The case for consumer-driven contracts

1. The case for consumer-driven contracts @matthewfellows

2. Picture the scene...

3. Monday morning

4. 9am

5. Phone rings

6. It’s our VC

7. We just got the news....

9. We’re going to build a startup!

11. Soundify ®

12. Everyone is doing microservices!

14. Metric Value No. teams 1 No. components 1 Test environments 1 Time in pipeline (commit to prod) 5 minutes Risk 2.5% Deployments per day 10 CD health check

16. Metric Value No. teams 2 No. components 2 Test environments 4 Time in pipeline (commit to prod) 10 minutes Risk 5% Deployments per day 10 CD health check

19. Metric Value No. teams 3 No. components 6 Test environments 18 Time in pipeline (commit to prod) 30 minutes Risk 10% Deployments per day 10 CD health check

20. ACQUIRED

22. Metric Value No. teams 10 No. components 20 Test environments 20 200 Time in pipeline (commit to prod) 120+ minutes Risk 20% Deployments per day 1 CD health check

23. So what did we learn?

25. Where did we go wrong?

26. We pretended microservices were colocated libraries

27. Cohesive services, loosely coupled vs Cohesive teams, tightly coupled by services

28. Current tooling and strategies are not good enough

29. “Integration tests are a scam” - JB Rainsberger

30. Scam, you say? Justify! Integrated tests are: ● Slow ● Fragile ● Hard to manage When they fail, you can’t point to the problem!

31. Scam, you say? Justify! “But my integration tests run in Docker, why can’t I use them?” - People

32. Scam, you say? Justify! “Because Maths” - Me

34. Branches per box vs test cases required 2 code branches = 128 tests 5 code branches = 78,125 tests 10 code branches = 10M tests

35. Good tests have the exact opposite properties

37. Dictator Driven Contracts

38. Dictator Driven Contracts

39. 1. Sit in ivory tower and postulate 2. Document perfect API (Swagger, API blueprint etc.) 3. Create said API 4. Publish said document to consumers 5. Request dictate consumers update 6. Repeat steps 1-5 How to: Dictator Driven Contracts

43. Crap, this didn’t work either!

44. Dictator Consumer Driven Contracts

46. Benefits?

47. You’ll know when you break a consumer

48. You have a form of documentation

49. You can test things independently

50. Pact www.pact.io

51. Evolved from combining these two principles

52. Step 1: Define Consumer expectations

55. Step 1: Define Consumer expectations Step 2: Verify expectations on Provider

56. Start with a consumer test

57. Given “User A exists” When I Receive “a GET request for user A” With “these headers and query” Respond with “200 OK” And “User A’s details in the body”

58. Given “User A does not exist” When I Receive “a GET request for user A” Respond with “404 Not Found”

59. Example

60. // Setup our expected interactions on the Mock Service. pact. AddInteraction(). Given("User billy exists"). UponReceiving("A request to login with user 'billy'"). WithRequest(dsl.Request{ Method: "POST", Path: "/users/login", Body: loginRequest, }). WillRespondWith(dsl.Response{ Status: 200, Headers: map[string]string{ "Content-Type": "application/json", }, Body: ` { "user": { "name": "billy" } } `, })

61. // Run the test and verify the interactions. err := pact.Verify(func() error { client := Client{ Host: fmt.Sprintf("http://localhost:%d", pact.Server.Port), } client.loginHandler(rr, req) // Expect User to be set on the Client if client.user == nil { return errors.New("Expected user not to be nil") } return nil }) if err != nil { t.Fatalf("Error on Verify: %v", err) } // Write pact to file `<pwd>/pacts/my_consumer-my_provider.json` // NOTE: This also is a good candidate for use in TestMain(m *testing.M) pact.WritePact()

62. Specification by example

63. { "consumer": {"name": "MyConsumer"}, "provider": {"name": "MyProvider"}, "interactions": [ { "description": "Some name for the test", "provider_state": "Some state", "request": { "method": "GET", "path": "/foobar", "headers": { "Content-Type": "application/json" }, "body": { "s": "foo" } }, "response": { "status": 200, "headers": { "Content-Type": "application/json" }, "body": { "s": "bar" } } } ... ]

68. Next publish your pacts

72. // Publish the Pacts... p := dsl.Publisher{} err := p.Publish(types.PublishRequest{ PactURLs: []string{"../pacts/myconsumer-myprovider.json"}, PactBroker: os.Getenv("PACT_BROKER_HOST"), ConsumerVersion: "1.0.0", Tags: []string{"latest", "production"}, BrokerUsername: os.Getenv("PACT_BROKER_USERNAME"), BrokerPassword: os.Getenv("PACT_BROKER_PASSWORD"), })

73. Then verify your provider

75. // Verify the Provider from tagged Pact files stored in a Pact Broker response = pact.VerifyProvider(types.VerifyRequest{ ProviderBaseURL: fmt.Sprintf("http://localhost:%d", providerPort), BrokerURL: brokerHost, Tags: []string{"latest", "prod"}, ProviderStatesURL: fmt.Sprintf("http://localhost:%d/states", providerPort), ProviderStatesSetupURL: fmt.Sprintf("http://localhost:%d/setup", providerPort), BrokerUsername: os.Getenv("PACT_BROKER_USERNAME"), BrokerPassword: os.Getenv("PACT_BROKER_PASSWORD"), }) if response.ExitCode != 0 { t.Fatalf("Got %d, Want exit code 0", response.ExitCode) }

76. Verifying a pact between billy and bobby Given User billy exists A request to login with user 'billy' with POST /users/login returns a response which has status code 200 has a matching body includes headers "Content-Type" with value "application/json" Given User billy does not exist A request to login with user 'billy' with POST /users/login returns a response which has status code 404 includes headers "Content-Type" with value "application/json" ... Finished in 0.03042 seconds 7 examples, 0 failures

79. Verifying a pact between billy and bobby Given User billy exists A request to login with user 'billy' with POST /users/login returns a response which has status code 200 has a matching body (FAILED - 1) includes headers "Content-Type" with value "application/json" Failures: 1) Verifying a pact between billy and bobby Given User billy exists A request to login with user 'billy' with POST /users/login returns a response which has a matching body Failure/Error: expect(response_body).to match_term expected_response_body, diff_options Actual: {"user":{"user":"billy"}} @@ -1,6 +1,5 @@ { "user": { - "name": "billy" } }

80. No Silver Bullet

81. Does not replace communication

83. What about systems maintained by other teams?

84. What about systems built in outdated technologies?

85. Scary outside world! 3rd Party Mainframe

86. Recapping... ● Business impact of integrated tests ● Cause and explanation of those effects ● Alternative approach - isolation + contracts ● Contract-testing as an approach, Pact as a tool (in this order!)

87. Thank you - @matthewfellows Given “The presentation is over” Upon Receiving “A request for an answer” With “A valid question” Respond With “A valid answer”

The case for consumer-driven contracts

More Related Content

Similar to The case for consumer-driven contracts (20)

More from DiUS (20)

Recently uploaded (20)

The case for consumer-driven contracts