Advanced testing
On this page 8 topics
Overview
Topics
- Contract testing
- consumer-driven contracts
- property-based testing
Learn first
3 h of practice (estimate)
Learning outcomes
- Explain why end-to-end tests across many services are slow and brittle.
- Write consumer-driven contract tests for HTTP and messaging (Pact or Spring Cloud Contract).
- Verify provider contracts in CI and block breaking changes.
- Write property-based tests (jqwik) for domain invariants.
Lessons
Lab and exercises
Lab
MID-045-LAB1 · Contracts for Shop
Outcomes: 1–4 · Time: ~3 h Write contracts between orders and inventory (HTTP) and for OrderPlaced (Kafka), verified in both pipelines. Add jqwik property tests for the Order aggregate. Acceptance: renaming a field fails the provider build.
Exercises (assessment: lab plus a test-strategy question)
| ID | Outcome | Task |
|---|---|---|
| MID-045-EX01 | 1 | List the problems of an end-to-end test that places an order across four services; propose which checks move lower. |
| MID-045-EX02 | 2 | Write a consumer test in orders producing a Pact (or Spring Cloud Contract) for GET /stock/{sku}. |
| MID-045-EX03 | 2 | Rewrite a contract that asserts a whole response body so it matches only the fields used. |
| MID-045-EX04 | 2 | Write a message contract for OrderPlaced and verify it in the producer. |
| MID-045-EX05 | 3 | Add contract verification to the provider pipeline so a failure blocks the build. |
| MID-045-EX06 | 4 | Write two jqwik properties for the Order aggregate (total equals sum of lines; total never negative). |
| MID-045-EX07 | 1–3 | Test-strategy question: for a new payments service called by orders, state which tests you write at each level and why. |
Show solutions
- EX01 Slow, brittle, hard to diagnose; move validation to unit tests, interactions to contract tests, DB behavior to Testcontainers; keep one smoke test.
- EX02 Define the interaction (request, response with
skustring andavailableinteger) in the consumer test; the generated file is published. - EX03 Replace exact body matching with type matchers on
skuandavailableonly. - EX04 Message contract with
orderIdandtotalCents; the provider test builds the real event and checks it against the contract. - EX05 Pipeline step runs provider verification against published contracts; non-zero exit fails the job.
- EX06
@Propertywith a generator of valid orders; assertions as in the lecture; second property:total() >= 0. - EX07 Unit tests for payment rules, consumer contract with
payments, Testcontainers for persistence, a smoke test; end-to-end only for the happy path.
Outcome 3 is also checked by lab criterion "renaming a field fails the provider build".
Quiz
Outcomes: O1 limits of end-to-end tests · O2 consumer-driven contracts · O3 contracts in CI · O4 property-based tests.
A self-check for you: nothing is graded, saved or sent anywhere. Choose an answer, then check it. You can try again as often as you like.
Practical part
Seven exercises MID-045-EX01 to EX07 (EX07 is the test-strategy question) plus the contracts lab. Pass: at least five exercises and a lab where renaming a field fails the provider build.
Common mistakes
Contracts written by the provider alone; asserting entire payloads.
Assessment
Lab plus test-strategy question.
Career relevance
API evolution (MID-062) and quality strategy at Staff level.