FileRef implementation = createFile("testImplementation",
"<gxp:implements interface='testInterface' />",
"<gxp:param name='foo' type='String' />");
compileFiles(refInterface, implementation);
assertAlert(new SchemaMismatchError(
pos(2,1), "com.google.gxp.compiler.errortests.testImplementation"));
assertNoUnexpectedAlerts();
}