Implementation of Constraint Handler

How to Implement a Constraint Handler

In order to implement a new constraint handler in CCAG, you need to create a class that implements the ConstraintHandler interface.

public interface ConstraintHandler {
  // the set of supported constraint handlers
  enum Handlers {
    Verify, Solver, Replace, Tolerate
  }

  /**
   * The process executed before test suite generation.
   * @param model the test model of CT
   */
  void pre(CTModel model);

  /**
   * The process executed after test suite generation.
   * @param model the test model of CT
   * @param ts the generated test suite
   */
  void post(CTModel model, TestSuite ts);

  /**
   * Determine whether a given complete or partial test case is constraints
   * satisfying. Any unfixed parameter should be assigned to value -1.
   * @param test a complete or partial test case
   * @return validity of the test case
   */
  boolean isValid(final int[] test);

  /**
   * Calculate the number of violations in the candidate solution. Any unfixed
   * parameter should be assigned to value -1.
   * @param test a complete or partial test case
   * @return number of constraints violations
   */
  long penaltyTerm(final int[] test);
}

Specifically, the pre() and post() are the two methods that will be executed before and after test suite generation (namely, before and after invoking the process() method of CAGenerator), respectively. While the isValid() and penaltyTerm() are the methods that will be used to deal with constraints during test suite generation (namely, in the process() method).

	Verify	Solver	Tolerate	Replace
pre	Calculate MFTs	Initialise a SAT Solver	Calculate MFTs	Calculate MFTs
isValid	Check against MFTs	Solve a constraint satisfaction problem	True	True
penaltyTerm	Zero	Zero	Calculate based on MFTs	Zero
post	None	None	None	Replace invalid test cases

We have implemented four constraint handlers, including Verify, Solver, Replace, and Tolerate, in CCAG as off-the-shelf choices. The concrete methods implemented in these four constraint handlers are shown in the above table.