How to generate a SINGLE jar contains /src/main/java and /src/test/java - maven

Question

I have created a maven project and trying to generate a SINGLE jar file should contain both /src/main/java & /src/test/java.
But it is generating two SEPARATE jar files. Please let me know, how can I achieve this in maven?
generated jar files:
test-0.0.1-SNAPSHOT.jar
test-0.0.1-SNAPSHOT-tests.jar
my pom.xml:
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.testmaven</groupId>
<artifactId>test</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>
<name>test</name>
<url>http://maven.apache.org</url>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.2.0</version>
<executions>
<execution>
<goals>
<goal>test-jar</goal>
</goals>
</execution>
</executions>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>3.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>

Answer 1

You cannot access test classes from application code. So no maven plugin will help you to add src/main/java and src/test/java in a single executable jar.
If at all you want to access the main classes from the test project, check the answer similar to your question on stackoverflow here:
How can I include test classes into Maven jar and execute them?

Answer 2

I have tried with below approach and it worked.
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>1.9.1</version>
<executions>
<execution>
<id>add-source</id>
<phase>generate-sources</phase>
<goals>
<goal>add-source</goal>
</goals>
<configuration>
<sources>
<source>${project.basedir}/src/test/java/</source>
</sources>
</configuration>
</execution>
</executions>