Error when running a GWTTestCase using maven gwt plugin

Question

I've created a test which extends GWTTestCase but I'm getting this error:

mvn integration-test gwt:test
...
Running com.myproject.test.ui.GwtTestMyFirstTestCase
Translatable source found in...                       
[WARN] No source path entries; expect subsequent failures
[ERROR] Unable to find type 'java.lang.Object'
[ERROR] Hint: Check that your module inherits 'com.google.gwt.core.Core' either directly or indirectly (most often by inheriting module 'com.google.gwt.user.User')
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 2.1 sec <<< FAILURE!

GwtTestMyFirstTestCase.java is in /src/test/java, while the GWT module is located in src/main/java. I assume this shouldn't be a problem.

I've done everything required according to http://mojo.codehaus.org/gwt-maven-plugin/user-guide/testing.html and of course that my gwt module already has com.google.gwt.core.Core indirectly imported.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.myproject</groupId>
<artifactId>main</artifactId>
<packaging>jar</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>Main Module</name>

<properties>
    <gwt.module>com.myproject.MainModule</gwt.module>
</properties>

<parent>
    <groupId>com.myproject</groupId>
    <artifactId>app</artifactId>
    <version>0.1.0-SNAPSHOT</version>
</parent>

<dependencies>

    <dependency>
        <groupId>com.myproject</groupId>
        <artifactId>app-commons</artifactId>
        <version>0.0.1-SNAPSHOT</version>
    </dependency>

    <dependency>
        <groupId>com.google.gwt</groupId>
        <artifactId>gwt-dev</artifactId>
        <version>${gwt.version}</version>
        <scope>provided</scope>
    </dependency>


</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-dependency-plugin</artifactId>
            <configuration>
                <outputFile>../app/src/main/webapp/WEB-INF/main.tree</outputFile>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>gwt-maven-plugin</artifactId>


            <executions>
                    <execution>
                        <goals>
                            <goal>test</goal>
                        </goals>
                    </execution>
            </executions>

        </plugin>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-jar-plugin</artifactId>
            <configuration>
                <classesDirectory>
                    ${project.build.directory}/${project.build.finalName}/${gwt.module}
                </classesDirectory>
            </configuration>
        </plugin>
    </plugins>
</build>

</project>

Here is the test case, located in /src/test/java/com/myproject/test/ui

public class GwtTestMyFirstTestCase extends GWTTestCase {

    @Override
    public String getModuleName() {
        return "com.myproject.MainModule";
    }

    public void testSomething() {


    }

}

Here is the gwt module I'm trying to test, located in src/main/java/com/myproject/MainModule.gwt.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE module PUBLIC "-//Google Inc.//DTD Google Web Toolkit 1.7.1//EN" "http://google-web-toolkit.googlecode.com/svn/tags/1.7.1/distro-source/core/src/gwt-module.dtd">
<module>

    <inherits name='com.myproject.Commons' />

    <source path="site" />

    <source path="com.myproject.test.ui" />

    <set-property name="gwt.suppressNonStaticFinalFieldWarnings" value="true" />

    <entry-point class='com.myproject.site.SiteModuleEntry' />
</module>

Can anyone give me a hint or two about what I'm doing wrong?

Answer 1

To reproduce the solution used by KevinWong from the maven-gwt-plugin doc, which worked for me after losing over an hour trying the other solutions.

<plugin>
    <artifactId>maven-surefire-plugin</artifactId>
    <version>2.6</version>
    <configuration>
      <additionalClasspathElements>
        <additionalClasspathElement>${project.build.sourceDirectory}</additionalClasspathElement>
        <additionalClasspathElement>${project.build.testSourceDirectory}</additionalClasspathElement>
      </additionalClasspathElements>
      <useManifestOnlyJar>false</useManifestOnlyJar>
      <forkMode>always</forkMode>
      <systemProperties>
        <property>
          <name>gwt.args</name>
          <value>-out \${webAppDirectory}</value>
        </property>
      </systemProperties>
    </configuration>
  </plugin>