Contract Testing 101
Marie Drake
Quality Engineering Manager, Zoopla
@mcruzdrake | mariedrake.com
A Simple Service
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Unit Testing
- Do not give us the confidence to release
- Mock provider might not be the true representation of the real provider
- Broken changes can be deployed
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Integration Testing
- Becomes complex in microservices
- Slow and brittle
- Requires dedicated environments where services are integrated with one another
- Lots of maintenance required
- Broken changes can be deployed
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"How do you test a fire alarm?"
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Contract Testing?
A form of testing where you test the contract between the services communicating to each other.
- Consumer
- Provider
- Pact/Contract
- Pact Broker
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Pact https://pact.io/
A consumer driven contract testing tool
Pact tests the integration points that are actually use by the consumer(s).
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How does it work? (Consumer)
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How does it work? (Provider)
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Benefits of Contract Testing
- Fast feedback
- Run independently
- Less maintenance required
- Gives us confidence to release
- Doesn't need integrated environments to check the contract
- Contract acts as a source of truth (additional documentation)
- Evolve codebases continuously knowing that Pact will ensure contracts are satisfied.
- Stop over reliance to slow integration or UI tests
- Ensures that only parts of the API that will actually be used will be developed
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When not to use Pact or Contract Testing?
- If there are no buy-ins from teams
- Public APIs where you don't know who your consumers are
- Third Party APIs
And remember...
- Not a replacement for functional testing
- Not a replacement for performance testing
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