Java – How to make Maven unit test code coverage work

jacocojavamavenunit testing

In Eclipse, I have used EcLEmma to see the unit test code coverage. Which worked fine.
Therefore I have tried to use the JaCoCo plugin for Maven to see the same report with Surefire from Maven build, or even better, with a certain profile, or in the site cycle. Without success. All suggested solutions here didn't work for me.

What is the best way to get a unit test code coverage report (with surefire)?

[Edit]
to be more specific why jacoco failed for me…. as I got always the
Skipping JaCoCo execution due to missing execution data

from the pom
in the properties

    <jacoco.it.execution.data.file>${project.build.directory}/coverage-reports/jacoco-it.exec</jacoco.it.execution.data.file>
    <jacoco.ut.execution.data.file>${project.build.directory}/coverage-reports/jacoco-ut.exec</jacoco.ut.execution.data.file>

in the Build section

        <pluginManagement>
        <plugins>
            <plugin>
                <groupId>org.eclipse.m2e</groupId>
                <artifactId>lifecycle-mapping</artifactId>
                <version>1.0.0</version>
                <configuration>
                    <lifecycleMappingMetadata>
                        <pluginExecutions>
                            <pluginExecution>
                                <pluginExecutionFilter>
                                    <groupId>org.jacoco</groupId>
                                    <artifactId>jacoco-maven-plugin</artifactId>
                                    <versionRange>${jacoco.version}</versionRange>
                                    <executions>
                                        <!-- Prepares the property pointing to the JaCoCo runtime agent 
                                            which is passed as VM argument when Maven the Surefire plugin is executed. -->
                                        <execution>
                                            <id>pre-unit-test</id>
                                            <goals>
                                                <goal>prepare-agent</goal>
                                            </goals>
                                            <configuration>
                                                <!-- Sets the path to the file which contains the execution 
                                                    data. -->
                                                <destFile>${jacoco.ut.execution.data.file}</destFile>
                                                <!-- Sets the name of the property containing the settings for 
                                                    JaCoCo runtime agent. -->
                                                <propertyName>surefireArgLine</propertyName>
                                            </configuration>
                                        </execution>
                                        <!-- Ensures that the code coverage report for unit tests is created 
                                            after unit tests have been run. -->
                                        <execution>
                                            <id>post-unit-test</id>
                                            <phase>test</phase>
                                            <goals>
                                                <goal>report</goal>
                                            </goals>
                                            <configuration>
                                                <!-- Sets the path to the file which contains the execution 
                                                    data. -->
                                                <dataFile>${jacoco.ut.execution.data.file}</dataFile>
                                                <!-- Sets the output directory for the code coverage report. -->
                                                <outputDirectory>${project.reporting.outputDirectory}/jacoco-ut</outputDirectory>
                                            </configuration>
                                        </execution>
                                        <!-- Prepares the property pointing to the JaCoCo runtime agent 
                                            which is passed as VM argument when Maven the Failsafe plugin is executed. -->
                                        <execution>
                                            <id>pre-integration-test</id>
                                            <phase>pre-integration-test</phase>
                                            <goals>
                                                <goal>prepare-agent</goal>
                                            </goals>
                                            <configuration>
                                                <!-- Sets the path to the file which contains the execution 
                                                    data. -->
                                                <destFile>${jacoco.it.execution.data.file}</destFile>
                                                <!-- Sets the name of the property containing the settings for 
                                                    JaCoCo runtime agent. -->
                                                <propertyName>failsafeArgLine</propertyName>
                                            </configuration>
                                        </execution>
                                        <!-- Ensures that the code coverage report for integration tests 
                                            after integration tests have been run. -->
                                        <execution>
                                            <id>post-integration-test</id>
                                            <phase>post-integration-test</phase>
                                            <goals>
                                                <goal>report</goal>
                                            </goals>
                                            <configuration>
                                                <!-- Sets the path to the file which contains the execution 
                                                    data. -->
                                                <dataFile>${jacoco.it.execution.data.file}</dataFile>
                                                <!-- Sets the output directory for the code coverage report. -->
                                                <outputDirectory>${project.reporting.outputDirectory}/jacoco-it</outputDirectory>
                                            </configuration>
                                        </execution>
                                    </executions>
                                </pluginExecutionFilter>
                            </pluginExecution>
                        </pluginExecutions>
                    </lifecycleMappingMetadata>
                </configuration>
            </plugin>
        </plugins>
    </pluginManagement>

was my last try but the pom becomes bigger and bigger without any result

which failes with

configuring report plugin org.apache.maven.plugins:maven-jxr-plugin:2.3

configuring report plugin org.jacoco:jacoco-maven-plugin:0.7.5.201505241946

Skipping JaCoCo execution due to missing execution data file:……\target\jacoco.exec

Skipping JaCoCo execution due to missing execution data file:……\target\jacoco-it.exec

…. => long project path

Best Answer

Thanks user3732793

Personnaly, I only needed to add this to my pom.xml

<project>
...

    <dependencies>
        ...
    </dependencies>

    <build>
        <plugins>
            ...
            <!-- Code Coverage report generation -->
            <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>0.7.9</version>
                <executions>
                    <execution>
                        <goals>
                            <goal>prepare-agent</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>generate-code-coverage-report</id>
                        <phase>test</phase>
                        <goals>
                            <goal>report</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

Then I am running

mvn test

and I get the HTML report under ./target/site/jacoco/*.html

Related Solutions

How should I unit test multithreaded code

Look, there's no easy way to do this. I'm working on a project that is inherently multithreaded. Events come in from the operating system and I have to process them concurrently.

The simplest way to deal with testing complex, multithreaded application code is this: If it's too complex to test, you're doing it wrong. If you have a single instance that has multiple threads acting upon it, and you can't test situations where these threads step all over each other, then your design needs to be redone. It's both as simple and as complex as this.

There are many ways to program for multithreading that avoids threads running through instances at the same time. The simplest is to make all your objects immutable. Of course, that's not usually possible. So you have to identify those places in your design where threads interact with the same instance and reduce the number of those places. By doing this, you isolate a few classes where multithreading actually occurs, reducing the overall complexity of testing your system.

But you have to realize that even by doing this, you still can't test every situation where two threads step on each other. To do that, you'd have to run two threads concurrently in the same test, then control exactly what lines they are executing at any given moment. The best you can do is simulate this situation. But this might require you to code specifically for testing, and that's at best a half step towards a true solution.

Probably the best way to test code for threading issues is through static analysis of the code. If your threaded code doesn't follow a finite set of thread safe patterns, then you might have a problem. I believe Code Analysis in VS does contain some knowledge of threading, but probably not much.

Look, as things stand currently (and probably will stand for a good time to come), the best way to test multithreaded apps is to reduce the complexity of threaded code as much as possible. Minimize areas where threads interact, test as best as possible, and use code analysis to identify danger areas.

Java – How to test a class that has private methods, fields or inner classes

Update:

Some 10 years later perhaps the best way to test a private method, or any inaccessible member, is via @Jailbreak from the Manifold framework.
@Jailbreak Foo foo = new Foo();
// Direct, *type-safe* access to *all* foo's members
foo.privateMethod(x, y, z);
foo.privateField = value;
This way your code remains type-safe and readable. No design compromises, no overexposing methods and fields for the sake of tests.

If you have somewhat of a legacy Java application, and you're not allowed to change the visibility of your methods, the best way to test private methods is to use reflection.

Internally we're using helpers to get/set private and private static variables as well as invoke private and private static methods. The following patterns will let you do pretty much anything related to the private methods and fields. Of course, you can't change private static final variables through reflection.

Method method = TargetClass.getDeclaredMethod(methodName, argClasses);
method.setAccessible(true);
return method.invoke(targetObject, argObjects);

And for fields:

Field field = TargetClass.getDeclaredField(fieldName);
field.setAccessible(true);
field.set(object, value);

Notes:
1. TargetClass.getDeclaredMethod(methodName, argClasses) lets you look into private methods. The same thing applies for getDeclaredField.
2. The setAccessible(true) is required to play around with privates.

Best Answer

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Java – How to test a class that has private methods, fields or inner classes

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