Some tests require that the sources (gwt-dev/src, gwt-dev/test, gwt-dev/super, gwt-user/src, etc.) be on the classpath.Alternatively, you can indeed run only a few tests with ant, setting the gwt.junit.testcase.includes property (it defaults to **/*Suite.class), something like (from the "user" subproject) ant -Dgwt.junit.testcase.includes=**/requestfactory/client/ui/EditorTest.class test.dev.htmlunit test web.htmlunit