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QLC-2.1) Setup and first test

  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. In FindHighestNumber project create a new package that ends with .topicmanager

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

  5. Code Block
    languagec#
    namespace TopicManagerTests
{
  package xx.yy.zz.topicmanagerservice

public class TopicManagerTests
   
{
   
    @Test
    public    public void findvoid 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));
        }
    }
}

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

  7. Clean the code up so that the class is in a namespace package called TopicManagerService topicmanagerservice

  8. 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 top 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.

  9. Code Block
    languagec#
        public class TopicManagerTests
    {
        @Test
        public   void  find_heighest_score_in_empty_array_return_empty_array()
        {
            // Arrange
            ArrayList<TopicScores> array = new ArrayList<>();
            TopicManager cut = new TopicManager();
            ArrayList<TopicTopScore> expectedResult = new ArrayList<>();
      
            // Act
            ArrayList<TopicTopScore> result = cut.findTopicHighScores( array );
      
            // Assert
            assertEquals( expectedResult, result );
        
        }      
    }

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

  11. Code Block
    languagec#
    class TopicManager
{
   ArrayList<TopicTopScore> findTopicHighScores(ArrayList<TopicScores> array)
   {
      return new ArrayList<>();
   }
}

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

  13. So you will also need the following pieces of codewill also need the following pieces of code

  14. Code Block
    package com.s2s.demos.topicmanager;

class Topic
{
   private  String topicName;
   int      score;
   
   public   Topic( String topicName, int score)
   {
      this.topicName = topicName;
      this.score = score;
   }

   public String getTopicName()
   {
      return topicName;
   }

   public int getScore()
   {
      return score;
   }
}
  15. Code Block
    public class TopicTopScore
{
   
}
  16. Code Block
    public class TopicScores
{
   
}

...

  1. Implement this second test

  2. Code Block
    languagejava
       @Test
   public void find_heighest_score_with_array_of_one_return_array_of_one()
   {
       // Arrange
       int[] scores = { 56, 67, 45, 89 };
       String topicName = "Physics";
       ArrayList<TopicScores> topicScores = new ArrayList<>();
       topicScores.add(new TopicScores(topicName, scores));
   
       TopicManager cut = new TopicManager();
       ArrayList<TopicTopScore> expectedResult = new ArrayList<>();
       expectedResult.add(new TopicTopScore(topicName, 89));

       // Act
       ArrayList<TopicTopScore> result = cut.findTopicHighScores(topicScores);

       assertEquals(expectedResult.get(0).getTopicName(), result.get(0).getTopicName());
       assertEquals(expectedResult.get(0).getTopScore(), result.get(0).getTopScore() );
   }

  3. And here is the implementation class

  4. Code Block
    languagec#java
    class TopicManager
{
   private final HighestNumberFinder highestNumberFinder = new HighestNumberFinder();

   ArrayList<TopicTopScore> findTopicHighScores(ArrayList<TopicScores> array)
   {
      ArrayList<TopicTopScore> topScores = new ArrayList<>();

      if(array.size() == 1)
      {
          TopicScores ts = array.get(0);
          int topScore = highestNumberFinder.findHighestNumber(ts.getScores());

          topScores.add(new TopicTopScore(ts.getTopicName(), topScore));
      }
      return topScores;
   }
}

  5. Updated TopicScores.java

  6. Code Block
    languagejava
    package com.s2s.demos.topicmanager;

public class TopicScores
{
   private String topicName;
   private int[] scores;
   
   public TopicScores(String topicName, int[] scores)
   {
      this.topicName = topicName;
      this.scores = scores;
   }
   
   public String   getTopicName()
   {
      return topicName;
   }
   
   public   int[] getScores()
   {
      return scores;
   }
}

  7. Updated TopicTopScores.java

  8. Code Block
    languagejava
    public class TopicTopScore
{
   private  String topicName;
   private  int topScore;

   public TopicTopScore(String topicName, int score)
   {
      this.topScore = score;
      this.topicName = topicName;
   }
   
   public String getTopicName()
   {
      return topicName;
   }

   public int getTopScore()
   {
      return topScore;
   }
}

  9. Looking back at TopicManager, Line 3 represents the elephant in the code

    1. We already have tests for the HighestNumberFinder class, and yes class TopicManager requires HighestNumberFinder. But the coupling between these two classes is such that we cannot test TopicManger independently of HighestNumberFinder. Actually, this is a code smell.

    2. we can not substitute out HighestNumberFinder, this also is a code smell.

    3. We can remove the code smell by injecting HighestNumberFinder into TopicManager, when TopicManager is created.

  10. Modify TopicManager as follows

    1. remove the creation of HighestNumberFinder at line 5

    2. Pass an instance of a HighestNumberFinder into TopicManager as a constructor parameter

  11. Code Block
    languagec#java
    public class TopicManager
{
    private HighestNumberFinder highestNumberFinder;

    public  TopicManager( HighestNumberFinder hnf )
    {
        highestNumberFinder = hnf;
    }

    public TopicTopScore[] findTopicHighScores(TopicScores[] array)
    {
        if(array.Length == 1)
        {
            List<TopicTopScore> topScores = new List<TopicTopScore>();

            TopicScores ts = array[0];
            int topScore = highestNumberFinder.findHighestNumber(ts.Scores);

            topScores.Add(new TopicTopScore(ts.TopicName, topScore));

            return topScores.ToArray();
        }
        else
            return Array.Empty<TopicTopScore>();
    }
}

  12. Refactor the tests so that they run. You should not have to change any of the test data.

...

Begin by creating a new test

Code Block
languagejava
   @Test
   public void find_heighest_score_with_array_of_one_return_array_of_one_using_stub()
   {
       // Arrange
       int[] scores = { 56, 67, 45, 89 };
       String topicName = "Physics";
       ArrayList<TopicScores> topicScores = new ArrayList<>();
       topicScores.add(new TopicScores(topicName, scores));
   
       // Use a stub version of HighestNumberFinder
       com.s2s.demos.topicmanager.HighestNumberFinder hnf = 
                        new com.s2s.demos.topicmanager.HighestNumberFinder();
       TopicManager cut = new TopicManager(hnf);
       ArrayList<TopicTopScore> expectedResult = new ArrayList<>();
       expectedResult.add(new TopicTopScore(topicName, 89));

       // Act
       ArrayList<TopicTopScore> result = cut.findTopicHighScores(topicScores);

       
       assertEquals(expectedResult.get(0).getTopicName(), result.get(0).getTopicName());
       assertEquals(expectedResult.get(0).getTopScore(), result.get(0).getTopScore() );
   }

There will be a number of errors in the code, we will eliminate them one by one

Here is the Stub you will use (create it in the test folder - it’s not production code)

Code Block
languagec#java
package com.s2s.demos.topicmanager;

public class HighestNumberFinder
{
    public int findHighestNumber(int[] array)
    {
        return 89;
    }
}

The stub is substituted in line 1311.

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, is typed against com.s2s.demos.findhighestnumber.fin.HighestNumberFinder. So namespaces packages do not offer us the solution we are looking for.

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

  1. Create a new interface that is part of the production code, and create it in the com.s2s.demos.findhighestnumber package

  2. Code Block
    languagec#java
    package com.s2s.demos.findhighestnumber;

public interface IHighestNumberFinder
{
   int findHighestNumber(int[] values);
}

  3. Modify the production version and test version of HighestNumberFinder, so that they both implement the interface IHighestNumberFinder

  4. Here is the stub version

  5. Code Block
    languagejava
    package com.s2s.demos.topicmanager;

import com.s2s.demos.findhighestnumber.IHighestNumberFinder;

// The STUB version
public class HighestNumberFinder implements IHighestNumberFinder
{
   @Override
    public int findHighestNumber(int[] array)
    {
        return 89;
    }
}

  6. Here is the production version

  7. Code Block
    languagejava
    package com.s2s.demos.findhighestnumber.fin;

import com.s2s.demos.findhighestnumber.IHighestNumberFinder;

public  class HighestNumberFinder implements IHighestNumberFinder
{
   @Override
    public int findHighestNumber(int[] array)
    {
        int highestSoFar = Integer.MIN_VALUE;
        
        for( int val : array )
        {
            if( val > highestSoFar )
                highestSoFar = val;
        }
        return highestSoFar;
    }    
}

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

  9. Code Block
    languagejava
    package com.s2s.demos.topicmanager;

import com.s2s.demos.findhighestnumber.IHighestNumberFinder;
import java.util.ArrayList;

class TopicManager
{
   private final IHighestNumberFinder highestNumberFinder;

   public  TopicManager()
   {
      this.highestNumberFinder = null;
   }
   
   public  TopicManager( IHighestNumberFinder hnf )
   {
       highestNumberFinder = hnf;
   }
   ...

  10. You should find that the test is no longer in an error state

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

...

•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

...