Теория Юнита для хэш-кода/равна контракту

Следующий класс служит универсальным тестером для контракта equals/hashCode. Это часть среды, разработанной для взрослых.

• О чем вы думаете?
• Как я могу (сильный) протестировать этот класс?
• Это хорошее использование теорий Junit?

Класс:

@Ignore
@RunWith(Theories.class)
public abstract class ObjectTest {

    // For any non-null reference value x, x.equals(x) should return true
    @Theory
    public void equalsIsReflexive(Object x) {
        assumeThat(x, is(not(equalTo(null))));
        assertThat(x.equals(x), is(true));
    }

    // For any non-null reference values x and y, x.equals(y) 
    // should return true if and only if y.equals(x) returns true.
    @Theory
    public void equalsIsSymmetric(Object x, Object y) {
        assumeThat(x, is(not(equalTo(null))));
        assumeThat(y, is(not(equalTo(null))));
        assumeThat(y.equals(x), is(true));
        assertThat(x.equals(y), is(true));
    }

    // For any non-null reference values x, y, and z, if x.equals(y)
    // returns true and y.equals(z) returns true, then x.equals(z) 
    // should return true.
    @Theory
    public void equalsIsTransitive(Object x, Object y, Object z) {
        assumeThat(x, is(not(equalTo(null))));
        assumeThat(y, is(not(equalTo(null))));
        assumeThat(z, is(not(equalTo(null))));
        assumeThat(x.equals(y) && y.equals(z), is(true));
        assertThat(z.equals(x), is(true));
    }

    // For any non-null reference values x and y, multiple invocations
    // of x.equals(y) consistently return true  or consistently return
    // false, provided no information used in equals comparisons on
    // the objects is modified.
    @Theory
    public void equalsIsConsistent(Object x, Object y) {
        assumeThat(x, is(not(equalTo(null))));
        boolean alwaysTheSame = x.equals(y);

        for (int i = 0; i < 30; i++) {
            assertThat(x.equals(y), is(alwaysTheSame));
        }
    }

    // For any non-null reference value x, x.equals(null) should
    // return false.
    @Theory
    public void equalsReturnFalseOnNull(Object x) {
        assumeThat(x, is(not(equalTo(null))));
        assertThat(x.equals(null), is(false));
    }

    // Whenever it is invoked on the same object more than once 
    // the hashCode() method must consistently return the same 
    // integer.
    @Theory
    public void hashCodeIsSelfConsistent(Object x) {
        assumeThat(x, is(not(equalTo(null))));
        int alwaysTheSame = x.hashCode();

        for (int i = 0; i < 30; i++) {
            assertThat(x.hashCode(), is(alwaysTheSame));
        }
    }

    // If two objects are equal according to the equals(Object) method,
    // then calling the hashCode method on each of the two objects
    // must produce the same integer result.
    @Theory
    public void hashCodeIsConsistentWithEquals(Object x, Object y) {
        assumeThat(x, is(not(equalTo(null))));
        assumeThat(x.equals(y), is(true));
        assertThat(x.hashCode(), is(equalTo(y.hashCode())));
    }

    // Test that x.equals(y) where x and y are the same datapoint 
    // instance works. User must provide datapoints that are not equal.
    @Theory
    public void equalsWorks(Object x, Object y) {
        assumeThat(x, is(not(equalTo(null))));
        assumeThat(x == y, is(true));
        assertThat(x.equals(y), is(true));
    }

    // Test that x.equals(y) where x and y are the same datapoint instance
    // works. User must provide datapoints that are not equal.
    @Theory
    public void notEqualsWorks(Object x, Object y) {
        assumeThat(x, is(not(equalTo(null))));
        assumeThat(x != y, is(true));
        assertThat(x.equals(y), is(false));
    }
}

использование:

import org.junit.experimental.theories.DataPoint;

public class ObjectTestTest extends ObjectTest {

    @DataPoint
    public static String a = "a";
    @DataPoint
    public static String b = "b";
    @DataPoint
    public static String nullString = null;
    @DataPoint
    public static String emptyString = "";
}

Ответы

@DataPoint
public static String a = "a";
@DataPoint
public static String a2 = new String("a");