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The HighestNumberFinder is designed to return an integer representing the number in a group of numbers. This can easily be stubbed out.Here is the Stub

Begin by creating a new test

namespace TopicManagerService
{[Test]
      public class HighestNumberFinderpublic void find_heighest_score_with_array_of_one_return_array_of_one_using_stub()
  {      {
  public int findHighestNumber(int[] values)       // Arrange
{             return 89;int[] scores = { 56, 67, 45, 89 };
            string topicName = "Physics";
            }TopicScores[] topicScores = { new TopicScores(topicName, scores) }
}

But when you try and use this class in the tests, you should see type errors. This is because, in the implementation unit of TopicManager, it's typed against HighestNumberFinder in a namespace called FindHighestNumberService.v6. So namespaces do not offer us the solution we are looking for.

Here are the modified tests

using NUnit.Framework;

namespace TopicManagerService
{;
            publicIHighestNumberFinder hnf class= TopicManagerTests
new TopicManagerServiceStubs.HighestNumberFinder();
   {         [Test]TopicManager cut = new TopicManager(hnf);
    public void find_heighest_score_in_empty_array_return_empty_array()      TopicTopScore[] expectedResult = { new TopicTopScore(topicName, 89) };

       // Arrange    // Act
       TopicScores[] topicScores = Array.Empty<TopicScores>();     TopicTopScore[]        HighestNumberFinder hnf = new HighestNumberFinder(result = cut.findTopicHighScores(topicScores);

           TopicManager cut = new TopicManager(hnf);// Assert
             TopicTopScore[] expectedResult = Array.Empty<TopicTopScore>(Assert.AreEqual(result[0].TopicName, expectedResult[0].TopicName);
             // ActAssert.AreEqual(result[0].TopScore, expectedResult[0].TopScore);
        }
    TopicTopScore[] result = cut.findTopicHighScores(topicScores);}

Here is the Stub. We have put it in a different namespace in the test project

namespace TopicManagerServiceStubs
{
    public class HighestNumberFinder
    {
  // Assert     public        Assert.That(result, Is.EqualTo(expectedResult));int findHighestNumber(int[] values)
        }

      {
 [Test]         public void find_heighest_score_with_array_of_one_return_array_of_one()
 89;
       { }
           // Arrange
            int[] scores = { 56, 67, 45, 89 };
 }
}

But when you try and use this class in the tests, you should see type errors in all the tests. This is because, in the implementation unit of TopicManager, it's typed against HighestNumberFinder in a namespace called FindHighestNumberService.v6. So namespaces do not offer us the solution we are looking for.

Here are the updated tests. Alternatively, you could modify TopicManager so it has a default constructor, but you will need to think about different issues and more tests for if TopicManager default constructor is used.

using NUnit.Framework;

namespace TopicManagerService
{
    public class TopicManagerTests
    {
        [Test]
        public void find_heighest_score_in_empty_array_return_empty_array()
        {
          string topicName = "Physics";// Arrange
            TopicScores[] topicScores = { new TopicScores(topicName, scores) }Array.Empty<TopicScores>();
            HighestNumberFinder hnf = new HighestNumberFinder();
            TopicManager cut = new TopicManager(hnf);
            TopicTopScore[] expectedResult = {new TopicTopScore(topicName, 89)}Array.Empty<TopicTopScore>();

            // Act
            TopicTopScore[] result = cut.findTopicHighScores(topicScores);

            // Assert
            Assert.That(result, Is.EqualTo(expectedResult));
        }

        [Test]
// Assert       public void find_heighest_score_with_array_of_one_return_array_of_one()
   Assert.AreEqual(result[0].TopicName, expectedResult[0].TopicName);    {
        Assert.AreEqual(result[0].TopScore, expectedResult[0].TopScore);   // Arrange
    }      } }

Observe errors on lines 14 and 32.

We need to use interfaces. And the interface needs to be in a place that is available to both production code and tests.

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Create a new interface that is part of the HighestNumberFinder project

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 int[] scores = { 56, 67, 45, 89 };
    

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        string 

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topicName = "Physics";
   

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Copy HighestNumberFinder.v6 to HighestNumberFinderFinal and refactor the class so that it implements the interface above

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 TopicScores[] topicScores = { 

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new TopicScores(topicName, scores) };
     

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       HighestNumberFinder hnf 

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= 

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new HighestNumberFinder();
        

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    TopicManager cut = new TopicManager(hnf);

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TopicTopScore[] 

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expectedResult 

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= {new 

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TopicTopScore(topicName, 89)};

        

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 // Act
      

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      TopicTopScore[] result = cut.findTopicHighScores(topicScores);

  

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          // Assert
          

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Assert.AreEqual(result[0].TopicName, expectedResult[0].TopicName);
            

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Assert.AreEqual(result[0].TopScore, expectedResult[0].TopScore);
        }
    

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}
}

To give us more flexibility, we need to use an interface. And the interface needs to be in a place that is available to both production code and tests.

1. Create a new interface that is part of the HighestNumberFinder production project

2. Code Block
   language c#
   namespace FindHighestNumberService { public interface IHighestNumberFinder { if (values[i] > result)int findHighestNumber(int[] values); result = values[i]; } }

3. Copy HighestNumberFinder.v6 to HighestNumberFinderFinal

4. Refactor the class so that it implements the interface above

5. Code Block
   language c#
   using System; using FindHighestNumberService; namespace FindHighestNumberServiceFinal { public class EmptyArrayException : }Exception { return result;public EmptyArrayException(string message):base(message) } { } }

6. Refactor the tests so that the HighestNumberFinder is instantiated as follows

7. Code Block
   } IHighestNumberFinder hnf = new FindHighestNumberServiceFinal.HighestNumberFinder();

8. Refactor TopicManager so it now works with the interface IHighestNumberFinder and not directly with the implementation class

9. Rerun all your tests they should still be passing.

Now let’s substitute a stub in place of the real implementation of HighestNumberFinder.

1. Create a new called find_heighest_score_with_array_of_one_return_array_of_one_using_stub(), it's a copy of find_heighest_score_with_array_of_one_return_array_of_one()

2. Code Block
   language c#
   } public class HighestNumberFinder : IHighestNumberFinder { public int findHighestNumber(int[] values) { if (values.Length < 1) [Test] publicthrow void find_heighest_score_with_array_of_one_return_array_of_one_using_stub()new EmptyArrayException("Array is empty"); { int result = Int32.MinValue; //for Arrange(int i = 0; i < values.Length; i++) int[] scores = { 56, 67, 45, 89{ }; string topicName = "Physics"; if (values[i] > result) TopicScores[] topicScores = { new TopicScores(topicName, scores) }; result = values[i]; IHighestNumberFinder hnf = new FindHighestNumberServiceFinal.HighestNumberFinder(); } TopicManager cut = new TopicManager(hnf)return result; } TopicTopScore[] expectedResult = { new TopicTopScore(topicName, 89) }; } }

3. Modify the Stub version so it also implements IHighestNumberFinder

4. Refactor TopicManager so it now works with the interface IHighestNumberFinder and not directly with the implementation class

5. Code Block
   language c#
   namespace TopicManagerServiceStubs { public class TopicManager { // Act private TopicTopScore[] result = cut.findTopicHighScores(topicScores)IHighestNumberFinder highestNumberFinder; // Assert Assert.AreEqual(result[0].TopicName, expectedResult[0].TopicName);public TopicManager( IHighestNumberFinder hnf ) { Assert.AreEqual(result[0].TopScore, expectedResult[0].TopScore); highestNumberFinder = hnf; } }

6. Modify line 8 to

7. Code Block
   language c#
   } IHighestNumberFinder hnf = new TopicManagerService.HighestNumberFinder();

8. The error is because of TopicManagerTests.HighestNumberFinder does not implement the IHighestNumberFinder interface. Modify it so that it does.

9. Rerun the tests, they should all pass

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10. Rerun all your tests they should still be passing.

QLC-2.3 Limitations of Stubs, complete this TopicManager requirement

Add more tests to handle the last two requirements

•If the input is [{“Physics”, {56, 67, 45, 89}}, {“Art”, {87, 66, 78}], the result should be [{“Physics”, 89}, {“Art”, 87}]

One Only one of the results will failtests passes. Why?

Sample Solution

QLC-2.4 Mocks, complete the last TopicManager requirement

•If the input is [{“Physics”, {56, 67, 45, 89}}, {“Art”, {87, 66, 78}}, {“Comp Sci”, {45, 88, 97, 56}}], the result should be [{“Physics”, 89}, {“Art”, 87}, {“Comp Sci”, 97}]

Sample Solution