Class IteratorTester<E>


  • @GwtCompatible
    public abstract class IteratorTester<E>
    extends AbstractIteratorTester<E,​java.util.Iterator<E>>
    A utility for testing an Iterator implementation by comparing its behavior to that of a "known good" reference implementation. In order to accomplish this, it's important to test a great variety of sequences of the Iterator.next(), Iterator.hasNext() and Iterator.remove() operations. This utility takes the brute-force approach of trying all possible sequences of these operations, up to a given number of steps. So, if the caller specifies to use n steps, a total of 3^n tests are actually performed.

    For instance, if steps is 5, one example sequence that will be tested is:

    1. remove();
    2. hasNext()
    3. hasNext();
    4. remove();
    5. next();

    This particular order of operations may be unrealistic, and testing all 3^5 of them may be thought of as overkill; however, it's difficult to determine which proper subset of this massive set would be sufficient to expose any possible bug. Brute force is simpler.

    To use this class the concrete subclass must implement the AbstractIteratorTester.newTargetIterator() method. This is because it's impossible to test an Iterator without changing its state, so the tester needs a steady supply of fresh Iterators.

    If your iterator supports modification through remove(), you may wish to override the verify() method, which is called after each sequence and is guaranteed to be called using the latest values obtained from AbstractIteratorTester.newTargetIterator().

    • Constructor Detail

      • IteratorTester

        protected IteratorTester​(int steps,
                                 java.lang.Iterable<? extends IteratorFeature> features,
                                 java.lang.Iterable<E> expectedElements,
                                 AbstractIteratorTester.KnownOrder knownOrder)
        Creates an IteratorTester.
        Parameters:
        steps - how many operations to test for each tested pair of iterators
        features - the features supported by the iterator