/* TestHelper.java */

/**
 *  This class is based on code from Arnow and Weiss.  Its verify() method
 *  exits with an error message if an invariant fails to hold true.
 *
 *  The purpose of this class is to provide a shorthand for writing and testing
 *  invariants in any program.
 **/

public class TestHelper {

  /**
   *  verify() checks an invariant and prints an error message if it fails.
   *  If invariant is true, this method does nothing.  If invariant is false,
   *  the message is printed, followed by a dump of the program call stack.
   *  @param invariant the condition to be verified
   *  @param message the error message to be printed if the invariant fails to
   *  hold true.
   **/

  static void verify(boolean invariant, String message) {
    if (!invariant) {
      System.out.println("*** ERROR:  " + message);
      Thread.dumpStack();
    }
  }

}