Intra-class testing refers to the testing of the interaction among methods and data structures encapsulated within a single class. Our approach to intra-class testing is to execute sequences of instance methods that are derived from sequencing constraints and evaluate their results for correctness. These constraints impose restrictions on method behaviors and can be derived from a formal or informal specification of a class. We present an empirical evaluation of different method sequence generation approaches, and analyze their effectiveness in detecting software faults. In addition, we define a number of coverage criteria based on method sequencing constraints for a class and examine the differences between them.