Guicey provides extensions for

You may choose one or use all in one project: for example, if you already have junit4 or spock tests you can write new tests in junit5.

Junit5 and spock extensions are almost equivalent in features. Junit4 extensions are deprecated (same as dropwizard's own junit4 extensions).

All extensions implemented with DropwizardTestSupport.

Configuration hooks

Guicey provides hooks mechanism to be able to modify application configuration in tests.

Using hooks you can disable installers, extensions, guicey bundles
or override guice bindings.

It may also be useful to register additional extensions (e.g. to validate some internal behaviour).

Example hook:

public class MyHook implements GuiceyConfigurationHook {

    public void configure(GuiceBundle.Builder builder) {
            .modulesOverride(new MockDaoModule())
            .option(Myoptions.DebugOption, true);


You can modify options in hook and so could enable some custom debug/monitoring options specifically for test.

There are special spock and junit extensions for hooks registrations.


You can use hooks to disable all not needed features in test:

This way you can isolate (as much as possible) some feature for testing.

The most helpful should be bundles disable (if you use bundles for features grouping) and guice modules.

Use predicate disabling.


It is supposed that disabling will be used instead of mocking - you simply remove what you don't need and register replacements, if required.

Guice bindings override

It is quite common requirement to override bindings for testing. For example, you may want to mock database access.

Guicey could use guice Modules.override() to help you override required bindings. To use it prepare module only with changed bindings (bindings that must override existing). For example, you want to replace ServiceX. You have few options:

  • If it implement interface, implement your own service and bind as bind(ServiceContract.class).to(MyServiceXImpl.class)
  • If service is a class, you can modify its behaviour with extended class bind(ServiceX.class).to(MyServiceXExt.class)
  • Or you can simply register some mock instance bind(ServiceX.class).toInstance(myMockInstance)
public class MyOverridingModule extends AbstractModule {

    protected configure() {

And register overriding module in hook:

public class MyHook implements GuiceyConfigurationHook {
    public void configure(GuiceBundle.Builder builder) {
            .modulesOverride(new MyOverridingModule());

Debug bundles

You can also use special guicey bundles, which modify application behaviour. Bundles could contain additional listeners or services to gather additional metrics during tests or validate behaviour.

For example, guicey tests use bundle to enable restricted guice options like disableCircularProxies.

Bundles are also able to:

  • disable installers, extensions, gucie modules
  • override guice bindings

You can also use lookup mechanism to load bundles in tests. For example, system properties lookup.

Overriding overridden beans

Guicey provides direct support for overriding guice bindings, so in most cases you don't need to do anything.

But, if you use this to override application bindings need to override such bindings in test (again), then you may use provided custom injector factory:

Register factory in guice bundle:

    .injectorFactory(new BindingsOverrideInjectorFactory())

After that you can register overriding bindings (which will override even modules registered in modulesOverride) with:

BindingsOverrideInjectorFactory.override(new MyOverridingModule())


It is assumed that overrding modules registration and application initialization will be at the same thread (ThreadLocal used for holding registered modules to allow parallel tests usage).

For example, suppose we have some service CustomerService and it's implementation CustomerServiceImpl, defined in some 3rd party module. For some reason we need to override this binding in the application:

public class OverridingModule extends AbstractModule {
    protected void configure() {

If we need to override this binding in test (again):

(Simplified) registration looks like this:

    .injectorFactory(new BindingsOverrideInjectorFactory())
    .modules(new ThirdPatyModule())
    // override binding for application needs
    .modulesOverride(new OverridingModule())

// register overriding somewhere
BindingsOverrideInjectorFactory.override(new TestOverridingModule())    


Configuration hook may be used for static call (as a good integration point)

After test startup, application will use customer service binding from TestOverridingModule.