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1. Create a new Test Project in the FindHighestNumber Solution

2. Install the packages you want (MSTest already installed, or NUnit - we are going to be using NUnit)

3. Create a new setup the new test class as shown here (remember you will have errors)

4. Code Block
   language c#
   namespace TopicManagerTests { public class TopicManagerTests { [Test] public void find_heighest_score_in_empty_array_return_empty_array() { // Arrange int[] array = {}; TopicManager cut = new TopicManager(); int[] expectedResult = {}; // Act Topic[] result = cut.findTopicHighScores(array); // Assert Assert.That(result, Is.EqualTo(result)); } } }

5. Create a new class called TopicManager in the FindHighestNumberService project

6. Clean the code up so that the class is in a namespace called TopicManagerService

7. Lines 9, 11, and 14 give us enough information to allow us to start thinking about what we are trying to design here. based on the requirements, we want to pass into the method findTopicHighScores an array of Topics and their accompanying scores. It should return the topic score of each Topic, we will call this TopicTopScore. Each item in the array being passed into the findTopicHighScores will be called TopicScores (plural I know, but it matches the context, you may want to lose the ‘s' at the end of the class name). Let’s refactor the code to reflect what we have outlined here.

8. Code Block
   language c#
   public class TopicManagerTests { [Test] public void find_heighest_score_in_empty_array_return_empty_array() { // Arrange TopicScores[] array = Array.Empty<TopicScores>(); TopicManager cut = new TopicManager(); TopicTopScore[] expectedResult = Array.Empty<TopicTopScore>(); // Act TopicTopScore[] result = cut.findTopicHighScores(array); // Assert Assert.That(result, Is.EqualTo(result)); } }

9. We are now in a good position to get VS to generate the findTopicHighScores with the correct signature

10. Code Block
    language c#
    namespace TopicManagerService { public class TopicManager // TopicManager.cs { public TopicTopScore[] findTopicHighScores(TopicScores[] array) { // This block oc code assumes that the input is an empty array, there is no need for an if statement return Array.Empty<TopicTopScore>(); } } }

11. Now we need to complete the first piece of implementation code to pass the test

12. So you should have will also need the following pieces of code

13. Code Block
    namespace TopicManagerService { public class TopicTopScore // TopicTopSscore.cs { } }

14. Code Block
    namespace TopicManagerService { public class TopicScores // TopicScores.cs { } }

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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
            int[] scores = { 56, 67, 45, 89 };
          return 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
{
    public class TopicManagerTests;
            IHighestNumberFinder hnf = new TopicManagerServiceStubs.HighestNumberFinder();
            TopicManager cut = new TopicManager(hnf);
       {     TopicTopScore[] expectedResult = { [Test]
  new TopicTopScore(topicName, 89) };

    public void find_heighest_score_in_empty_array_return_empty_array()         {
            // ArrangeAct
            TopicScoresTopicTopScore[] topicScoresresult = Arraycut.Empty<TopicScores>findTopicHighScores(topicScores);

           HighestNumberFinder hnf// =Assert
new HighestNumberFinder();             TopicManager cut = new TopicManager(hnfAssert.AreEqual(result[0].TopicName, expectedResult[0].TopicName);
            TopicTopScoreAssert.AreEqual(result[0].TopScore, expectedResult = Array.Empty<TopicTopScore>([0].TopScore);
        }
    // Act
            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 int findHighestNumber(int[] values)
       Assert.That(result, Is.EqualTo(expectedResult)); {
        }    return 89;
    [Test]    }
    public void find_heighest_score_with_array_of_one_return_array_of_one()
        {
            // Arrange
  }
}

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 int[] scores = { 56, 67, 45, 89 };
 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.AreEqualThat(result[0].TopicName, expectedResult[0].TopicNameIs.EqualTo(expectedResult));
        }

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

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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public void find_heighest_score_with_array_of_one_return_array_of_one()
     

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 {
   

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// Arrange
     

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

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int[] 

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scores = { 56, 67, 

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45, 

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89 

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};

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      string topicName = 

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"Physics";
          

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  TopicScores[] topicScores = { new TopicScores(topicName, scores) };
     

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 HighestNumberFinder 

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hnf 

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= new HighestNumberFinder();
   

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TopicManager 

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cut = new TopicManager(hnf);
        

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    TopicTopScore[] expectedResult = {new 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 { int result = values[i]findHighestNumber(int[] values); } } }

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 returnclass result;EmptyArrayException : Exception { } } }

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

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 TopicTopScore[] result{ = cut.findTopicHighScores(topicScores); private IHighestNumberFinder highestNumberFinder; // Assert public TopicManager( IHighestNumberFinder Assert.AreEqual(result[0].TopicName, expectedResult[0].TopicName);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();

   The error is because of TopicManagerTests

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   HighestNumberFinder does not implement the IHighestNumberFinder interface. Modify it so that it does.Rerun the tests, they should all pass

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

QLC-2.3 Limitations of Stubs, complete

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this TopicManager

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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}]

Only one of the tests 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