a Spring framework for Consumer Driven Contracts (CDC)

Producer Setup

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Dependencies

		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-contract-verifier</artifactId>
			<scope>test</scope>
		</dependency>

Plugins

			<plugin>
				<groupId>org.springframework.cloud</groupId>
				<artifactId>spring-cloud-contract-maven-plugin</artifactId>
				<version>3.1.3</version>
				<extensions>true</extensions>
				<configuration>
					<testFramework>JUNIT5</testFramework>
					<baseClassForTests>
						com.example.demo.BaseTestClass
					</baseClassForTests>
				</configuration>
			</plugin>

Source Code

@RestController
public class DefaultController {

    @GetMapping("/validate/prime-number")
    public String isNumberPrime(@RequestParam("number") Integer number) {
        return number % 2 == 0 ? "Even" : "Odd";
    }

}

Base Test Code

@DirtiesContext
@AutoConfigureMessageVerifier
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.MOCK)
public class BaseTestClass {

    @Autowired
    private DefaultController defaultController;

    @BeforeEach
    public void setup() {
        StandaloneMockMvcBuilder standaloneMockMvcBuilder = MockMvcBuilders.standaloneSetup(defaultController);
        RestAssuredMockMvc.standaloneSetup(standaloneMockMvcBuilder);
    }
}

Contract Code

test/resources/contract/shouldReturnEvenWhenRequestParamIsEven.groovy

import org.springframework.cloud.contract.spec.Contract

Contract.make {
    description "should return even when number input is even"
    request {
        method GET()
        url("/validate/prime-number") {
            queryParameters {
                parameter("number", "2")
            }
        }
    }
    response {
        body("Even")
        status 200
    }
}

Build ContractVerifierTest

mvn clean install

The plugin will auto-generate the following file target/generated-test-sources/contracts/com.example.demo/ContractVerifierTest.class

public class ContractVerifierTest extends BaseTestClass {

	@Test
	public void validate_shouldReturnEvenWhenRequestParamIsEven() throws Exception {
		// given:
			MockMvcRequestSpecification request = given();

		// when:
			ResponseOptions response = given().spec(request)
					.queryParam("number","2")
					.get("/validate/prime-number");

		// then:
			assertThat(response.statusCode()).isEqualTo(200);

		// and:
			String responseBody = response.getBody().asString();
			assertThat(responseBody).isEqualTo("Even");
	}

}

Consumer Setup

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Dependencies

		<dependency>
			<groupId>org.springframework.cloud</groupId>
			<artifactId>spring-cloud-starter-contract-stub-runner</artifactId>
			<scope>test</scope>
		</dependency>

Source Code

@Configuration
public class DefaultConfiguration {
    @Bean
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

@RestController
public class DefaultController {

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/calculate")
    public String checkOddAndEven(@RequestParam("number") Integer number) {
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.add("Content-Type", "application/json");

        ResponseEntity<String> responseEntity = restTemplate.exchange(
                "http://localhost:8090/validate/prime-number?number=" + number,
                HttpMethod.GET,
                new HttpEntity<>(httpHeaders),
                String.class);

        return responseEntity.getBody();
    }
}

Test Code

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.json.AutoConfigureJsonTesters;
import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.cloud.contract.stubrunner.spring.AutoConfigureStubRunner;
import org.springframework.cloud.contract.stubrunner.spring.StubRunnerProperties;
import org.springframework.http.MediaType;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.request.MockMvcRequestBuilders;

import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

/**
 * stubsMode = StubRunnerProperties.StubsMode.LOCAL - informs our consumer of the available stubs in our local Maven repository
 * ids - tells what groupId and artifactId of the producer stub jar
 * 8090 - the port on which the generated stubs will run
 */
@AutoConfigureMockMvc
@AutoConfigureJsonTesters
@AutoConfigureStubRunner(
        stubsMode = StubRunnerProperties.StubsMode.LOCAL,
        ids = "com.example:producer-service:+:stubs:8090")
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.MOCK)
class ContractTest {

    @Autowired
    MockMvc mockMvc;

    @Test
    void given_WhenPassEvenNumberInQueryParam_ThenReturnEven() throws Exception {
        mockMvc.perform(MockMvcRequestBuilders.get("/calculate?number=2")
                        .contentType(MediaType.APPLICATION_JSON))
                .andExpect(status().isOk())
                .andExpect(content().string("Even"));
    }
}

Test ContractVerifierTest

mvn clean package

Resources

• https://www.baeldung.com/spring-cloud-contract
• https://spring.io/projects/spring-cloud-contract
• http://antkorwin.com/cloud/spring_cloud_contract_junit5.html