Working with JUnit ErrorCollector

A common practice when developing tests with JUnit is to use assertions. But this comes with a drawback, since when an assert fails, the whole test fails, leaving some tests conditions untested. The ErrorCollector comes to address this problem. As its name suggests, it collects all the assert statements. When an assert failure is found it proceeds with the next statements and only returns the failure at the end of the test.

Example

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.core.Is.is;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ErrorCollector;

public class TestErrorCollector {
    @Rule
    public final ErrorCollector collector = new ErrorCollector();

    @Test
    public void testWithAssert() {
        assertEquals(1, 2);
        assertTrue(false);
        assertFalse(false);
    }

    @Test
    public void testWithErrorCollector() {
        collector.checkThat(1, equalTo(2));
        collector.checkThat(true, is(false));
        collector.checkThat(false, is(false));
    }
}

Results

The method testWithAssert will produce the following result:

The above result means that assertEquals(1, 2) failed and the following assert statements were not tested.

The method testWithErrorCollector will produce the following result:

The above result means that all assert statements were tested two failed and one has passed the test

Summary

• JUnit rule ErrorCollector allows test continuity even after one test condition has failed
• Test continuity and recovery is crucial for a test automation process
• All errors will be reported at the end of test
• Don’t forget to add @Rule annotation
• ErrorCollector must be public, otherwise it will throws a ValidationError