anchor.diff:    scheduleForProjects(Iterable<Project> projects()) async {
       theProjects = projects();
       processor = new TestProcessor();
  -    final JefeProjectGraph graph =
  -        await getRootProjects(theProjects.toSet());
  +    final JefeProjectGraph graph = await getRootProjects(theProjects.toSet());
       return graph.processDepthFirst(processor);
     }
   
  
positive.code:       final project1 = aProject('project1');
        final project2 = aProject('project2', dependencies: [project1]);
        final project3 = aProject('project3');
        final project4 = aProject('project3', dependencies: [project3, project2]);
  
        expectThat(
            withTheseProjects: () => [project1, project4, project3, project2],
  
negative.code:     group(
          'when no projects provided',
          () =>
              expectThat(withTheseProjects: () => [], weGetTheseInvocations: []),
          skip: false);
  
      group('for a single project that has no dependencies', () {
        final project1 = aProject('project1');
  