diff --git a/core/usecases/src/main/java/org/reparationservice/usecases/customer/add/AddCustomerInteractor.java b/core/usecases/src/main/java/org/reparationservice/usecases/customer/add/AddCustomerInteractor.java
index 088c90e..ac21e95 100644
--- a/core/usecases/src/main/java/org/reparationservice/usecases/customer/add/AddCustomerInteractor.java
+++ b/core/usecases/src/main/java/org/reparationservice/usecases/customer/add/AddCustomerInteractor.java
@@ -5,17 +5,28 @@
 import org.reparationservice.requestor.UseCaseRequest;
 
 public final class AddCustomerInteractor implements UseCaseActivator {
-	private final CustomerGateway customers;
-  private final UseCaseRequest request;
+  private final CustomerGateway customers;
 
-	public AddCustomerInteractor(CustomerGateway customers, UseCaseRequest request) {
-		this.customers = customers;
-		this.request = request;
-	}
+  public AddCustomerInteractor(CustomerGateway customers) {
+    if (customers == null)
+      throw new CustomerGatewayCannotBeNull();
+    this.customers = customers;
+  }
 
-	@Override
-	public void execute(UseCaseRequest request) {
-		long customerId = ((AddCustomerRequest) this.request).getId();
-		customers.addCustomer(customerId);	
-	}
+  @Override
+  public void execute(UseCaseRequest request) {
+    if (request == null)
+      throw new RequestCannotBeNull();
+
+    long customerId = ((AddCustomerRequest) request).getId();
+    customers.addCustomer(customerId);
+  }
+
+  class RequestCannotBeNull extends RuntimeException {
+    private static final long serialVersionUID = -8424684392205119848L;
+  }
+
+  class CustomerGatewayCannotBeNull extends RuntimeException {
+    private static final long serialVersionUID = 6821771280959420623L;
+  }
 }
diff --git a/core/usecases/src/test/java/org/reparationservice/usecases/customer/add/AddCustomerInteractorTest.java b/core/usecases/src/test/java/org/reparationservice/usecases/customer/add/AddCustomerInteractorTest.java
index 419ce9a..d3bde3d 100644
--- a/core/usecases/src/test/java/org/reparationservice/usecases/customer/add/AddCustomerInteractorTest.java
+++ b/core/usecases/src/test/java/org/reparationservice/usecases/customer/add/AddCustomerInteractorTest.java
@@ -2,37 +2,57 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+import de.bechte.junit.runners.context.HierarchicalContextRunner;
 import org.junit.Before;
 import org.junit.Test;
 
+import org.junit.runner.RunWith;
 import org.reparationservice.doubles.CustomerGatewaySpy;
 import org.reparationservice.entities.customer.Customer;
 import org.reparationservice.requestor.UseCaseActivator;
 
+@RunWith(HierarchicalContextRunner.class)
 public class AddCustomerInteractorTest {
-	private static final long CUSTOMER_ID = 1;
-	private CustomerGatewaySpy customersSpy;
-
-	@Before
-	public void setUp() {
-		customersSpy = new CustomerGatewaySpy();
-	}
-
-	@Test
-	public void gatewayWasNotCalledWhenInteractorNotYetExecuted() {
-		assertThat(customersSpy.addCustomerWasCalled()).isFalse();
-	}
-
-	@Test
-	public void executeOperation() {
-	  AddCustomerRequest request = new AddCustomerRequest(CUSTOMER_ID);
-		UseCaseActivator addCustomer = new AddCustomerInteractor(customersSpy, request);
-			
-    addCustomer.execute(request);
-
-		assertThat(customersSpy.addCustomerWasCalled()).isTrue();
-		Customer addedCustomer = customersSpy.getCustomer();
-		assertThat(addedCustomer).isNotNull();
-		assertThat(addedCustomer.getId()).isEqualTo(CUSTOMER_ID);
-	}
+  private static final long CUSTOMER_ID = 1;
+  private CustomerGatewaySpy customersSpy;
+
+  @Before
+  public void setUp() {
+    customersSpy = new CustomerGatewaySpy();
+  }
+
+  @Test
+  public void gatewayWasNotCalledWhenInteractorNotYetExecuted() {
+    assertThat(customersSpy.addCustomerWasCalled()).isFalse();
+  }
+
+  @Test(expected = AddCustomerInteractor.CustomerGatewayCannotBeNull.class)
+  public void customerGatewayCannotBeNull() {
+    new AddCustomerInteractor(null);
+  }
+
+  public class InteractorCreated {
+    private UseCaseActivator addCustomer;
+
+    @Before
+    public void givenInteractor(){
+      addCustomer = new AddCustomerInteractor(customersSpy);
+    }
+
+    @Test(expected = AddCustomerInteractor.RequestCannotBeNull.class)
+    public void requestCannotBeNull() {
+      addCustomer.execute(null);
+    }
+
+    @Test
+    public void executeOperation() {
+      AddCustomerRequest request = new AddCustomerRequest(CUSTOMER_ID);
+      addCustomer.execute(request);
+
+      assertThat(customersSpy.addCustomerWasCalled()).isTrue();
+      Customer addedCustomer = customersSpy.getCustomer();
+      assertThat(addedCustomer).isNotNull();
+      assertThat(addedCustomer.getId()).isEqualTo(CUSTOMER_ID);
+    }
+  }
 }