Testing Java Microservices with Consumer-driven contracts Andrew Morgan @mogronalol
Microservices testing is hard
Consumer driven contract testing
About Me • Independent Consultant specialising in microservices & continuous delivery • PluralSight Author • InfoQ Editor Andrew Morgan @mogronalol
Agenda • Introducing microservices testing challenges • Consumer-driven contract testing overview • Following through the workflow with Spring Cloud Contract • Advanced consumer-driven contract concepts
Agenda • Introducing microservices testing challenges • Consumer-driven contract testing overview • Following through the workflow with Spring Cloud Contract • Advanced consumer-driven contract concepts
What are Microservices? Rewards Accounts Payments Loans
What are Microservices? Rewards HTTP Accounts HTTP Payments Loans
What are Microservices? Rewards HTTP Accounts Messaging HTTP Payments Loans
The root cause of testing challenges REST API Booking Payments
End-to-end Testing Microservices Automated tests Browser or other UI Environment
Disadvantages of End-to-end Testing Build time Debuggability Infrastructure cost Operations Flakiness Distributed monolith
Mocking or Stubbing Dependencies Automated tests Microservice Mock or Stub of Dependency
Disadvantages of Mocking or Stubbing False positives Staleness Difficult to maintain
The Weak Feedback Loop Run individual Build and deploy microservice Release to stage End-to-end test tests Slow and flaky False positives
Agenda • Introducing microservices testing challenges • Consumer-driven contract testing overview • Following through the workflow with Spring Cloud Contract • Advanced consumer-driven contract concepts
What is Consumer-driven Contract Testing? Fills the microservices testing gap Continuous testing against contracts Consumers drive the implementation of providers Independently testable and releasable microservices
Test Architecture Overview ??? Consumer Provider
Key Contract Characteristics An agreed interaction between microservices Continuously tested No specific protocol Not the same stubbing! Definitely not API documentation!
What is an Interaction? Scenario: Should return no flights between London and Paris
What is an Interaction? Scenario: Should return no flights between London and Paris Required Request: GET /flights?from=London&to=Paris
What is an Interaction? Scenario: Should return no flights between London and Paris Required Request: GET /flights?from=London&to=Paris Given Response: 200 []
The Consumer Side Automated Consuming Stub of provider tests Microservice microservice Generates The interaction our test depends on
The Provider Side Providing Contract verification Microservice tests Generates Pre-defined contract
The Benefits Fast and reliable feedback Less money spent on infrastructure API delivers exactly what is required Understanding dependency hell No stale stubs Easy to work in parallel
Agenda • Introducing microservices testing challenges • Consumer-driven contract testing overview • Following through the workflow with Spring Cloud Contract • Advanced consumer-driven contract concepts
Spring Cloud Contract Overview JVM-based CDC framework Spring Boot Integration Groovy Based Contract Definition Language Message-driven and HTTP-driven interactions
Credit Card Application Feature
Credit Card Application Feature JUnit Test Credit card Credit score service applications service
Credit Card Application Feature JUnit Test Credit card Credit score service applications service Applies for credit card
Credit Card Application Feature JUnit Test Credit card Credit score service applications service Calculates credit score
Credit Card Application Feature JUnit Test Credit card Credit score service applications service Accepts or rejects based on credit score
Following the CDC Workflow Write a Define Build Make Build Make tests failing test Contract stubs tests verification pass pass tests
Following the CDC Workflow Write a failing test
A Failing Test
A Failing Test
A Failing Test
Implementing Our Endpoint JUnit Test
Implementing Our Endpoint JUnit Test Credit card applications service
Implementing Our Endpoint JUnit Test Credit card Credit score service applications service Does not exist
Implementing Our Endpoint JUnit Test Credit card Credit score service applications service Fails here
Following the CDC Workflow Write a Define failing test Contract
Contract Definition Language Request made by our test Response expected by our test
Following the CDC Workflow Write a Define Build failing test Contract stubs
Stub Generation Contract Spring Cloud Stub Jar Contract Plugin
wiremock.org
Following the CDC Workflow Write a Define Build Make failing test Contract stubs tests pass
The Stub Runner Download given stubs Boots WireMock Imports stubs into Wiremock
From a Failing Test Unit test Credit card Credit score applications service service Fails here
…to a Passing Test Unit test Credit card Spring Cloud applications service Contract Stub Passes here
Following the CDC Workflow Write a Define Build Make Build failing test Contract stubs tests verification pass tests
Provider Test Generation Contract Spring Cloud Verification Contract Plugin Tests
Following the CDC Workflow Write a Define Build Make Build Make tests failing test Contract stubs tests verification pass pass tests
From Failing… Contract Verification Credit score Tests service
To Passing… Contract Verification Credit score Tests service Implement me
“Consumer-driven contracts are like TDD applied at the API level.” - Marcin Grzejszczak
Agenda • Introducing microservices testing challenges • Consumer-driven contract testing overview • Following through the workflow with Spring Cloud Contract • Advanced consumer-driven contract concepts
Does this only work with exact comparisons?
Subsets Regex XPath JSON XML Ignore casing Starts with More
What about messaging?
Message-driven CDC Consumer Provider
Message-driven CDC Consumer Broker Provider
Why Messaging? Message schemas and queues are shared Asynchronous failures are a debugging nightmare! Brokers are slow
Where do we store our contracts?
Contract Repository
Contract Repository
Talk Summary Don’t build and test microservices like a monolith Consumer-driven contracts promote independence Leverage frameworks like Spring Cloud Contract and Pact
Questions? https://www.pluralsight.com/profile/author/andrew-morgan @mogronalol
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