Beginning with version 0.8, junit-quickcheck supports the usual JUnit machinery on interface default methods (@Property, @Before, @After, @Rule), interface static methods (@BeforeClass, @AfterClass, @ClassRule), and interface fields (@ClassRule).
As with JUnit 5, this allows for tests for interface contracts:
public interface ComparatorContract<T> {
Comparator<T> subject();
@Property default void symmetry(T x, T y) {
Comparator<T> subject = subject();
assertEquals(
signum(subject.compare(x, y)),
-signum(subject.compare(y, x)),
0F);
}
}
@RunWith(JUnitQuickcheck.class)
public class StringCaseInsensitiveProperties
implements ComparatorContract<String> {
@Override public Comparator<String> subject() {
return String::compareToIgnoreCase;
}
}
public interface ComparableVersusEqualsContract<T extends Comparable<T>> {
T thingComparableTo(T thing);
@Property default void equalsConsistency(T thing) {
T other = thingComparableTo(thing);
assumeThat(thing.compareTo(other), equalTo(0));
assertEquals(thing, other);
}
}
@RunWith(JUnitQuickcheck.class)
public class StringProperties
implements ComparableVersusEqualsContract<String> {
@Override public String thingComparableTo(String s) {
return new String(s.toCharArray());
}
}