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>