Class) * count];

  Class *classes = (Class*)[classData mutableBytes];

  NSAssert(classes, @"Couldn't allocate class list");

  objc_getClassList(classes, count);

  

  for (int i = 0; i < count; ++i) {

    Class currClass = classes[i];

    id testcase = nil;

    

    if ([self isTestCaseClass:currClass]) {

      testcase = [[currClass alloc] init];

    } else {

      continue;

    }

    

    [testCases addObject:testcase];

  }

  

  return [testCases sortedArrayUsingFunction:ClassSort context:NULL];

}