First off, all the source code for this is available on github: https://github.com/activelylazy/coverage-example. I’ll show key snippets, but obviously there’s lots of detail omitted that (hopefully) isn’t relevant.
The Example App
Rather than break with tradition, the example application is a simple, if slightly contrived, hello world:
How It Works
The start page is a simple link to the hello world page:
<h1>Example app</h1> <p>See the <a id="messageLink" href="helloWorld.html">message</a></p>
The hello world page just displays the message:
<h1>Example app</h1>
<p id="message"><c:out value="${message}"/></p>
The hello world controller renders the view, passing in the message:
public class HelloWorldController extends ParameterizableViewController {
// Our message factory
private MessageFactory messageFactory;
@Override
protected ModelAndView handleRequestInternal(HttpServletRequest request,
HttpServletResponse response) throws Exception {
// Get the success view
ModelAndView mav = super.handleRequestInternal(request, response);
// Add our message
mav.addObject("message",messageFactory.createMessage());
return mav;
}
@Autowired
public void setMessageFactory(MessageFactory messageFactory) {
this.messageFactory = messageFactory;
}
}Finally the MessageFactory simply returns the hard-coded message:
public String createMessage() {
return "Hello world";
}
The unit test
We define a simple unit test to verify that the MessageFactory behaves as expected:
public class MessageFactoryTest {
// The message factory
private MessageFactory messageFactory;
@Test
public void testCreateMessage() {
assertEquals("Hello world",messageFactory.createMessage());
}
@Autowired
public void setMessageFactory(MessageFactory messageFactory) {
this.messageFactory = messageFactory;
}
}
Build
A basic maven pom file is sufficient to build this and run the unit test. At this point we have a working app, with a unit test for the core functionality (such as it is) that we can build and run.
<project>
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>helloworld</artifactId>
<packaging>war</packaging>
<version>1.0-SNAPSHOT</version>
<name>helloworld Maven Webapp</name>
<build>
<finalName>helloworld</finalName>
</build>
<dependencies>
...omitted...
</dependencies>
</project>
Code Coverage
Now let’s integrate Emma so we can get some code coverage reports. First, we define a new Maven profile, this allows us to control whether or not we use emma on any given build.
<profile>
<id>with-emma</id>
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>emma-maven-plugin</artifactId>
<inherited>true</inherited>
<executions>
<execution>
<id>instrument</id>
<phase>process-test-classes</phase>
<goals>
<goal>instrument</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
</profile>
This simply invokes the “instrument” goal during the Maven “process-test-classes” phase; i.e. once we’ve compiled our class files, use emma to instrument them. We can run this by invoking maven with the new profile:
mvn clean install -Pwith-emma
Once the build has completed, we can run Emma to generate code coverage reports:
On Windows:
java -cp %USERPROFILE%/.m2/repository/emma/emma/2.0.5312/emma-2.0.5312.jar emma report -r xml,html -in coverage.ec -in target/coverage.em
On Linux:
java -cp ~/.m2/repository/emma/emma/2.0.5312/emma-2.0.5312.jar emma report -r xml,html -in coverage.ec -in target/coverage.em
We can now view the HTML coverage report in coverage/index.html. At this point, it shows we have 50% test coverage (by classes). MessageFactory is fully covered, but the HelloWorldController doesn’t have any tests at all.
Integration Test
To test our controller and JSP, we’ll use WebDriver to create a simple integration test; this is a JUnit test that happens to launch a browser.
public class HelloWorldIntegrationTest {
// The webdriver
private static WebDriver driver;
@BeforeClass
public static void initWebDriver() {
driver = new FirefoxDriver();
}
@AfterClass
public static void stopSeleniumClent() {
try {
driver.close();
driver.quit();
} catch( Throwable t ) {
// Catch error & log, not critical for tests
System.err.println("Error stopping driver: "+t.getMessage());
t.printStackTrace(System.err);
}
}
@Test
public void testHelloWorld() {
// Start from the homepage
driver.get("http://localhost:9080/helloworld/");
HomePage homePage = new HomePage(driver);
HelloWorldPage helloWorldPage = homePage.clickMessageLink();
assertEquals("Hello world",helloWorldPage.getMessage());
}
}
Lines 4-18 simply start Web Driver before the test and shut it down (closing the browser window) once the test is finished.
On line 22 we navigate to the homepage with a hard-coded URL.
On line 23 we initialise our Web Driver page object for the homepage. This encapsulates all the details of how the page works, allowing the test to interact with the page functionally, without worrying about the mechanics (which elements to use etc).
On line 24 we use the homepage object to click the “message” link; this navigates to the hello world page.
On line 25 we confirm that the message shown on the hello world page is what we expect.
Note: I’m using page objects to separate test specification (what to do) from test implementation (how to do it). For more on why this is important see keeping tests from being brittle.
Homepage
The homepage object is pretty simple:
public HelloWorldPage clickMessageLink() {
driver.findElement(By.id("messageLink")).click();
return new HelloWorldPage(driver);
}
HelloWorldPage
The hello world page is equally simple:
public String getMessage() {
return driver.findElement(By.id("message")).getText();
}
Running the Integration Test
To run the integration test during our Maven build we need to make a few changes. First, we need to exclude integration tests from the unit test phase:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
...
<configuration>
...
<excludes>
<exclude>**/*IntegrationTest.java</exclude>
<exclude>**/common/*</exclude>
</excludes>
</configuration>
</plugin>
Then we define a new profile, so we can optionally run integration tests:
<profile>
<id>with-integration-tests</id>
<build>
<plugins>
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<version>6.1.22</version>
<configuration>
<scanIntervalSeconds>5</scanIntervalSeconds>
<stopPort>9966</stopPort>
<stopKey>foo</stopKey>
<connectors>
<connector implementation="org.mortbay.jetty.nio.SelectChannelConnector">
<port>9080</port>
<maxIdleTime>60000</maxIdleTime>
</connector>
</connectors>
</configuration>
<executions>
<execution>
<id>start-jetty</id>
<phase>pre-integration-test</phase>
<goals>
<goal>run</goal>
</goals>
<configuration>
<daemon>true</daemon>
</configuration>
</execution>
<execution>
<id>stop-jetty</id>
<phase>post-integration-test</phase>
<goals>
<goal>stop</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.5</version>
<inherited>true</inherited>
<executions>
<execution>
<id>integration-tests</id>
<phase>integration-test</phase>
<goals>
<goal>test</goal>
</goals>
<configuration>
<excludes>
<exclude>**/common/*</exclude>
</excludes>
<includes>
<include>**/*IntegrationTest.java</include>
</includes>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</profile>
This may look complex, but really we’re just configuring jetty to run while we run our integration tests; then configuring how to run the integration tests themselves.
In lines 9-19 configure jetty – the port to run on and how to stop it.
Lines 21-30 configure jetty to run during the “pre-integration-test” phase of the maven build.
Lines 31-37 configure jetty to be stopped during the “post-integration-test” phase of the maven build.
In lines 40-62 we use the maven-surefire-plugin again, this time to run during the “integration-test” phase of the build, only running our integration test classes.
We can run this build with:
mvn clean install -Pwith-emma -Pwith-integration-tests
This will build everything, run the unit tests, build the war, fire up jetty to host the war, run our integration tests (you’ll see a firefox window popup while the rest runs) then shut down jetty. Because the war is built with instrumented classes, Emma also tracks code coverage while we run our integration tests.
We can now build our application, running unit tests and integration tests, gathering combined code coverage reports. If we re-run the emma report and check code coverage we now see we have 100% test coverage – since the controller is also being covered through tests.
Issues
What are the outstanding issues with this, what further extensions can be made?
- The build produces an instrumented WAR – this means you need to run a second build, without emma, to get a production-ready build.
- The integration test hard-codes the port that Jetty is configured to start on; meaning the tests can’t be run directly within Eclipse. It is possible to pass this port in, defaulting to say, 8080, so that integration tests can be run seemlessly within Eclipse as well via the maven build
- When running on your build server you probably don’t want Firefox popping up at random (if X is even installed); so running xvfb is a good idea. It is possible to setup maven to start & stop xvfb before & after the integration tests.
Reference: Code coverage with unit & integration tests and from our JCG partner Dave at Actively Lazy blog
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- Services, practices & tools that should exist in any software development house, part 2
- This comes BEFORE your business logic!
- How many bugs do you have in your code?
- Using FindBugs to produce substantially less buggy code
- Java Tools: Source Code Optimization and Analysis
- Things Every Programmer Should Know
- Why Automated Tests Boost Your Development Speed
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