IDEA Groovy test class already exists

Question

IDEA is giving my groovy class the warning `class "MyClassTest" already exists in "my.class.package". It also doesn't seem to be doing a very good job of keeping the class updated when I run the test. I'll add an assertion guaranteed to fail, or succeed and it won't recognize it until later (later so far seems arbitrary). Given that I have maven tests passing and running correctly I suspect this is simply an IDEA configuration problem

here's my pom.xml

<?xml version="1.0" encoding="UTF-8"?>
 <project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://maven.apache.org/POM/4.0.0"
     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.xenoterracide</groupId>
<artifactId>rpf</artifactId>
<version>0.1.0</version>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.1.9.RELEASE</version>
</parent>

<build>
    <plugins>
        <plugin>
            <groupId>org.codehaus.gmavenplus</groupId>
            <artifactId>gmavenplus-plugin</artifactId>
            <version>1.2</version>
            <executions>
                <execution>
                    <goals>
                        <goal>addSources</goal>
                        <goal>addTestSources</goal>
                        <goal>generateStubs</goal>
                        <goal>compile</goal>
                        <goal>testGenerateStubs</goal>
                        <goal>testCompile</goal>
                        <goal>removeStubs</goal>
                        <goal>removeTestStubs</goal>
                    </goals>
                </execution>

            </executions>
            <configuration>
                <testSources>
                    <testSource>
                        <directory>${project.basedir}/src/test/groovy</directory>
                        <includes>
                            <include>**/*.groovy</include>
                        </includes>
                    </testSource>
                </testSources>
            </configuration>
        </plugin>
    </plugins>
</build>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-rest</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.data</groupId>
        <artifactId>spring-data-jpa</artifactId>
        <version>1.8.0.DATAJPA-622-SNAPSHOT</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-logging</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
    </dependency>
    <!--
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-security</artifactId>
    </dependency>
    -->
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.postgresql</groupId>
        <artifactId>postgresql</artifactId>
        <version>9.3-1102-jdbc41</version>
    </dependency>
    <dependency>
        <groupId>javax.enterprise</groupId>
        <artifactId>cdi-api</artifactId>
        <version>1.2</version>
    </dependency>
    <dependency>
        <groupId>org.codehaus.groovy</groupId>
        <artifactId>groovy-all</artifactId>
        <version>2.3.7</version>
        <scope>test</scope>
    </dependency>
</dependencies>

<properties>
    <!-- use UTF-8 for everything -->
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <start-class>com.xenoterracide.rpf.Application</start-class>
    <java.version>1.8</java.version>
</properties>


<repositories>
    <repository>
        <id>spring-snapshots</id>
        <name>Spring Snapshots</name>
        <url>http://repo.spring.io/snapshot</url>
        <snapshots>
            <enabled>true</enabled>
        </snapshots>
    </repository>
    <repository>
        <id>spring-releases</id>
        <url>http://repo.spring.io/libs-release</url>
    </repository>
    <repository>
        <id>spring-milestones</id>
        <name>Spring Milestones</name>
        <url>http://repo.spring.io/milestone</url>
        <snapshots>
            <enabled>false</enabled>
        </snapshots>
    </repository>
</repositories>

<pluginRepositories>
    <pluginRepository>
        <id>spring-releases</id>
        <url>http://repo.spring.io/libs-release</url>
    </pluginRepository>
</pluginRepositories>

</project>

Answer 1

I've fixed the issue by marking the target folder of the artifact as "Excluded".

I think the duplication is caused by the stub files generated in target/generated-sources/groovy-stubs. IDEA must be too curious about these files and might add them to the source set.