org.mockito

Interface MockSettings

All Superinterfaces:

Serializable

All Known Implementing Classes:

MockSettingsImpl

public interface MockSettings
extends Serializable

Allows mock creation with additional mock settings.

Don't use it too often. Consider writing simple tests that use simple mocks. Repeat after me: simple tests push simple, KISSy, readable & maintainable code. If you cannot write a test in a simple way - refactor the code under test.

Examples of mock settings:

   //Creates mock with different default answer & name
   Foo mock = mock(Foo.class, withSettings()
       .defaultAnswer(RETURNS_SMART_NULLS)
       .name("cool mockie"));
       
   //Creates mock with different default answer, descriptive name and extra interfaces
   Foo mock = mock(Foo.class, withSettings()
       .defaultAnswer(RETURNS_SMART_NULLS)
       .name("cool mockie")
       .extraInterfaces(Bar.class));    
 

MockSettings has been introduced for two reasons. Firstly, to make it easy to add another mock setting when the demand comes. Secondly, to enable combining together different mock settings without introducing zillions of overloaded mock() methods.

Method Summary

Methods

Modifier and Type	Method and Description
MockSettings	defaultAnswer(Answer defaultAnswer) Specifies default answers to interactions.
MockSettings	extraInterfaces(Class<?>... interfaces) Specifies extra interfaces the mock should implement.
MockSettings	name(String name) Specifies mock name.
MockSettings	serializable() Configures the mock to be serializable.
MockSettings	spiedInstance(Object instance) Specifies the instance to spy on.

Method Detail

extraInterfaces

MockSettings extraInterfaces(Class<?>... interfaces)

Specifies extra interfaces the mock should implement. Might be useful for legacy code or some corner cases. For background, see issue 51 here

This mysterious feature should be used very occasionally. The object under test should know exactly its collaborators & dependencies. If you happen to use it often than please make sure you are really producing simple, clean & readable code.

Examples:

   Foo foo = mock(Foo.class, withSettings().extraInterfaces(Bar.class, Baz.class));
   
   //now, the mock implements extra interfaces, so following casting is possible:
   Bar bar = (Bar) foo;
   Baz baz = (Baz) foo;
 

Parameters:

interfaces - extra interfaces the should implement.

Returns:

settings instance so that you can fluently specify other settings

name

MockSettings name(String name)

Specifies mock name. Naming mocks can be helpful for debugging - the name is used in all verification errors.

Beware that naming mocks is not a solution for complex code which uses too many mocks or collaborators. If you have too many mocks then refactor the code so that it's easy to test/debug without necessity of naming mocks.

If you use @Mock annotation then you've got naming mocks for free! @Mock uses field name as mock name. Read more.

Examples:

   Foo foo = mock(Foo.class, withSettings().name("foo"));
   
   //Below does exactly the same:
   Foo foo = mock(Foo.class, "foo");
 

Parameters:

name - the name of the mock, later used in all verification errors

Returns:

settings instance so that you can fluently specify other settings

spiedInstance

MockSettings spiedInstance(Object instance)

Specifies the instance to spy on. Makes sense only for spies/partial mocks. Sets the real implementation to be called when the method is called on a mock object.

As usual you are going to read the partial mock warning: Object oriented programming is more less tackling complexity by dividing the complexity into separate, specific, SRPy objects. How does partial mock fit into this paradigm? Well, it just doesn't... Partial mock usually means that the complexity has been moved to a different method on the same object. In most cases, this is not the way you want to design your application.

However, there are rare cases when partial mocks come handy: dealing with code you cannot change easily (3rd party interfaces, interim refactoring of legacy code etc.) However, I wouldn't use partial mocks for new, test-driven & well-designed code.

Enough warnings about partial mocks, see an example how spiedInstance() works:

   Foo foo = mock(Foo.class, spiedInstance(fooInstance));
   
   //Below does exactly the same:
   Foo foo = spy(fooInstance);
 

Parameters:

instance - to spy on

Returns:

settings instance so that you can fluently specify other settings

defaultAnswer

MockSettings defaultAnswer(Answer defaultAnswer)

Specifies default answers to interactions. It's quite advanced feature and typically you don't need it to write decent tests. However it can be helpful when working with legacy systems.

It is the default answer so it will be used only when you don't stub the method call.

   Foo mock = mock(Foo.class, withSettings().defaultAnswer(RETURNS_SMART_NULLS));
   Foo mockTwo = mock(Foo.class, withSettings().defaultAnswer(new YourOwnAnswer()));
   
   //Below does exactly the same:
   Foo mockTwo = mock(Foo.class, new YourOwnAnswer());
 

Parameters:

defaultAnswer - default answer to be used by mock when not stubbed

Returns:

settings instance so that you can fluently specify other settings

serializable

MockSettings serializable()

Configures the mock to be serializable. With this feature you can use a mock in a place that requires dependencies to be serializable.

WARNING: This should be rarely used in unit testing.

The behaviour was implemented for a specific use case of a BDD spec that had an unreliable external dependency. This was in a web environment and the objects from the external dependency were being serialized to pass between layers.

Example:

   List serializableMock = mock(List.class, withSettings().serializable());
 

Returns:

settings instance so that you can fluently specify other settings