Paramaterizing Tests

Introduction#

Sometimes you have a test you need to run multiple times, each time with different data. Parameterizing the test allows you to do this in an easy and maintainable way.

Syntax#

@RunWith(Parameterized.class) //annotation for test class

@Parameters//annotation for data

Remarks#

One benefit to using parameters is that if one set of data fails, execution will just move to the next set of data instead of stopping the whole test.

Using a Constructor

import static org.junit.Assert.assertThat;
import static org.hamcrest.CoreMatchers.is;
import java.util.*;
import org.junit.*;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;

@RunWith(Parameterized.class)
public class SimpleParmeterizedTest {
    @Parameters
    public static Collection<Object[]> data(){
        return Arrays.asList(new Object[][]{
                {5, false}, {6, true}, {8, true}, {11, false}    
        });
    }
    
    private int input;
    private boolean expected;
    
    public SimpleParmeterizedTest(int input, boolean expected){
        this.input = input;
        this.expected = expected;
    }
    
    @Test
    public void testIsEven(){
        assertThat(isEven(input), is(expected));
    }
}

In data() you supply the data to be used in the tests. Junit will iterate through the data and run the test with each set of data.