How can I test final and static methods of a utility project?

Question

I'm trying to implement unit testing for aproject, it uses a legacy "utility" project that is littered with static methods and many of the classes are final or their methods are final. I'm not able to update the legacy project at all.

JMock and EasyMock both choke on final methods, and I don't see a nice way to test the static calls. What techniques are there to test these?

Answer 1

If you're able to refactor your code, you can wrap your calls to the final/static methods in simple instance methods, for example:

protected Foo doBar(String name) {     return Utility.doBar(name); } 

This allows you to override your wrapper method in the unit test to return a mock instance of Foo.

Alternatively you can use Powermock, which extends Easymock (and Mockito) to allow mocking of final and static methods:

PowerMock is a framework that extend other mock libraries such as EasyMock with more powerful capabilities. PowerMock uses a custom classloader and bytecode manipulation to enable mocking of static methods, constructors, final classes and methods, private methods, removal of static initializers and more.

Here's an example test mocking a static final method, the example shows how to mock some other types too:

@Test public void testMockStaticFinal() throws Exception {     mockStatic(StaticService.class);     String expected = "Hello altered World";     expect(StaticService.sayFinal("hello")).andReturn("Hello altered World");     replay(StaticService.class);      String actual = StaticService.sayFinal("hello");      verify(StaticService.class);     assertEquals("Expected and actual did not match", expected, actual);      // Singleton still be mocked by now.     try {         StaticService.sayFinal("world");             fail("Should throw AssertionError!");     } catch (AssertionError e) {         assertEquals("\n  Unexpected method call sayFinal(\"world\"):",              e.getMessage());     } } 

Answer 2

How about a level of indirection / Dependency Injection?

Since the legacy utility project is your dependency, create an interface to separate it out from your code. Now your real/production implementation of this interface delegates to the legacy utility methods.

public LegacyActions : ILegacyActions {   public void SomeMethod() { // delegates to final/static legacy utility method } } 

For your tests, you can create a mock of this interface and avoid interacting with the legacy utility thingie.