diff --git a/src/test/java/com/maxio/advancedbilling/controllers/CustomersControllerUpdateTest.java b/src/test/java/com/maxio/advancedbilling/controllers/CustomersControllerUpdateTest.java
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+++ b/src/test/java/com/maxio/advancedbilling/controllers/CustomersControllerUpdateTest.java
@@ -0,0 +1,226 @@
+package com.maxio.advancedbilling.controllers;
+
+import com.maxio.advancedbilling.TestClient;
+import com.maxio.advancedbilling.exceptions.ApiException;
+import com.maxio.advancedbilling.exceptions.CustomerErrorResponseException;
+import com.maxio.advancedbilling.models.CreateCustomer;
+import com.maxio.advancedbilling.models.CreateCustomerRequest;
+import com.maxio.advancedbilling.models.Customer;
+import com.maxio.advancedbilling.models.CustomerError;
+import com.maxio.advancedbilling.models.CustomerResponse;
+import com.maxio.advancedbilling.models.UpdateCustomer;
+import com.maxio.advancedbilling.models.UpdateCustomerRequest;
+import com.maxio.advancedbilling.models.containers.CustomerErrorResponseErrors;
+import org.apache.commons.lang3.RandomStringUtils;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+class CustomersControllerUpdateTest {
+
+    private final CustomersController customersController = TestClient.createClient().getCustomersController();
+
+    private Integer customerId;
+
+    @BeforeEach
+    void setUp() throws IOException, ApiException {
+        customerId = customersController
+                .createCustomer(new CreateCustomerRequest()
+                        .toBuilder()
+                        .customer(new CreateCustomer()
+                                .toBuilder()
+                                .firstName("Cathryn")
+                                .lastName("Washington")
+                                .email("martha@example.com")
+                                .reference(RandomStringUtils.randomAlphanumeric(10))
+                                .build()
+                        )
+                        .build()
+                )
+                .getCustomer()
+                .getId();
+    }
+
+    @Test
+    void shouldUpdateCustomerWithNewFirstName() throws IOException, ApiException {
+        // when
+        Customer customer = customersController
+                .updateCustomer(
+                        customerId,
+                        new UpdateCustomerRequest(new UpdateCustomer().toBuilder().firstName("Martha").build())
+                )
+                .getCustomer();
+
+        // then
+        assertThat(customer.getFirstName()).isEqualTo("Martha");
+        assertThat(customer.getLastName()).isEqualTo("Washington");
+        assertThat(customer.getEmail()).isEqualTo("martha@example.com");
+    }
+
+    @Test
+    void shouldUpdateCustomerWithNewLastName() throws IOException, ApiException {
+        // when
+        Customer customer = customersController
+                .updateCustomer(
+                        customerId,
+                        new UpdateCustomerRequest(new UpdateCustomer().toBuilder().lastName("Newman").build())
+                )
+                .getCustomer();
+
+        // then
+        assertThat(customer.getFirstName()).isEqualTo("Cathryn");
+        assertThat(customer.getLastName()).isEqualTo("Newman");
+        assertThat(customer.getEmail()).isEqualTo("martha@example.com");
+    }
+
+    @Test
+    void shouldUpdateCustomerWithNewEmail() throws IOException, ApiException {
+        // when
+        Customer customer = customersController
+                .updateCustomer(
+                        customerId,
+                        new UpdateCustomerRequest(new UpdateCustomer().toBuilder().email("company@test.com").build())
+                )
+                .getCustomer();
+
+        // then
+        assertThat(customer.getFirstName()).isEqualTo("Cathryn");
+        assertThat(customer.getLastName()).isEqualTo("Washington");
+        assertThat(customer.getEmail()).isEqualTo("company@test.com");
+    }
+
+    @Test
+    void shouldUpdateCustomerWithNewProperties() throws IOException, ApiException {
+        // when
+        Customer customer = customersController
+                .updateCustomer(
+                        customerId,
+                        new UpdateCustomerRequest(new UpdateCustomer()
+                                .toBuilder()
+                                .firstName("Martha")
+                                .lastName("Newman")
+                                .email("company@test.com")
+                                .country("US")
+                                .state("NY")
+                                .city("New York")
+                                .build()
+                        )
+                )
+                .getCustomer();
+
+        // then
+        assertThat(customer.getFirstName()).isEqualTo("Martha");
+        assertThat(customer.getLastName()).isEqualTo("Newman");
+        assertThat(customer.getEmail()).isEqualTo("company@test.com");
+        assertThat(customer.getCountry()).isEqualTo("US");
+        assertThat(customer.getState()).isEqualTo("NY");
+        assertThat(customer.getCity()).isEqualTo("New York");
+    }
+
+    @Test
+    void shouldReturnNullWhenNotExists() throws IOException, ApiException {
+        int notExistingCustomerId = 123;
+
+        // when
+        CustomerResponse customerResponse = customersController
+                .updateCustomer(notExistingCustomerId, new UpdateCustomerRequest());
+
+        // then
+        assertThat(customerResponse).isNull();
+    }
+
+    @Test
+    void shouldNotUpdateCustomerWhenRequestIsNull() {
+        // when - then
+        assertThatExceptionOfType(CustomerErrorResponseException.class)
+                .isThrownBy(() -> customersController.updateCustomer(customerId, null))
+                .withMessage("Unprocessable Entity (WebDAV)")
+                .satisfies(e -> {
+                    assertThat(e.getResponseCode()).isEqualTo(422);
+                    assertThat(e.getErrors().toString()).isEqualTo(
+                            CustomerErrorResponseErrors
+                                    .fromCustomerError(new CustomerError("can't be blank"))
+                                    .toString()
+                    );
+                });
+    }
+
+    @Test
+    void shouldNotUpdateCustomerWhenRequestIsEmpty() {
+        // when - then
+        assertThatExceptionOfType(CustomerErrorResponseException.class)
+                .isThrownBy(() -> customersController.updateCustomer(
+                        customerId,
+                        new UpdateCustomerRequest(new UpdateCustomer())
+                ))
+                .withMessage("Unprocessable Entity (WebDAV)")
+                .satisfies(e -> {
+                    assertThat(e.getResponseCode()).isEqualTo(422);
+                    assertThat(e.getErrors().toString()).isEqualTo(
+                            CustomerErrorResponseErrors
+                                    .fromCustomerError(new CustomerError("can't be blank"))
+                                    .toString()
+                    );
+                });
+    }
+
+    @ParameterizedTest
+    @MethodSource("argsForShouldNotUpdateCustomerWhenBasicParametersAreBlank")
+    void shouldNotUpdateCustomerWhenBasicParametersAreBlank(UpdateCustomer updateCustomer, List<String> errorMessages) {
+        // when - then
+        assertThatExceptionOfType(CustomerErrorResponseException.class)
+                .isThrownBy(() -> customersController.updateCustomer(
+                        customerId, new UpdateCustomerRequest(updateCustomer))
+                )
+                .withMessage("Unprocessable Entity (WebDAV)")
+                .satisfies(e -> {
+                    assertThat(e.getResponseCode()).isEqualTo(422);
+                    assertThat(e.getErrors().toString())
+                            .isEqualTo(CustomerErrorResponseErrors.fromListOfString(errorMessages).toString());
+                });
+    }
+
+    private static Stream<Arguments> argsForShouldNotUpdateCustomerWhenBasicParametersAreBlank() {
+        return Stream.of(
+                Arguments.of(
+                        new UpdateCustomer().toBuilder().firstName("").lastName("").email("").build(),
+                        Arrays.asList("First name: cannot be blank.", "Last name: cannot be blank.", "Email address: cannot be blank.")
+                ),
+                Arguments.of(
+                        new UpdateCustomer().toBuilder().firstName("").build(),
+                        Collections.singletonList("First name: cannot be blank.")
+                ),
+                Arguments.of(
+                        new UpdateCustomer().toBuilder().lastName("").build(),
+                        Collections.singletonList("Last name: cannot be blank.")
+                ),
+                Arguments.of(
+                        new UpdateCustomer().toBuilder().email("").build(),
+                        Collections.singletonList("Email address: cannot be blank.")
+                ),
+                Arguments.of(
+                        new UpdateCustomer().toBuilder().firstName("").lastName("").build(),
+                        Arrays.asList("First name: cannot be blank.", "Last name: cannot be blank.")
+                ),
+                Arguments.of(
+                        new UpdateCustomer().toBuilder().firstName("").email("").build(),
+                        Arrays.asList("First name: cannot be blank.", "Email address: cannot be blank.")
+                ),
+                Arguments.of(
+                        new UpdateCustomer().toBuilder().lastName("").email("").build(),
+                        Arrays.asList("Last name: cannot be blank.", "Email address: cannot be blank.")
+                )
+        );
+    }
+}