anchor.diff:      TestLogger logger = new TestLogger();
       AnalysisEngine.instance.logger = logger;
       try {
  -      Source librarySource = addSource(r'''
  +      Source source = addSource(r'''
     const int a = c;
     const int b = a;
     const int c = b;''');
  -      LibraryElement libraryElement = resolve2(librarySource);
  +      LibraryElement libraryElement = resolve2(source);
         CompilationUnit unit =
  -          analysisContext.resolveCompilationUnit(librarySource, libraryElement);
  -      analysisContext.computeErrors(librarySource);
  +          analysisContext.resolveCompilationUnit(source, libraryElement);
  +      analysisContext.computeErrors(source);
         expect(unit, isNotNull);
         ConstantValueComputer computer = _makeConstantValueComputer();
  -      computer.add(unit, librarySource, librarySource);
  +      computer.add(unit, source, source);
         computer.computeValues();
         NodeList<CompilationUnitMember> members = unit.declarations;
         expect(members, hasLength(3));
  
positive.code:   }
  
    @override
    void beforeGetConstantInitializers(ConstructorElement constructor) {
      // Make sure we properly recorded the dependency.
      expect(
          computer.referenceGraph.containsPath(_nodeBeingEvaluated, constructor),
          isTrue);
    }
  
    @override
    void beforeGetEvaluationResult(ConstantEvaluationTarget constant) {
      // Make sure we properly recorded the dependency.
      expect(computer.referenceGraph.containsPath(_nodeBeingEvaluated, constant),
          isTrue);
    }
  
    @override
    void beforeGetFieldEvaluationResult(FieldElementImpl field) {
      // Make sure we properly recorded the dependency.
      expect(computer.referenceGraph.containsPath(_nodeBeingEvaluated, field),
          isTrue);
    }
  
    @override
    void beforeGetParameterDefault(ParameterElement parameter) {
      // Make sure we properly recorded the dependency.
      expect(computer.referenceGraph.containsPath(_nodeBeingEvaluated, parameter),
          isTrue);
    }
  }
  
  
negative.code: 
    ConstantValueComputer _makeConstantValueComputer() {
      ConstantEvaluationValidator_ForTest validator =
          new ConstantEvaluationValidator_ForTest(analysisContext2);
      validator.computer = new ConstantValueComputer(
          analysisContext2,
          analysisContext2.typeProvider,
  