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..c5a9b7c21 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 +45,13 @@ public double getSalary() {
   public void setSalary(double salary) {
     this.salary = salary;
   }
+
+  public boolean containsKey(Object id2) {
+    // TODO Auto-generated method stub
+    throw new UnsupportedOperationException("Unimplemented method 'containsKey'");
+  }
+
+  public Employee getDetails(Employee employee) {
+    return employee;
+  }
 }
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..556bc1240
--- /dev/null
+++ b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeManagerTest.java
@@ -0,0 +1,80 @@
+package com.codedifferently.lesson15;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class EmployeeManagerTest {
+
+  private EmployeeManager employeeManager;
+  private Employee employee;
+
+  @BeforeEach
+  void setUp() {
+    employeeManager = new EmployeeManager();
+    employee = new Employee(1, "Edgar Allen Poe", "Publications", 0.0);
+    employeeManager.addEmployee(employee);
+  }
+
+  @Test
+  void testAddEmployee() {
+    // Arrange
+    Employee newEmployee = new Employee(2, "Sheet Ghost", "Administration", 0.0);
+    // Act
+    employeeManager.addEmployee(newEmployee);
+    // Assert
+    assertThat(employeeManager.getEmployee(2)).isEqualTo(newEmployee);
+  }
+
+  @Test
+  void testGetEmployee() {
+    // Act
+    Employee actualEmployee = employeeManager.getEmployee(1);
+    // Assert
+    assertThat(actualEmployee).isEqualTo(employee);
+  }
+
+  @Test
+  void testUpdateEmployee() {
+    // Arrange
+    Employee updatedEmployee = new Employee(1, "Frankenstein", "Development", 0.0);
+    // Act
+    employeeManager.updateEmployee(updatedEmployee);
+    Employee actualEmployee = employeeManager.getEmployee(1);
+    // Assert
+    assertThat(actualEmployee).isEqualTo(updatedEmployee);
+  }
+
+  @Test
+  void testRemoveEmployee() {
+    // Act
+    employeeManager.removeEmployee(1);
+    Employee removedEmployee = employeeManager.getEmployee(1);
+    // Assert
+    assertEquals(0, employeeManager.getEmployeeCount(), "Employee count should be 0");
+    assertNull(removedEmployee, "Employee should be removed from directory.");
+  }
+
+  @Test
+  void testAssertEmployeeInCollection() {
+    // Arrange & Act & Assert
+    assertThatThrownBy(() -> employeeManager.getEmployee(52))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessage("Employee does not exist in collection with Id 1");
+  }
+
+  @Test
+  void testGetEmployeeCount() {
+    // Arrange
+    Employee addNew1 = new Employee(2, "Dracula", "Medical", 0.0);
+    Employee addNew2 = new Employee(3, "Blade", "Security", 0.0);
+    // Act
+    employeeManager.addEmployee(addNew1);
+    employeeManager.addEmployee(addNew2);
+    // Assert
+    assertEquals(3, employeeManager.getEmployeeCount());
+  }
+}
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..ce4d39185
--- /dev/null
+++ b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/EmployeeTest.java
@@ -0,0 +1,19 @@
+package com.codedifferently.lesson15;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+public class EmployeeTest {
+  private Employee employee;
+
+  @Test
+  void testGetDetails() {
+    // Arrange
+    employee = new Employee(1, "Jet Li", "Specialist", 110.00);
+    // Act
+    Employee actualDetails = employee.getDetails(employee);
+    // Assert
+    assertThat(actualDetails).isEqualTo(employee);
+  }
+}
diff --git a/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/Lesson15Test.java b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/Lesson15Test.java
index cd6ef511e..8b1378917 100644
--- a/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/Lesson15Test.java
+++ b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/lesson15/Lesson15Test.java
@@ -1,19 +1 @@
-package com.codedifferently.lesson15;
 
-import static org.assertj.core.api.Assertions.assertThat;
-
-import org.junit.jupiter.api.Test;
-
-class Lesson15Test {
-
-  @Test
-  public void testLesson15() {
-    assertThat(new Lesson15()).isNotNull();
-  }
-
-  @Test
-  public void testGetGreeting() {
-    // Act
-    Lesson15.main(null);
-  }
-}