What are the steps to reproduce your problem?
1. process definition with timer start event
2. timer definition references a bean, e.g.

${timerCycle}

3. the unit test, using ProcessEngineRule, Mocks.register and @Deployment

What is the problem?
When Mocks.register is declared in @Before method, the deployment fails, as before-method is too late to mock the bean for timer start event

What would be the expected behavior:
We should document this peculiarity and give a hint in the docs of how this can be overcome.

Hints (optional):
Another JUnit rule could be created and the rule chain could be built with ProcessEngineRule