スタブ API を使用したモックフレームワークの作成

1@isTest
2public class MockProvider implements System.StubProvider {
3    
4    public Object handleMethodCall(Object stubbedObject, String stubbedMethodName, 
5        Type returnType, List<Type> listOfParamTypes, List<String> listOfParamNames, 
6        List<Object> listOfArgs) {
7        
8        // The following debug statements show an example of logging 
9        // the invocation of a mocked method.
10       
11        // You can use the method name and return type to determine which method was called.
12        System.debug('Name of stubbed method: ' + stubbedMethodName);
13        System.debug('Return type of stubbed method: ' + returnType.getName());
14        
15        // You can also use the parameter names and types to determine which method 
16        // was called.
17        for (integer i =0; i < listOfParamNames.size(); i++) {
18            System.debug('parameter name: ' + listOfParamNames.get(i));
19            System.debug('  parameter type: ' + listOfParamTypes.get(i).getName());
20        }
21        
22        // This shows the actual parameter values passed into the stubbed method at runtime.
23        System.debug('number of parameters passed into the mocked call: ' + 
24            listOfArgs.size());
25        System.debug('parameter(s) sent into the mocked call: ' + listOfArgs);
26        
27        // This is a very simple mock provider that returns a hard-coded value 
28        // based on the return type of the invoked.
29        if (returnType.getName() == 'String')
30            return '8/8/2016';
31        else 
32            return null;
33    }
34}

1public class MockUtil {
2    private MockUtil(){}
3
4    public static MockProvider getInstance() {
5        return new MockProvider();
6    }
7    
8     public static Object createMock(Type typeToMock) {
9        // Invoke the stub API and pass it our mock provider to create a 
10        // mock class of typeToMock.
11        return Test.createStub(typeToMock, MockUtil.getInstance());
12    }
13}

1@isTest 
2public class DateFormatterTest {   
3    @isTest 
4    public static void testGetFormattedDate() {
5        // Create a mock version of the DateHelper class.
6        DateHelper mockDH = (DateHelper)MockUtil.createMock(DateHelper.class);
7        DateFormatter df = new DateFormatter();
8        
9        // Use the mocked object in the test.
10        System.assertEquals('Today\'s date is 8/8/2016', df.getFormattedDate(mockDH));
11    }
12}