About Mike Miller

Mike is a software developer who loves to learn how things work. A Java programmer who caught the Groovy & Grails itch and is always looking for opportunities to include them as part of the solution.

Parameterized JUnit tests

Sometimes you encounter a problem that just screams for using “parameterized” tests rather than copy/pasting the same method many times.   The test method is basically the same and the only thing that changes is the data passed in.  In this case, consider creating a test case that utilitizes the ” Parameterized” class from JUnit.

I recently ran into a problem where our validation of an email address did not allow unicode characters.  The fix was fairly straight-forward, change the regular expression to allow those characters.  Next, it was time to test the change.  Rather than copy/paste separate methods for each set of data, I decided to learn about the Parameterized method.   Below is the result.  The data includes the expected result and the email address to be validated.

JUnit test class

package com.mycompany.client;
import static org.junit.Assert.*;
import java.util.Arrays;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;
import org.junit.runners.Parameterized.Parameters;
import com.mycompany.test.TestServiceUtil;
 * Parameterized test case for validating email addresses against a regular expression.
 * We need to allow unicode characters in the userid portion of the email address, so 
 * these test cases where created to help validate the validateEmailAddress method
 * in the FieldValidationController class.
 * @author mmiller
public class TestFieldValiationController {
    @Parameters(name = "{index}: {1} is valid email address = {0}")
    public static Iterable<Object> data() {
        return Arrays.asList(new Object[][] { 
         { true, "john@mycomp.com" },           { true,  "john123@mycomp.com" },
         { true, "j+._%20_-brown@mycomp.com" }, { true,  "123@mycomp.com" },
         { false, "john brown@mycomp.com" },    { false, "123@mycomp" },
         { false, "john^brown@mycomp.com" },    { true , "1john@mycomp.com" },
         { false, "john#brown@mycomp.com" },    { false, "john!brown@mycomp.com" },
         { false, "john()brown@mycomp.com" },   { false, "john=brown@mycomp.com" },
         { true,  "johñ.brown@mycomp.com" },    { false, "john.brown@mycomp.coñ" },
         { true,  "johú@mycomp.com" },          { true,  "johíáó@mycomp.com" }
    private boolean expected;
    private String emailAddress;
    public TestFieldValiationController(boolean expected, String emailAddress) {
        this.expected = expected;
        this.emailAddress = emailAddress;
    public void validateEmail() {
        assertEquals(expected, FieldValidationController.getInstance().validateEmailAddress(emailAddress));

Hope this helps!

Reference: Parameterized JUnit tests from our JCG partner Mike Miller at the Scratching my programming itch blog.
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3 Responses to "Parameterized JUnit tests"

  1. ks says:

    I assume the line 46 is redundant?

  2. Christian says:

    Parametrization of tests is easier with TestNG.

  3. Artur Szeja says:

    You didn’t mention that the functionality of customized test names is available since JUnit 4.11

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