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

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

3. Code Block
   language c#
   namespace TopicManagerTests { package xx.yy.zz.topicmanagerservice 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)); } } }

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

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

6. 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.

7. Code Block
   language c#
   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 ); } }

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

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

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

11. So you will also need the following pieces of code

12. 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; } }

13. Code Block
    public class TopicTopScore { }

14. Code Block
    public class TopicScores { }

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1. Implement this second test

2. Code Block
   language java
   @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
   language c#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
   language java
   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
   language java
   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
    language c#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.

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