Unable to run GWT Test (Maven)

I'm trying to run $mvn clean test for this GWT Library however it keeps on throwing this error:

[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: 10, Failures: 0, Errors: 10, Skipped: 0, Time elapsed: 12.069 sec <<< FAILURE!
testAgoHours(com.github.kevinsawicki.timeago.client.TimeAgoTest)  Time elapsed: 11.698 sec  <<< ERROR!
com.google.gwt.core.ext.UnableToCompleteException: (see previous log entries)
    at com.google.gwt.dev.cfg.ModuleDef.checkForSeedTypes(ModuleDef.java:559)
    at com.google.gwt.dev.cfg.ModuleDef.getCompilationState(ModuleDef.java:363)
    at com.google.gwt.junit.JUnitShell.runTestImpl(JUnitShell.java:1342)
    at com.google.gwt.junit.JUnitShell.runTestImpl(JUnitShell.java:1309)
    at com.google.gwt.junit.JUnitShell.runTest(JUnitShell.java:653)
    at com.google.gwt.junit.client.GWTTestCase.runTest(GWTTestCase.java:441)
    at junit.framework.TestCase.runBare(TestCase.java:134)
    at junit.framework.TestResult$1.protect(TestResult.java:110)
    at junit.framework.TestResult.runProtected(TestResult.java:128)
    at junit.framework.TestResult.run(TestResult.java:113)
    at junit.framework.TestCase.run(TestCase.java:124)
    at com.google.gwt.junit.client.GWTTestCase.run(GWTTestCase.java:296)
    at junit.framework.TestSuite.runTest(TestSuite.java:232)
    at junit.framework.TestSuite.run(TestSuite.java:227)
    at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:83)
    at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:252)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:141)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:112)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
    at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
    at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
    at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:115)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:75)

testAgoDay(com.github.kevinsawicki.timeago.client.TimeAgoTest)  Time elapsed: 0.

Correct me if I am wrong but I think the project have the correct GWT test structure. So I am not sure why it keeps throwing this error. If I run mvn gwt:test it passes but it doesn't really run any test at all.