BeanMatchers Could not generate two distinct values after 128 attempts of type java.time.Instant

Question

When I am trying to run the following test:

    @Test
    public void testHash() {
        BeanMatchers.registerValueGenerator(Instant::now, Instant.class);
        assertThat(ClassForTest.class, hasValidBeanHashCode());
    }

for the class:

class ClassForTest {
    private Instant instant;

    public Instant getInstant() {
        return instant;
    }

    public void setInstant(Instant instant) {
        this.instant = instant;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        ClassForTest that = (ClassForTest) o;
        return Objects.equals(instant, that.instant);
    }

    @Override
    public int hashCode() {
        return Objects.hash(instant);
    }
}

where BeanMatchers class comes from:

        <dependency>
            <groupId>com.google.code.bean-matchers</groupId>
            <artifactId>bean-matchers</artifactId>
            <version>0.14</version>
            <scope>test</scope>
        </dependency>

I am constantly getting the following exception:

BeanMatchers Could not generate two distinct values after 128 attempts of type java.time.Instant

Any ideas why I see this exception and how to fix it? Because, technically, the test is implemented in the right way.

Answer 1

I was facing the same issue, I resolved it like this

@Test
public void testHash() {
    BeanMatchers.registerValueGenerator(this::registerInstant, Instant.class);

    assertThat(ClassForTest.class, hasValidBeanHashCode());
}

private Instant registerInstant() {
    List<Instant> times = Arrays.asList(Instant.now(), Instant.now().minusSeconds(10));

    return times.get(new Random().nextInt(times.size()));
}