How to execute JUnit and TestNG tests in same project using maven-surefire-plugin?

Official way with selecting providers.

You can also specify multiple providers as dependencies, and they will all be run and produce a common report. This may be especially handy with external providers, since there are few use-cases for combining the included providers.

<plugin>
    <artifactId>maven-surefire-plugin</artifactId>
    <version>2.18.1</version>
    <dependencies>
        <dependency>
            <groupId>org.apache.maven.surefire</groupId>
            <artifactId>surefire-junit47</artifactId>
            <version>2.18.1</version>
        </dependency>
        <dependency>
            <groupId>org.apache.maven.surefire</groupId>
            <artifactId>surefire-testng</artifactId>
            <version>2.18.1</version>
        </dependency>
    </dependencies>
</plugin>

More info about this: Mixing TestNG and JUnit tests in one Maven module – 2013 edition

Current Link for this in the maven-surefire-plugin examples. Search for "Running TestNG and JUnit Tests".

You will want to configure the testng provider to ignore the junit tests like so:

<plugin>
    <artifactId>maven-surefire-plugin</artifactId>
    <version>2.18.1</version>
    <configuration>        
    <properties>
        <property>
            <name>junit</name>
            <value>false</value>
         </property>
    </properties>        
    </configuration>
    [...providers as dependecies, see above...]
</plugin>

I have a better solution.

The idea is to create two executions of the maven-surefire-plugin, one for JUnit, one for TestNG. You can disable one of TestNG or JUnit per execution by specifying nonexisting junitArtifactName or testNGArtifactName:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <executions>
        <execution>
            <phase>test</phase>
            <goals>
                <goal>test</goal>
            </goals>
            <configuration> 
                <testNGArtifactName>none:none</testNGArtifactName>
            </configuration>
        </execution>
        <execution>
            <id>test-testng</id>
            <phase>test</phase>
            <goals>
                <goal>test</goal>
            </goals>
            <configuration> 
                <junitArtifactName>none:none</junitArtifactName>
            </configuration>
        </execution>
    </executions>
</plugin>

There is an open issue for this, so there's no elegant way to do this.

It would be far simpler for you to pick a framework and stick with it.

Edit: My previous answer doesn't work because you can't specify dependencies in the execution. I've tried a few approaches, but the best I can manage is to create a profile for the TestNG dependency so you can toggle between TestNG and JUnit testing, there doesn't seem to be a means to run both TestNG and Junit 4 tests.

One other point to note: You can launch your JUnit tests from TestNG, but I think this only works for JUnit 3 tests.