Unit Testing Runtime Exceptions with JUnit4 and Hamcrest

Junit and Hamcrest make unit testing with Java almost enjoyable. In this post, I show how to unit test Exceptions with JUnit4 and Hamcrest. In this over-simplified example, I'm testing a method that always throws an IllegalArgumentException. In real-life the IllegalArgumentException would only be thrown under special circumstances given certain arguments, and those are the ones you want to test with the unit test.

The basic idea is to surround the method you want to test with a try catch block and pass it an argument that will trigger the IllegalArgumentException to be thrown. The fail method call should never be reached, and if it does the unit test should fail. What should happen is that the IllegalArgumentException is caught, followed by a check for the correct message.

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.junit.Assert.fail;

import org.junit.Test;

/**
 * The following example code demonstrates how to unit test Exceptions with JUnit and Hamcrest
 */
public class ExceptionUnitTesting {

  @Test
  public void test() {

    try {
      blah("asdf");
      fail("Expected exception");
    } catch (IllegalArgumentException e) {
      assertThat(e.getMessage(), is(equalTo("Argument foo is not valid!")));
    }
  }

  /**
   * @param foo
   * @throws IllegalArgumentException - in this test case always
   */
  private void blah(String foo) {

    throw new IllegalArgumentException("Argument foo is not valid!");
  }
}

Piece of Cake!!!

Import a Maven Git Project Into Eclipse

The Easy Way

Prerequisites
Install M2Eclipse

Step 1: Clone or create Git Repo. First, you need to clone a Git repo into an empty folder in your workspace. You need to use a Git client such as SourceTree or TortoiseGit for this. Create you workspace first if it isn't already, and clone the git repo directly into a new folder labeled with the project name.

Step 2: Import Into Eclipse. In the Package Explorer view, right-click and choose Import... In the wizard choose Maven -> "Existing Maven Projects" as the project type. Search for the project home directory and click though the wizard.

The Hard Way

Prerequisites
Install M2Eclipse
Install egit

Step 1: Right-click in the Package Explorer area and select Import..., select Maven -> Check out Maven Projects from SCM, and click Next.

Step 2: Choose "git" as the SCM connector next to "SCM URL:" and type in the Git repo URL. If there are no connectors to choose from you have to first install that Eclipse plugin. To do that, click on the "m2e Marketplace" link in the lower right hand corner of the dialog box.

Step 3: Check m2e-egit and click Finish.

Step 4: Select "git" as the SCM connector and type in the Git repo URL.

Step 5: After asking you for the passphrase for ssh access to the Git repo, it will download and import the Java project as a Maven project into your workspace.

Piece of Cake!!!