Build resilient systems with Spring Cloud Contract and Testcontainers

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What is going to happen?

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About Olga Senior Software Engineer in Spring Cloud Team ● Spring Cloud LoadBalancer (Spring Cloud Commons) ● Spring Interface Clients ● Spring Cloud Contract ● Spring Cloud OpenFeign ● Spring Cloud Netﬂix ● Spring Native support for Spring Cloud projects ● RSocket HTTP Bridge https://github.com/OlgaMaciaszek https://twitter.com/olga_maciaszek

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Developer advocate at AtomicJar ● Testcontainers for Java https://github.com/shelajev https://twitter.com/shelajev About Oleg

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Our project

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A new message topic: servings body: { "beverages": [ { "uuid": "16b439a4-6ace-4901-8fb6-728588c12da8", "coffee": { "name": "Latte", "coffeeContent": 60, "steamedMilkContent": 180, "milkFoamContent": 5 } } // … ] } headers: “contentType”: “application/json” “testKey1”: “testValue1”

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A new message

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We go to production! Production

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A new message topic: serving body: { "beverages": [ { "uuid": "16b439a4-6ace-4901-8fb6-728588c12da8", "coffee": { "name": "Latte", "coffeeContent": 60, "steamedMilkContent": 180, "milkFoamContent": 5 } } // … ] } headers: “contentType”: “application/json” “testKey1”: “testValue1”

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A new message topic: servings body: { "beverages": [ { "id": "16b439a4-6ace-4901-8fb6-728588c12da8", "coffee": { "name": "Latte", "coffeeContent": 60, "steamedMilkContent": 180, "milkFoamContent": 5 } } // … ] } headers: “contentType”: “application/json” “testKey1”: “testValue1”

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Stubs alone don’t guarantee ANYTHING

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The Answer: Consumer-Driven Contracts

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Spring Cloud Contract

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No free stubs! Build tool plugin Contract deﬁnitions Generated tests Stubs Test setup conﬁguration

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Producer Build Setup org.springframework.cloud spring-cloud-contract-maven-plugin 4.0.3-SNAPSHOT true JUNIT5 io.xxx.BaseTestClass org.springframework.boot spring-boot-maven-plugin

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● Setup the environment ● Create inputs ● Produce the outputs (with production code) Producer test setup

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● TC slide

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● TC slide

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No free stubs! Build tool plugin Contract deﬁnitions Generated tests Stubs Test setup conﬁguration

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Contract Contract.make { label("serving") input { triggeredBy("triggerServing()") } / ... }

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Contract Contract.make { / ... outputMessage { sentTo("servings") body([beverages: [[uuid : $(anyUuid()), coffee: [ name : "Latte", coffeeContent : "60", steamedMilkContent: "180", milkFoamContent : "5" ]]]]) / ... }

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Contract Contract.make { / ... headers { messagingContentType(applicationJson()) header 'testKey1', 'testValue1' } }

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No free stubs! Build tool plugin Contract deﬁnitions Generated tests Stubs Test setup conﬁguration

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Generated Contract Test @Test public void validate_shouldSendServing() throws Exception { // when: triggerServing(); // then: ContractVerifierMessage response = contractVerifierMessaging.receive("servings", contract(this, "shouldSendServing.yml")); assertThat(response).isNotNull(); // and: assertThat(response.getHeader("contentType")).isNotNull(); assertThat(response.getHeader("contentType").toString()).isEqualTo("application/json"); assertThat(response.getHeader("testKey1")).isNotNull(); assertThat(response.getHeader("testKey1").toString()).isEqualTo("testValue1"); // ...

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Generated Contract Test @Test public void validate_shouldSendServing() throws Exception { // ... DocumentContext parsedJson = JsonPath.parse(contractVerifierObjectMapper.writeValueAsString(response.getPayload())); assertThatJson(parsedJson).array("['beverages']").contains("['uuid']") .matches("[a-f0-9]{8}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{4}-[a-f0-9]{12}") assertThatJson(parsedJson).array("['beverages']").field("['coffee']").field("['name']") .isEqualTo("Latte"); assertThatJson(parsedJson).array("['beverages']").field("['coffee']").field("['coffeeContent'] ") .isEqualTo("60"); assertThatJson(parsedJson).array("['beverages']").field("['coffee']").field("['steamedMilkCont ent']") .isEqualTo("180"); assertThatJson(parsedJson).array("['beverages']").field("['coffee']").field("['milkFoamContent ']") .isEqualTo("5");

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No free stubs! Build tool plugin Contract deﬁnitions Generated tests Stubs Test setup conﬁguration

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Contracts vs Schemas

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Consumer integration tests using stubs from Contract and TestContainers

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Local Development Environment

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Teamwork - diﬀerent approaches Provider Contracts ● Contracts with the producer ● The producer has no knowledge of how consumers use their API ● The producer can impose contract changes on consumers Consumer Contracts ● Contracts with the consumers ● Possible issues with conﬂict resolution in case of multiple consumers ● In some implementations, the consumers can impose contract changes on the producer Consumer-Driven Contracts ● Contracts with the producer ○ If security issues, an external repo ● Consumers as key participants in the creation of the contracts ● Convenient handling of multiple consumers

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Spring Cloud Contract - Consumer-Driven Contract Flow Consumer ● Checks out Producer code repo and works locally on a contract ● Creates a pull request with the new Contract ● Collaborates with the Producer on the Contract PR ● Uses stubs published by the producer along the app for integration tests Producer ● Reviews the Contract PR ● Runs build on the PR branch (FAILURE) ● Adds required endpoints ● Runs build on the PR branch (PASSING) ● Code Deployed along with generated stubs jar

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Backward Compatibility Checks in Pipelines New API version Test with PROD contracts Deploy Test with new contracts

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Producer Build Setup - Compatibility Tests with Proﬁles apicompatibility org.springframework.cloud spring-cloud-contract-maven-plugin 4.0.3-SNAPSHOT ${repo.with.binaries} REMOTE ${project.groupId} ${project.artifactId} stubs ${latest.production.version}

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Evolving the system safely Deployment Contract ﬁelds Producer ﬁelds 0 { "uuid": "xxx" } { "uuid": "xxx" } 1 { "uuid": "xxx", "id": 5 } { "uuid": “xxx”, "id": 5 } 2 { "id": 5 } { "uuid": “xxx”, "id": 5 } 3 { "id": 5 } { "id": 5 }

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What’s next? github.com/OlgaMaciaszek/coffee testcontainers.com https://docs.spring.io/spring-cloud-contract/docs/current/reference/html/