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How to Test Complex API integrations

Elias Nogueira
September 07, 2022

How to Test Complex API integrations

Elias Nogueira

September 07, 2022
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  1. How to test complex API integrations Elias Nogueira JAVAZONE 2022

  2. Elias Nogueira I help professional software engineers (backend, frontend, qa)

    to develop their quality mindset and deliver bug-free software so they become top-level engineers and get hired for the best positions in the market. 🏢 Backbase 👨💻‍‍ Principal Software Engineer 📍 Utrecht, the Netherlands 🌐 eliasnogueira.com 🐦 @eliasnogueira bit.ly/eliasnogueira
  3. What problem do we want to solve?

  4. Implicitly we want … • Increase confidence in delivery •

    Cover key business scenarios • The certainty that the test will find a possible failure after some modification
  5. API anatomy (testing perspective)

  6. Individual APIs API API API API API API API API

    Each microservice is a small feature that runs in isolation.
  7. Individual APIs Unit Tests done! API API API API API

    API API API Each API must have its unit tests and integration. Integration Tests* done! * API Tests running in an integration layer with or without mocks
  8. API API API API API API The problem Integration tests

    won’t cover real scenarios of dependent APIs because of the mocks. M O CK API M O CK API
  9. Possible solution

  10. API API API API API API API API Possible solution

    Create functional tests and e2e to cover possible gaps and decrease the test on the UI. Functional Tests & E2E
  11. API API API API API API Possible solution What Add

    tests to any kind of dependencies, as well for the user journey depends consum es REAL API REAL API
  12. Analogy: buying a flight ticket

  13. Buying a flight ticket We must make sure each API

    is self-tested unit -> integration -> functional Search Flight selection Payment Confirmation API API API API
  14. Buying a flight ticket We must make sure each API

    is self-tested unit -> integration -> functional Search Flight selection Payment Confirmation Valid dates Invalid return date No flights found API API API API
  15. Buying a flight ticket We must make sure each API

    is self-tested e2e: buy a round-trip flight Search Flight selection Payment Confirmation Select valid dates API API API API Select a flight with seats available Make a payment with valid data Successful notification E2E Scenario
  16. How can test projects be created?

  17. Model 1 A test project for all microservices BACKEND TEST

    TEST PROJECT
  18. Model 1 Pros • Centralization of code in a single

    project • Speed and agility in creating tests and solving problems Cons • Constant changes by several people can have side effects on results
  19. Model 2 A test project for each microservice where interactions

    with the endpoint (s) will be in the test project. BACKEND TEST TEST TEST TEST PROJECT
  20. Model 2 Pros • Organized decentralization of test projects towards

    an API • Isolation between APIs Cons • Possible code duplication
  21. Model 3 A test project for each microservice divided into

    client and test projects BACKEND TEST PROJECT TEST TEST TEST CLIENT CLIENT CLIENT
  22. Model 3 Client project We will put here all the

    necessary logic to make the requests as: ◦ Exception return ◦ Transport Objects ◦ Request call ◦ Customizations for validations ◦ Pointing settings (URI, base path, port)
  23. Model 3 Test Project We will put here all the

    methods of using the API we created in the client project, creating the testing logic and validating the results. In summary, all tests are created here!
  24. Model 3 Pros • Greater version management (new features, breaking

    changes) • Easy use by other teams ◦ they just need to consume the customer and create their tests Cons • Time increase compared to previous models
  25. Implementation exemple

  26. Implementation example Project separation BACKEND TEST PROJECT TEST TEST TEST

    CLIENT CLIENT CLIENT COMMONS PARENT
  27. Project separation CLIENT TEST COMMONS PARENT Project containing all calls

    to the microservice, whether the calls were successful or simulating exceptions. Project containing tests for the microservice, testing its functionality and dependencies with other microservices. Code and libraries common to clients such as URL definitions, authentication, and any other shared code. Code and libraries common to tests such as testing data, support functions, or any common code related to tests.
  28. Microservice examples Possible graphical interface: Constraint check by CPF We

    should inform a CPF * Its a Brazilian social security number If a restriction is found, show a message
  29. Microservice examples Possible graphical interface: Loan Simulation Fill in loan

    information
  30. Microservice examples We will put here all the necessary logic

    to make the requests as: RESTRICTIONS GET /api/v1/restricrions/{cpf} GET /api/v2/restricrions/{cpf} Constraint Query API SIMULATIONS GET /api/v1/simulations/ GET /api/v1/simulations/{cpf} POST /api/v1/simulations/ PUT /api/v1/simulations/{cpf} DELETE /api/v1/simulations/{cpf} Credit Simulation API
  31. Client’s implementation Methods will be created to simulate all possible

    calls from each HTTP method CLIENT RESTRICTIONS GET /api/v1/restricrions/{cpf} Constaint Query API Client Method - find CPF Method - find CPF and return an exception
  32. CLIENT SIMULATIONS GET /api/v1/simulations/ GET /api/v1/simulations/{cpf} POST /api/v1/simulations/ Credit Simulation

    Client API Method – find all simulations Method – find a simulation by a given CPF Method – find a simulation by a given CPF and return not found Method – submit a simulation Method – submit a simulation and return unprocessable entity Method – submit a simulation and return conflict Methods will be created to simulate all possible calls from each HTTP method Client’s implementation
  33. CLIENT SIMULATIONS POST /api/v1/simulations/ Credit Simulation Client API Method –

    submit a simulation A test method will be created for one or more use of the methods on the client Test implementation TEST SIMULATIONS should create a successful simulation - Test Credit Simulation Test Project
  34. CLIENT SIMULATIONS POST /api/v1/simulations/ Method – submit a simulation and

    return unprocessable entity A test method will be created for one or more use of the methods on the client TEST SIMULATIONS should show an error regarding an attribute not sent in the request - Test - Test Credit Simulation Client API Credit Simulation Test Project Test implementation Method – submit a simulation should create a successful simulation
  35. CLIENT SIMULATIONS POST /api/v1/simulations/ Method – submit a simulation and

    return conflict TEST SIMULATIONS should show conflict when CPF already exists - Test Credit Simulation Client API Credit Simulation Test Project A test method will be created for one or more use of the methods on the client Test implementation Method – submit a simulation and return unprocessable entity should show an error regarding an attribute not sent in the request - Test - Test Method – submit a simulation should create a successful simulation
  36. How to use client <-> test?

  37. How to use client <-> test? Through the client version

    • We must add the client dependency in the test <dependency> <groupId>com.eliasnogueira</groupId> <artifactId>simulations-client</artifactId> <version>1.2.5</version> </dependency> "devDependencies": { "@eliasnogueira/simulations-client": ”1.2.5", } Java + Maven example Typescript + Node example
  38. How to use client <-> test? Pros: association of the

    client with the microservice version Just as the microservice evolves the client and the test evolve. Adding a changelog with the association of the client version with the microservice version can help fix bugs. Also tags helps if you would like to track the evolution.
  39. What can be improved

  40. What can be improved? • All the test presented in

    the *-test project could be moved to the integration layer ◦ they will provide you faster feedback • The *-test projects must have the functional/e2e tests using different APIs we depends on
  41. What can be improved? Continuous Delivery API approach build unit

    tests integration tests e2e API tests local release release/deploy Sift-Left Testing applied https://speakerdeck.com/eliasnogueira/technical-aspects-of-implementing-the-shift-left-approach
  42. Recap

  43. Recap • We’ve created a robust model for ◦ test

    a microservice in isolation (functional test) ◦ test a microservice and its dependencies (e2e) • We’ve modularized the creation of projects ◦ client: the entire API call for a microservice ◦ test: test project using the microservice client ◦ commons: client codes and libraries ◦ parent: test code and libraries
  44. Thank you! SCAN ME You can follow me on Twitter

    @eliasnogueira and find the practical examples of this presentation. Be sure to simulate the examples in the code!
  45. Projects • https://github.com/eliasnogueira/test-parent • https://github.com/eliasnogueira/test-commons • https://github.com/eliasnogueira/restrictions-client • https://github.com/eliasnogueira/restrictions-test •

    https://github.com/eliasnogueira/simulations-client • https://github.com/eliasnogueira/simulations-test
  46. Important note To be able to run the Project locally,

    after you clone it, you must configure the GitHub Packages in your pom.xml file. You can find the example here: https://docs.github.com/en/packages/working-with-a-github- packages-registry/working-with-the-apache-maven-registry Replace the OWNER by eliasnogueira