diff --git a/lesson_15/tdd/tdd_app/src/main/java/com/codedifferently/lesson15/Employee.java b/lesson_15/tdd/tdd_app/src/main/java/com/codedifferently/lesson15/Employee.java
index 49aaabbd7..54f978190 100644
--- a/lesson_15/tdd/tdd_app/src/main/java/com/codedifferently/lesson15/Employee.java
+++ b/lesson_15/tdd/tdd_app/src/main/java/com/codedifferently/lesson15/Employee.java
@@ -45,4 +45,15 @@ public double getSalary() {
   public void setSalary(double salary) {
     this.salary = salary;
   }
+
+  public String getDetails() {
+    return "Employee: "
+        + name
+        + ", Department: "
+        + department
+        + " , ID: "
+        + id
+        + " , Salary: "
+        + (int) salary;
+  }
 }
diff --git a/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeManagerTest.java b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeManagerTest.java
new file mode 100644
index 000000000..cd214b9a1
--- /dev/null
+++ b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeManagerTest.java
@@ -0,0 +1,89 @@
+package com.codedifferently.lesson15;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class EmployeeManagerTest {
+  private EmployeeManager employeeManager;
+
+  @BeforeEach
+  public void setUp() {
+    employeeManager = new EmployeeManager();
+  }
+
+  @Test
+  void testAddEmployee() {
+    // Arrange
+    Employee employee = new Employee(1, "John Doe", null, 0);
+
+    // Act
+    employeeManager.addEmployee(employee);
+
+    // Assert
+    assertEquals(1, employeeManager.getEmployeeCount());
+  }
+
+  @Test
+  void testUpdateEmployee() {
+    // Arrange
+    Employee employee = new Employee(1, "John Doe", null, 0);
+    Employee updatedEmployee = new Employee(1, "Jane Doe", null, 0);
+
+    // Act
+    employeeManager.addEmployee(employee);
+    employeeManager.updateEmployee(updatedEmployee);
+
+    // Assert
+    Employee retrievedEmployee = employeeManager.getEmployee(1);
+    assertEquals(updatedEmployee.getName(), retrievedEmployee.getName());
+  }
+
+  @Test
+  void testGetEmployee() {
+    // Arrange
+    Employee employee = new Employee(1, "John Doe", null, 0);
+
+    // Act
+    employeeManager.addEmployee(employee);
+    Employee retrievedEmployee = employeeManager.getEmployee(1);
+
+    // Assert
+    assertEquals(employee.getId(), retrievedEmployee.getId());
+    assertEquals(employee.getName(), retrievedEmployee.getName());
+  }
+
+  @Test
+  void testRemoveEmployee() {
+
+    Employee employee = new Employee(1, "John Doe", null, 0);
+
+    employeeManager.addEmployee(employee);
+    assertEquals(1, employeeManager.getEmployeeCount());
+
+    employeeManager.removeEmployee(1);
+    assertEquals(0, employeeManager.getEmployeeCount());
+  }
+
+  @Test
+  void testGetEmployeeCount() {
+
+    assertEquals(0, employeeManager.getEmployeeCount());
+
+    employeeManager.addEmployee(new Employee(1, "John Doe", null, 0));
+    employeeManager.addEmployee(new Employee(2, "Jane Doe", null, 0));
+
+    assertEquals(2, employeeManager.getEmployeeCount());
+  }
+
+  @Test
+  void testGetEmployeeThrowsExceptionForNonExistentId() {
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> {
+          employeeManager.getEmployee(999);
+        });
+  }
+}
diff --git a/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeTest.java b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeTest.java
new file mode 100644
index 000000000..569c5e9d0
--- /dev/null
+++ b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeTest.java
@@ -0,0 +1,120 @@
+package com.codedifferently.lesson15;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class EmployeeTest {
+  @Test
+  void testGetDepartment() {
+    // Arrange
+    Employee employee = new Employee(12345, "John Doe", "Engineering", 75000);
+
+    // Act
+    String actualDepartment = employee.getDepartment();
+
+    // Assert
+    String expectedDepartment = "Engineering";
+    assertEquals(expectedDepartment, actualDepartment);
+  }
+
+  @Test
+  void testGetDetails() {
+    // Arrange
+    Employee employee = new Employee(12345, "John Doe", "Engineering", 75000);
+
+    // Act
+    String actualDetails = employee.getDetails();
+
+    // Assert
+    String expectedDetails =
+        "Employee: John Doe, Department: Engineering , ID: 12345 , Salary: 75000";
+    assertEquals(expectedDetails, actualDetails);
+  }
+
+  @Test
+  void testGetId() {
+    // Arrange
+    Employee employee = new Employee(12345, "John Doe", "Engineering", 75000);
+
+    // Act
+    int actualEmployeeID = employee.getId();
+
+    // Assert
+    int expectedEmployeeID = 12345;
+    assertEquals(expectedEmployeeID, actualEmployeeID);
+  }
+
+  @Test
+  void testGetName() {
+    // Arrange
+    Employee employee = new Employee(12345, "John Doe", "Engineering", 75000);
+
+    // Act
+    employee.getName();
+
+    // Assert
+    assertEquals("John Doe", employee.getName());
+  }
+
+  @Test
+  void testGetSalary() {
+    // Arrange
+    Employee employee = new Employee(12345, "John Doe", "Engineering", 75000);
+
+    // Act
+    double expectedSalary = employee.getSalary();
+
+    // Assert
+    double actualSalary = 75000;
+    assertEquals(expectedSalary, actualSalary);
+  }
+
+  @Test
+  void testSetDepartment() {
+    // Arrange
+    Employee employee = new Employee(12345, "John Doe", "", 75000);
+
+    // Act
+    employee.setDepartment("Engineering");
+
+    // Assert
+    assertEquals("Engineering", employee.getDepartment());
+  }
+
+  @Test
+  void testSetId() {
+    // Arrange
+    Employee employee = new Employee(0, "John Doe", "", 75000);
+
+    // Act
+    employee.setId(12345);
+
+    // Assert
+    assertEquals(12345, employee.getId());
+  }
+
+  @Test
+  void testSetName() {
+    // Arrange
+    Employee employee = new Employee(12345, "", "Engineering", 75000);
+
+    // Act
+    employee.setName("Alice Johnson");
+
+    // Assert
+    assertEquals("Alice Johnson", employee.getName());
+  }
+
+  @Test
+  void testSetSalary() {
+    // Arrange
+    Employee employee = new Employee(12345, "", "Engineering", 0);
+
+    // Act
+    employee.setSalary(75000);
+
+    // Assert
+    assertEquals(75000, employee.getSalary());
+  }
+}