I had the same problem, and it took me a while to figure out. My setup was pulling in an older version of jboss.javassist, which oddly was preventing the PowerMockRunner from working at all.
It's worth noting that I also have a mixed JUnit / TestNG environment. I previously tried the solution of adding multiple surefire providers, and that didn't work either (using surefire 2.14.1). After upgrading to surefire 2.17, both my JUnit and TestNG tests started running without needing to declare any surefire providers. In fact, the JUnit provider threw an error for me, because I'm using groups. Apparently the TestNG provider allows free-form text (e.g. "integration") while the JUnit provider expects a classpath (e.g. "com.example.UnitTests").
Here's my plugin section...
<plugin>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.17</version>
<configuration>
<groups>spring, unit, integration</groups>
<systemPropertyVariables>
<java.awt.headless>true</java.awt.headless>
<org.apache.activemq.default.directory.prefix>target/test/</org.apache.activemq.default.directory.prefix>
<log4j.configuration>file:${project.basedir}/src/test/resources/log4j.properties</log4j.configuration>
</systemPropertyVariables>
<argLine>${surefire.args}</argLine>
</configuration>
</plugin>
... and the relevant testing deps ...
<dependency>
<groupId>org.mockito</groupId>
<artifactId>mockito-all</artifactId>
<version>1.9.5</version>
<scope>test</scope>
</dependency>
<!--
PowerMock versions are compatible with specific Mockito versions.
https://code.google.com/p/powermock/wiki/MockitoUsage13
-->
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-module-junit4</artifactId>
<version>1.5.4</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.powermock</groupId>
<artifactId>powermock-api-mockito</artifactId>
<version>1.5.4</version>
<scope>test</scope>
</dependency>
<!-- without this PowerMock tests don't run in maven -->
<dependency>
<groupId>jboss</groupId>
<artifactId>javassist</artifactId>
<version>3.8.0.GA</version>
<scope>test</scope>
</dependency>