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In this tutorial, we’ll build a Maven multi-module project<\/a>. In this project, the services and controllers will be in different modules. Then, we’ll write some tests and use Jacoco<\/a> to calculate the code coverage.<\/p>\n First, let’s create the service layer of our multi-module application.<\/p>\n We’ll create our service and add a couple of methods:<\/strong><\/p>\n As their names indicate:<\/p>\n Let’s now write the corresponding unit tests:<\/strong><\/p>\n The tests are simply checking that the method’s output is as expected.<\/p>\n We’ll use the Maven Surefire plugin<\/a> to run the unit tests.<\/strong> Let’s configure it inside the service’s module pom.xml<\/em>:<\/p>\n We’ll now add a controller layer in our multi-module application.<\/p>\n Let’s add the controller class:<\/p>\n The fullyTested()<\/em> and indirectlyTestingServiceMethod()<\/em> methods will be tested by integration tests. As a result, those tests will cover the two service methods coveredByUnitAndIntegrationTests()<\/em> and coveredByIntegrationTest()<\/em><\/strong>. On the other hand, we’ll write no test for notTested()<\/em>.<\/p>\n We can now test our RestController<\/em><\/a>:<\/strong><\/p>\n In these tests, we start an application server and send it requests. Then, we check that the output is correct.<\/p>\n We’ll use the Maven Failsafe plugin<\/a> to run the integration tests.<\/strong> The last step is to configure it inside the controller’s module pom.xml<\/em>:<\/p>\n Jacoco (Java Code Coverage) is a tool used in Java applications to measure code coverage during testing. Let’s now compute our coverage report.<\/p>\n The prepare-agent<\/em> phase sets up the necessary hooks and configuration so that Jacoco can track the executed code while running tests<\/span>.<\/strong> This configuration is required before we run any tests. Thus, we’ll add the preparation step directly to the parent pom.xml<\/em>:<\/p>\n To gather the test coverage, we’ll create a new module aggregate-report<\/em>. It contains only a pom.xml<\/em> and has dependencies on the two previous modules.<\/p>\n Thanks to the preparation phase, we can aggregate the reports from every module. It’s the job of the report-aggregate<\/em> goal<\/a>:<\/strong><\/p>\n We can now run the verify<\/em> goal from the parent module:<\/p>\n At the end of the build, we can see that Jacoco generates the report in the target\/site\/jacoco-aggregate<\/em> folder of the aggregate-report<\/em> submodule.<\/p>\n Let’s open the index.html<\/em> file to have a look at the results.<\/p>\n To begin, we can navigate to the report for the controller class:<\/p>\n As expected, the constructor and the fullyTested()<\/em> and indirectlyTestingServiceMethod()<\/em> methods are covered by the tests, whereas notTested()<\/em> isn’t covered.<\/p>\n Let’s now have a look at the report for the service class:<\/p>\n This time, let’s focus on the coveredByIntegrationTest()<\/em> method. As we know, no test in the service module tests this method. The only test that passes through this method’s code is inside the controller module. However, Jacoco recognized that there is a test for this method. In this case, the word aggregation takes its whole meaning!<\/p>\n In this article, we created a multi-module project and gathered the test coverage thanks to Jacoco.<\/p>\n Let’s recall that we need to run the preparation phase before the tests, while the aggregation takes place after them. To go further, we can use a tool like SonarQube<\/a> to get a nice overview of the coverage result.<\/p>\n As always, the code is available over on GitHub<\/a>.<\/p>\n <\/a><\/p>\n <\/p><\/div>\n\n Learn how to build a Maven multi-module project with Jacoco coverage.<\/p>\n2. Service Layer<\/h2>\n
<\/div>\n2.1. Service Class<\/h3>\n
<\/div>\n@Service\r\nclass MyService {\r\n String unitTestedOnly() {\r\n return "unit tested only";\r\n }\r\n String coveredByUnitAndIntegrationTests() {\r\n return "covered by unit and integration tests";\r\n }\r\n String coveredByIntegrationTest() {\r\n return "covered by integration test";\r\n }\r\n String notTested() {\r\n return "not tested";\r\n }\r\n}<\/code><\/pre>\n\n
2.2. Unit Tests<\/h3>\n
<\/div>\nclass MyServiceUnitTest {\r\n MyService myService = new MyService();\r\n \r\n @Test\r\n void whenUnitTestedOnly_thenCorrectText() {\r\n assertEquals("unit tested only", myService.unitTestedOnly());\r\n }\r\n @Test\r\n void whenTestedMethod_thenCorrectText() {\r\n assertEquals("covered by unit and integration tests", myService.coveredByUnitAndIntegrationTests());\r\n }\r\n}<\/code><\/pre>\n2.3. Surefire Plugin Configuration<\/h3>\n
<\/div>\n<plugins>\r\n <plugin>\r\n <groupId>org.apache.maven.plugins<\/groupId>\r\n <artifactId>maven-surefire-plugin<\/artifactId>\r\n <version>3.1.2<\/version>\r\n <configuration>\r\n <includes>\r\n <include>**\/*Test.java<\/include>\r\n <\/includes>\r\n <\/configuration>\r\n <\/plugin>\r\n<\/plugins><\/code><\/pre>\n3. Controller Layer<\/h2>\n
<\/div>\n3.1. Controller Class<\/h3>\n
<\/div>\n@RestController\r\nclass MyController {\r\n private final MyService myService;\r\n public MyController(MyService myService) {\r\n this.myService = myService;\r\n }\r\n @GetMapping("\/tested")\r\n String fullyTested() {\r\n return myService.coveredByUnitAndIntegrationTests();\r\n }\r\n @GetMapping("\/indirecttest")\r\n String indirectlyTestingServiceMethod() {\r\n return myService.coveredByIntegrationTest();\r\n }\r\n @GetMapping("\/nottested")\r\n String notTested() {\r\n return myService.notTested();\r\n }\r\n}<\/code><\/pre>\n3.2. Integration Tests<\/h3>\n
<\/div>\n@SpringBootTest(classes = MyApplication.class)\r\n@AutoConfigureMockMvc\r\nclass MyControllerIntegrationTest {\r\n @Autowired\r\n private MockMvc mockMvc;\r\n @Test\r\n void whenFullyTested_ThenCorrectText() throws Exception {\r\n mockMvc.perform(MockMvcRequestBuilders.get("\/tested"))\r\n .andExpect(MockMvcResultMatchers.status()\r\n .isOk())\r\n .andExpect(MockMvcResultMatchers.content()\r\n .string("covered by unit and integration tests"));\r\n }\r\n @Test\r\n void whenIndirectlyTestingServiceMethod_ThenCorrectText() throws Exception {\r\n mockMvc.perform(MockMvcRequestBuilders.get("\/indirecttest"))\r\n .andExpect(MockMvcResultMatchers.status()\r\n .isOk())\r\n .andExpect(MockMvcResultMatchers.content()\r\n .string("covered by integration test"));\r\n }\r\n}<\/code><\/pre>\n3.3. Failsafe Plugin Configuration<\/h3>\n
<\/div>\n<plugin>\r\n <groupId>org.apache.maven.plugins<\/groupId>\r\n <artifactId>maven-failsafe-plugin<\/artifactId>\r\n <version>3.1.2<\/version>\r\n <executions>\r\n <execution>\r\n <goals>\r\n <goal>integration-test<\/goal>\r\n <goal>verify<\/goal>\r\n <\/goals>\r\n\t<\/execution>\r\n <\/executions>\r\n <configuration>\r\n <includes>\r\n <include>**\/*IntegrationTest.java<\/include>\r\n <\/includes>\r\n <\/configuration>\r\n<\/plugin><\/code><\/pre>\n4. Aggregating Coverage via Jacoco<\/h2>\n
<\/div>\n4.1. Preparing Jacoco Agent<\/h3>\n
<\/div>\n<plugin>\r\n <groupId>org.jacoco<\/groupId>\r\n <artifactId>jacoco-maven-plugin<\/artifactId>\r\n <version>0.8.8<\/version>\r\n <executions>\r\n <execution>\r\n <goals>\r\n <goal>prepare-agent<\/goal>\r\n <\/goals>\r\n <\/execution>\r\n <\/executions>\r\n<\/plugin><\/code><\/pre>\n4.2. Gathering Tests Results<\/h3>\n
<\/div>\n<plugin>\r\n <groupId>org.jacoco<\/groupId>\r\n <artifactId>jacoco-maven-plugin<\/artifactId>\r\n <version>0.8.8<\/version>\r\n <executions>\r\n <execution>\r\n <phase>verify<\/phase>\r\n <goals>\r\n <goal>report-aggregate<\/goal>\r\n <\/goals>\r\n <configuration>\r\n <dataFileIncludes>\r\n <dataFileInclude>**\/jacoco.exec<\/dataFileInclude>\r\n <\/dataFileIncludes>\r\n <outputDirectory>${project.reporting.outputDirectory}\/jacoco-aggregate<\/outputDirectory>\r\n <\/configuration>\r\n <\/execution>\r\n <\/executions>\r\n<\/plugin><\/code><\/pre>\n$ mvn clean verify<\/code><\/pre>\n![\"\"](\"https:\/\/www.baeldung.com\/wp-content\/uploads\/2023\/09\/controller_coverage-300x55.png\")
<\/a><\/p>\n![\"\"](\"https:\/\/www.baeldung.com\/wp-content\/uploads\/2023\/09\/service_coverage-300x60.png\")
<\/a><\/p>\n5. Conclusion<\/h2>\n
<\/div>\n<\/p>\n
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