...

import static org.onlab.junit.UtilityClassChecker.assertThatClassIsUtility;
 
/**
  * Check that the Criteria class is a valid utility class.
  */
@Test
public void testCriteriaUtility() {
    assertThatClassIsUtility(Criteria.class);
}

...

Construction and Retrieval Tests

A basic test for each one of your constructors and a check for the values returned by data access methods should always be included

...

    /**
     * Checks the construction of a FlowId object.
     */
    @Test
    public void testConstruction() {
        final long flowIdValue = 7777L;
        final FlowId flowId = FlowId.valueOf(flowIdValue);
        assertThat(flowId, is(notNullValue()));
        assertThat(flowId.value(), is(flowIdValue));
    }

...

Hamcrest

Hamcrest is a powerful framework for defining matchers for data values in tests. ONOS uses version 1.3 of Hamcrest. Contributors are encouraged to learn about and use the Hamcrest framework, particularly when working with arrays and collections. Hamcrest also gives you the ability to write your own matchers, which will make your tests easier to read and easier to extend by other developers.