Test It Before You Ship It: Java API Testing Lab

09:00 – 10:15

Draw the pyramid for your own service

what each test layer buys, cost of each layer, mapping your current suite

Takeaway Your own suite mapped onto the pyramid, with the gaps named out loud, which is the plan for the two days.

10:30 – 11:45

Write unit tests that earn their keep

JUnit 5 lifecycle, parameterised tests, AssertJ assertions that explain failure

Takeaway A failing test whose message alone tells you the bug: no debugger, no print statements.

12:00 – 13:00

Isolate with Mockito, without mocking everything

mocks vs stubs vs fakes, Mockito verify used sparingly, the over-mocked smell

Takeaway One over-mocked test rewritten until it tests behaviour instead of implementation, and survives a refactor to prove it.

14:00 – 15:15

Test the web slice with Spring Boot Test

@WebMvcTest with MockMvc, validation and error contracts, security in slices

Takeaway Controller tests that fail when a status code, error shape or validation rule quietly changes.

15:30 – 17:00

Test the data layer against the real thing

@DataJpaTest with Testcontainers, real PostgreSQL vs H2, migrations under test

Takeaway The data layer tested on real PostgreSQL in a container, and the bug H2 would have hidden, demonstrated.

09:00 – 10:15

Boot the whole service in a test

@SpringBootTest honestly costed, WireMock for third-party edges, context caching

Takeaway A full-context integration test that earns its runtime, and the suite reorganised so only a few need to.

10:30 – 11:45

Drive the API from the outside with REST Assured

REST Assured given/when/then, asserting the contract, auth in outside-in tests

Takeaway The API exercised exactly as a client would, with the error contract asserted, not assumed.

12:00 – 13:00

Automate scenarios with Karate

Karate feature files, data-driven scenarios, where Karate beats code

Takeaway A readable scenario file a non-developer could review, running against the same API, in CI like everything else.

14:00 – 15:15

Make the suite one you can trust

flaky tests to root cause, Awaitility for async assertions, test data builders

Takeaway A planted flaky test hunted to its cause: time, order and shared state all interrogated on the way.

15:30 – 17:00

Turn it into a gate and defend it

the suite in GitHub Actions, JaCoCo coverage read honestly, review

Takeaway The whole pyramid running as a CI gate that blocks a real planted regression, and the argument for each layer, made to the room.