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..f79a34e2f 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 ID "
+        + this.id
+        + ", Name "
+        + this.getName()
+        + ", Department "
+        + this.getDepartment()
+        + ", Salary "
+        + this.getSalary();
+  }
 }
diff --git a/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/Employee/EmployeeTest.java b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/Employee/EmployeeTest.java
new file mode 100644
index 000000000..3319057b7
--- /dev/null
+++ b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/Employee/EmployeeTest.java
@@ -0,0 +1,61 @@
+package com.codedifferently.Employee;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import com.codedifferently.lesson15.Employee;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class EmployeeTest {
+  Employee employee;
+
+  @BeforeEach
+  void setUp() {
+    employee = new Employee(1545, "Ray Allen", "Lavatory", 50000.0);
+  }
+
+  @Test
+  void testId() {
+    // Act
+    employee.setId(1545);
+    int id = employee.getId();
+    // Assert
+    assertEquals(1545, id);
+  }
+
+  @Test
+  // Act
+  void testName() {
+    employee.setName("Ray Allen");
+    String name = employee.getName();
+    // Assert
+    assertEquals("Ray Allen", name);
+  }
+
+  @Test
+  // Act
+  void testDepartment() {
+    employee.setDepartment("Lavatory");
+    String department = employee.getDepartment();
+    // Assert
+    assertEquals("Lavatory", department);
+  }
+
+  @Test
+  // Act
+  void testSalary() {
+    employee.setSalary(50000.0);
+    Double salary = employee.getSalary();
+    // Assert
+    assertEquals(50000.0, salary);
+  }
+
+  @Test
+  void getDetails() {
+
+    String expected = "Employee ID 1545, Name Ray Allen, Department Lavatory, Salary 50000.0";
+    String actual = employee.getDetails();
+
+    assertEquals(expected, actual);
+  }
+}
diff --git a/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/EmployeeManager/EmployeeManagerTest.java b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/EmployeeManager/EmployeeManagerTest.java
new file mode 100644
index 000000000..43ca12749
--- /dev/null
+++ b/lesson_15/tdd/tdd_app/src/test/java/com/codedifferently/EmployeeManager/EmployeeManagerTest.java
@@ -0,0 +1,51 @@
+package com.codedifferently.EmployeeManager;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import com.codedifferently.lesson15.Employee;
+import com.codedifferently.lesson15.EmployeeManager;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class EmployeeManagerTest {
+  EmployeeManager employeeManager;
+  Employee employee;
+
+  @BeforeEach
+  void setUp() {
+    employeeManager = new EmployeeManager();
+    employee = new Employee(1545, "Ray Allen", "Lavatory", 50000.0);
+  }
+
+  @Test
+  void addEmployee() {
+    employeeManager.addEmployee(employee);
+    assertThat(employeeManager.getEmployee(1545)).isEqualTo(employee);
+  }
+
+  @Test
+  void removeEmployee() {
+    employeeManager.addEmployee(employee);
+    employeeManager.removeEmployee(employee.getId());
+    assertThat(employeeManager.getEmployeeCount()).isEqualTo(0);
+  }
+
+  @Test
+  void updateEmployee() {
+    employeeManager.addEmployee(employee);
+    Employee updatedEmployee = new Employee(1545, "Ray Allen", "Baller", 1000000.0);
+
+    employeeManager.updateEmployee(updatedEmployee);
+
+    assertThat(employeeManager.getEmployee(employee.getId()).getDepartment()).isEqualTo("Baller");
+    assertThat(employeeManager.getEmployee(employee.getId()).getSalary()).isEqualTo(1000000.0);
+  }
+
+  @Test
+  void unknownEmployee() {
+    assertThatThrownBy(() -> employeeManager.getEmployee(9999))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessageContaining("Employee does not in collection with id 9999");
+  }
+}