Maven executes only few tests

I am struggeling on executing all junit tests by maven test. There are 57 Tests in 10 classes but somehow maven executes only 12 Tests in 6 classes. The ignored classes are in the same folder as another class, beeing executed.

However, when run my test source folter as JUnit Test it does execute all tests.

Funny thing: I copied a test, which had been executed, but even the copy is ignored by maven.

Any help will be appreciated.

<build>
    <sourceDirectory>src</sourceDirectory>
    <testSourceDirectory>test</testSourceDirectory>
    <resources>
        <resource>
            <directory>resources</directory>
            <excludes>
                <exclude>**/*.java</exclude>
            </excludes>
        </resource>
    </resources>


    <plugins>
        <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.3</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>sonar-maven-plugin</artifactId>
            <version>2.3</version>
        </plugin>
        <plugin>
            <groupId>org.jacoco</groupId>
            <artifactId>jacoco-maven-plugin</artifactId>
            <version>0.7.5.201505241946</version>
            <configuration>
                <append>true</append>
            </configuration>
            <executions>
                <execution>
                    <goals>
                        <goal>prepare-agent</goal>
                    </goals>
                </execution>
                <execution>
                    <id>post-unit-test</id>
                    <phase>test</phase>
                    <goals>
                        <goal>report</goal>
                    </goals>
                </execution>
            </executions>
        </plugin>
    </plugins>

</build>