@Test
public void getSourceFile() {

  assertThat(groovyFileSystem.sourceFiles()).isEmpty();
  fileSystem.add(new DefaultInputFile("", "fake.file"));
  assertThat(groovyFileSystem.sourceFiles()).isEmpty();
  fileSystem.add(new DefaultInputFile("", "fake.groovy").setLanguage(Groovy.KEY));
  assertThat(groovyFileSystem.sourceFiles()).hasSize(1);
}