Use Apache Commons Math for calculations and implement service tests

Implement TestResultService tests and supporting entity builders.
Switch to Apache Commons Math library for descriptive statistics.

7 files changed, 360 insertions, 42 deletions

diff --git a/pom.xml b/pom.xml
index 0281f72..55b3297 100644
--- a/pom.xml
+++ b/pom.xml
@@ -65,6 +65,12 @@
         </dependency>
 
         <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-math3</artifactId>
+            <version>3.6.1</version>
+        </dependency>
+
+        <dependency>
             <groupId>com.h2database</groupId>
             <artifactId>h2</artifactId>
             <scope>runtime</scope>
diff --git a/src/main/java/com/stileeducation/markr/entity/TestResult.java b/src/main/java/com/stileeducation/markr/entity/TestResult.java
index cb7cea5..0d68f62 100644
--- a/src/main/java/com/stileeducation/markr/entity/TestResult.java
+++ b/src/main/java/com/stileeducation/markr/entity/TestResult.java
@@ -8,6 +8,16 @@ import java.util.Objects;
 @Table(name = "test_results")
 public class TestResult {
 
+  public TestResult() {
+  }
+
+  public TestResult(Long id, Student student, Test test, Integer marksAwarded) {
+    this.id = id;
+    this.student = student;
+    this.test = test;
+    this.marksAwarded = marksAwarded;
+  }
+
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Long id;
diff --git a/src/main/java/com/stileeducation/markr/service/TestResultsService.java b/src/main/java/com/stileeducation/markr/service/TestResultsService.java
index 8d1b314..95b42f3 100644
--- a/src/main/java/com/stileeducation/markr/service/TestResultsService.java
+++ b/src/main/java/com/stileeducation/markr/service/TestResultsService.java
@@ -7,16 +7,18 @@ import com.stileeducation.markr.entity.TestResult;
 import com.stileeducation.markr.repository.StudentRepository;
 import com.stileeducation.markr.repository.TestRepository;
 import com.stileeducation.markr.repository.TestResultRepository;
+import org.apache.commons.math3.stat.descriptive.moment.StandardDeviation;
+import org.apache.commons.math3.stat.descriptive.rank.Percentile;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.stereotype.Service;
 
 import java.util.List;
 import java.util.Optional;
-import java.util.stream.Collectors;
 
 @Service
 public class TestResultsService {
 
+  public static final boolean IS_BIAS_CORRECTED = false;
   @Autowired
   private TestResultRepository testResultRepository;
 
@@ -78,68 +80,64 @@ public class TestResultsService {
         .orElse(0.0);
   }
 
-  public double calculateStandardDeviationOfTestResults(List<TestResult> results, double mean) {
+  public double calculateStandardDeviationOfTestResults(List<TestResult> results) {
     if (results.isEmpty()) {
-      return 0.0; // or throw an exception if no results are found
+      return 0.0;
     }
+    double[] marks =
+        results.stream()
+            .mapToDouble(TestResult::getMarksAwarded)
+            .toArray();
 
-    // Calculate the variance
-    double variance = results.stream()
-        .mapToDouble(result -> Math.pow(result.getMarksAwarded() - mean, 2))
-        .average()
-        .orElse(0.0);
-
-    // Return the standard deviation
-    return Math.sqrt(variance);
+    StandardDeviation standardDeviation = new StandardDeviation(IS_BIAS_CORRECTED);
+    return standardDeviation.evaluate(marks);
   }
 
-  public double calculatePercentile(List<Integer> sortedMarks, double percentile) {
-    if (sortedMarks.isEmpty()) {
+  public double calculate25thPercentile(List<TestResult> results) {
+    if (results.isEmpty()) {
       return 0.0;
     }
-    int index = (int) Math.floor(percentile / 100.0 * sortedMarks.size()) - 1;
-    return sortedMarks.get(Math.min(index, sortedMarks.size() - 1));
+    double[] marks =
+        results.stream()
+            .mapToDouble(TestResult::getMarksAwarded)
+            .toArray();
+    return new Percentile().evaluate(marks, 25.0);
   }
 
-  public List<Integer> getSortedMarks(List<TestResult> testResults) {
-    return testResults.stream()
-        .map(TestResult::getMarksAwarded)
-        .sorted()
-        .collect(Collectors.toList());
-  }
-
-  public double calculate25thPercentile(List<Integer> sortedMarks) {
-    return calculatePercentile(sortedMarks, 25.0);
-  }
-
-  public double calculate50thPercentile(List<Integer> sortedMarks) {
-    return calculatePercentile(sortedMarks, 50.0);
+  public double calculate50thPercentile(List<TestResult> results) {
+    if (results.isEmpty()) {
+      return 0.0;
+    }
+    double[] marks =
+        results.stream()
+            .mapToDouble(TestResult::getMarksAwarded)
+            .toArray();
+    return new Percentile().evaluate(marks, 50.0);
   }
 
-  public double calculate75thPercentile(List<Integer> sortedMarks) {
-    return calculatePercentile(sortedMarks, 75.0);
+  public double calculate75thPercentile(List<TestResult> results) {
+    if (results.isEmpty()) {
+      return 0.0;
+    }
+    double[] marks =
+        results.stream()
+            .mapToDouble(TestResult::getMarksAwarded)
+            .toArray();
+    return new Percentile().evaluate(marks, 75.0);
   }
 
   public AggregatedTestResultsDTO aggregateTestResults(String testId) {
     List<TestResult> testResults = findAllByTestId(testId);
-    List<Integer> sortedMarks = getSortedMarks(testResults);
 
     AggregatedTestResultsDTO results = new AggregatedTestResultsDTO();
 
     results.setMean(calculateMeanOfTestResults(testResults));
-
-    results.setStddev(calculateStandardDeviationOfTestResults(testResults, results.getMean()));
-
+    results.setStddev(calculateStandardDeviationOfTestResults(testResults));
     results.setMin(calculateMinOfTestResults(testResults));
-
     results.setMax(calculateMaxOfTestResults(testResults));
-
-    results.setP25(calculate25thPercentile(sortedMarks));
-
-    results.setP50(calculate50thPercentile(sortedMarks));
-
-    results.setP75(calculate75thPercentile(sortedMarks));
-
+    results.setP25(calculate25thPercentile(testResults));
+    results.setP50(calculate50thPercentile(testResults));
+    results.setP75(calculate75thPercentile(testResults));
     results.setCount(testResults.size());
 
     return results;
diff --git a/src/test/java/com/stileeducation/markr/service/TestResultsServiceTest.java b/src/test/java/com/stileeducation/markr/service/TestResultsServiceTest.java
new file mode 100644
index 0000000..474d731
--- /dev/null
+++ b/src/test/java/com/stileeducation/markr/service/TestResultsServiceTest.java
@@ -0,0 +1,175 @@
+package com.stileeducation.markr.service;
+
+import com.stileeducation.markr.entity.Student;
+import com.stileeducation.markr.entity.TestResult;
+import com.stileeducation.markr.repository.StudentRepository;
+import com.stileeducation.markr.repository.TestRepository;
+import com.stileeducation.markr.repository.TestResultRepository;
+import com.stileeducation.markr.util.StudentBuilder;
+import com.stileeducation.markr.util.TestBuilder;
+import com.stileeducation.markr.util.TestResultBuilder;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+
+class TestResultsServiceTest {
+
+  private static Student student1;
+  private static Student student2;
+  private static Student student3;
+  private static Student student4;
+
+  private static com.stileeducation.markr.entity.Test test1;
+
+  private static TestResult testResult1;
+  private static TestResult testResult2;
+  private static TestResult testResult3;
+  private static TestResult testResult4;
+  private static TestResult testResult5;
+  private static TestResult testResult6;
+
+  private static List<TestResult> test1Results;
+
+  @Mock
+  private TestResultRepository testResultRepository;
+
+  @Mock
+  private StudentRepository studentRepository;
+
+  @Mock
+  private TestRepository testRepository;
+
+  @InjectMocks
+  private TestResultsService testResultsService;
+
+  @BeforeAll
+  static void setupTestData() {
+    student1 = new StudentBuilder()
+        .withId(1L)
+        .withStudentNumber("555123")
+        .withFirstName("Emily")
+        .withLastName("Clark")
+        .build();
+
+    student2 = new StudentBuilder()
+        .withId(2L)
+        .withStudentNumber("555456")
+        .withFirstName("James")
+        .withLastName("Taylor")
+        .build();
+
+    student3 = new StudentBuilder()
+        .withId(3L)
+        .withStudentNumber("555789")
+        .withFirstName("Sophia")
+        .withLastName("Martinez")
+        .build();
+
+    student4 = new StudentBuilder()
+        .withId(4L)
+        .withStudentNumber("555012")
+        .withFirstName("Liam")
+        .withLastName("Anderson")
+        .build();
+
+    test1 = new TestBuilder()
+        .withId(1L)
+        .withTestId("1234")
+        .withMarksAvailable(100)
+        .build();
+
+    testResult1 = new TestResultBuilder()
+        .withStudent(student1)
+        .withTest(test1)
+        .withMarksAwarded(10)
+        .build();
+
+    testResult2 = new TestResultBuilder()
+        .withStudent(student2)
+        .withTest(test1)
+        .withMarksAwarded(20)
+        .build();
+
+    testResult3 = new TestResultBuilder()
+        .withStudent(student3)
+        .withTest(test1)
+        .withMarksAwarded(40)
+        .build();
+
+    testResult4 = new TestResultBuilder()
+        .withStudent(student4)
+        .withTest(test1)
+        .withMarksAwarded(50)
+        .build();
+
+    testResult5 = new TestResultBuilder()
+        .withStudent(student3)
+        .withTest(test1)
+        .withMarksAwarded(70)
+        .build();
+
+    testResult6 = new TestResultBuilder()
+        .withStudent(student4)
+        .withTest(test1)
+        .withMarksAwarded(80)
+        .build();
+
+    test1Results = List.of(testResult1, testResult2, testResult3, testResult4, testResult5, testResult6);
+  }
+
+  @BeforeEach
+  void setUp() {
+    MockitoAnnotations.openMocks(this);
+  }
+
+  @Test
+  void calculateMeanOfTestResults() {
+    double mean = testResultsService.calculateMeanOfTestResults(test1Results);
+    assertEquals(45.0, mean, 0.01);
+  }
+
+  @Test
+  void calculateMinOfTestResults() {
+    double min = testResultsService.calculateMinOfTestResults(test1Results);
+    assertEquals(10.0, min, 0.01);
+  }
+
+  @Test
+  void calculateMaxOfTestResults() {
+    double max = testResultsService.calculateMaxOfTestResults(test1Results);
+    assertEquals(80.0, max, 0.01);
+  }
+
+  @Test
+  void calculateStandardDeviationOfTestResults() {
+    double standardDeviationOfTestResults = testResultsService.calculateStandardDeviationOfTestResults(test1Results);
+    assertEquals(25, standardDeviationOfTestResults, 0.01);
+  }
+
+  @Test
+  void calculate25thPercentile() {
+    double percentile = testResultsService.calculate25thPercentile(test1Results);
+    assertEquals(17.5, percentile, 0.01);
+  }
+
+  @Test
+  void calculate50thPercentile() {
+    double percentile = testResultsService.calculate50thPercentile(test1Results);
+    assertEquals(45, percentile, 0.01);
+  }
+
+  @Test
+  void calculate75thPercentile() {
+    double percentile = testResultsService.calculate75thPercentile(test1Results);
+    assertEquals(72.5, percentile, 0.01);
+  }
+
+}
\ No newline at end of file
diff --git a/src/test/java/com/stileeducation/markr/util/StudentBuilder.java b/src/test/java/com/stileeducation/markr/util/StudentBuilder.java
new file mode 100644
index 0000000..5189f19
--- /dev/null
+++ b/src/test/java/com/stileeducation/markr/util/StudentBuilder.java
@@ -0,0 +1,50 @@
+package com.stileeducation.markr.util;
+
+import com.stileeducation.markr.entity.Student;
+import com.stileeducation.markr.entity.TestResult;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class StudentBuilder {
+  private Long id;
+  private String firstName;
+  private String lastName;
+  private String studentNumber;
+  private Set<TestResult> testResults = new HashSet<>();
+
+  public StudentBuilder withId(Long id) {
+    this.id = id;
+    return this;
+  }
+
+  public StudentBuilder withFirstName(String firstName) {
+    this.firstName = firstName;
+    return this;
+  }
+
+  public StudentBuilder withLastName(String lastName) {
+    this.lastName = lastName;
+    return this;
+  }
+
+  public StudentBuilder withStudentNumber(String studentNumber) {
+    this.studentNumber = studentNumber;
+    return this;
+  }
+
+  public StudentBuilder withTestResults(Set<TestResult> testResults) {
+    this.testResults = testResults;
+    return this;
+  }
+
+  public Student build() {
+    Student student = new Student();
+    student.setId(id);
+    student.setFirstName(firstName);
+    student.setLastName(lastName);
+    student.setStudentNumber(studentNumber);
+    student.setTestResults(testResults);
+    return student;
+  }
+}
\ No newline at end of file
diff --git a/src/test/java/com/stileeducation/markr/util/TestBuilder.java b/src/test/java/com/stileeducation/markr/util/TestBuilder.java
new file mode 100644
index 0000000..5c513f3
--- /dev/null
+++ b/src/test/java/com/stileeducation/markr/util/TestBuilder.java
@@ -0,0 +1,43 @@
+package com.stileeducation.markr.util;
+
+import com.stileeducation.markr.entity.Test;
+import com.stileeducation.markr.entity.TestResult;
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class TestBuilder {
+  private Long id;
+  private String testId;
+  private Integer marksAvailable;
+  private Set<TestResult> testResults = new HashSet<>();
+
+  public TestBuilder withId(Long id) {
+    this.id = id;
+    return this;
+  }
+
+  public TestBuilder withTestId(String testId) {
+    this.testId = testId;
+    return this;
+  }
+
+  public TestBuilder withMarksAvailable(Integer marksAvailable) {
+    this.marksAvailable = marksAvailable;
+    return this;
+  }
+
+  public TestBuilder withTestResults(Set<TestResult> testResults) {
+    this.testResults = testResults;
+    return this;
+  }
+
+  public Test build() {
+    Test test = new Test();
+    test.setId(id);
+    test.setTestId(testId);
+    test.setMarksAvailable(marksAvailable);
+    test.setTestResults(testResults);
+    return test;
+  }
+}
diff --git a/src/test/java/com/stileeducation/markr/util/TestResultBuilder.java b/src/test/java/com/stileeducation/markr/util/TestResultBuilder.java
new file mode 100644
index 0000000..db26e15
--- /dev/null
+++ b/src/test/java/com/stileeducation/markr/util/TestResultBuilder.java
@@ -0,0 +1,36 @@
+package com.stileeducation.markr.util;
+
+import com.stileeducation.markr.entity.Student;
+import com.stileeducation.markr.entity.Test;
+import com.stileeducation.markr.entity.TestResult;
+
+public class TestResultBuilder {
+  private Long id;
+  private Student student;
+  private Test test;
+  private Integer marksAwarded;
+
+  public TestResultBuilder withId(Long id) {
+    this.id = id;
+    return this;
+  }
+
+  public TestResultBuilder withStudent(Student student) {
+    this.student = student;
+    return this;
+  }
+
+  public TestResultBuilder withTest(Test test) {
+    this.test = test;
+    return this;
+  }
+
+  public TestResultBuilder withMarksAwarded(Integer marksAwarded) {
+    this.marksAwarded = marksAwarded;
+    return this;
+  }
+
+  public TestResult build() {
+    return new TestResult(id, student, test, marksAwarded);
+  }
+}
\ No newline at end of file