Creating unit tests in core Liferay sources

Liferay has been catching up lately on the tests coverage. Many improvements have been made in the trunk located in liferay-portal / master branch on GitHub and since I've been fixing some things recently, I've included unit test for the changed class as well.

Quick start how-to:

1. read Liferay testing documentation to get the basic picture,
2. create your unit test in portal-impl/test/unit/.../<your_class>Test.java,
3. create test methods as usual with JUnit 4.x,
4. run the test and see results:

• cd portal-impl,
• ant test-class -Dclass=CustomJspRegistryImplTest,
• note that only the name of the class is used, not the full name including package.

Testing just a single class at a time seems to be necessary, executing ant test-unit to run all existing unit tests seems to be time consuming (from minutes to tens of minutes).

For simple tests and classes, you'll be just fine with just instantiating your tested class, calling the method and verifying the returned result:

public class CustomJspRegistryImplTest {

@Test

public void testGetCustomJspFileName_noExtension() {

Assert.assertEquals(

  "/some/absolute/non_extension_page.test-context",

_customJspRegistry.getCustomJspFileName(

    "test-context", "/some/absolute/non_extension_page"));
}

  private CustomJspRegistryImpl _customJspRegistry =

  new CustomJspRegistryImpl();

}

But what if code inside getCustomJspFileName() calls some other methods, how to ensure we're not testing their implementation instead of ours? The answer is a technique extensively used in software development: mocking. 

Wiki link above contains some basic examples of static methods' mocking. When you need to mock some instance method's call, you can use either:

1. already, fully mocked classes from libraries like spring-test, available in Liferay out of the box. Examples could be MockServletContext or MockHttpServletRequest, allowing you to tailor the objects as you need.
2. use PowerMock and Mockito libraries to mock individual calls on any class objects:

  private HttpServletRequest _getRequestWithApplicatoinAdapter(

   String adapterServletContextName) {

  MockHttpServletRequest request = new MockHttpServletRequest();

  ThemeDisplay spyThemeDisplay = spy(new ThemeDisplay());

request.setAttribute(WebKeys.THEME_DISPLAY, spyThemeDisplay);

  Group spyScopeGroup = spy(new GroupImpl());

  UnicodeProperties spyProps = spy(new UnicodeProperties());

  doReturn(spyScopeGroup).when(spyThemeDisplay).getScopeGroup();

  doReturn(spyProps).when(spyScopeGroup).getTypeSettingsProperties();

  doReturn(adapterServletContextName).when(spyProps).getProperty(
    "customJspServletContextName");

  return request;

  }

As you can see, we need to provide particular typeSetting in scope group of given HTTP request. Every time we want to mock an object's method call, we need to do two things:

1. get instrumented version of the object:
• ThemeDisplay spyThemeDisplay = spy(new ThemeDisplay());
2. say which methods we want to mock and how:
• doReturn(spyScopeGroup).when(spyThemeDisplay).getScopeGroup();
• this line could be read as: 
• whenever method getScopeGroup() is being called on our instrumented object (spyThemeDisplay),  we'll get object spyScopeGroup
• returned object spyScopeGroup could be (and in our example is) further mocked as well.

Powermock documentation contains a ton of useful examples and provides a very god entry point. Complete source of the test class I've used in this post could be found on Github.