Add unit test for processCreationForm in OwnerController with validation errors

src/test/java/org/springframework/samples/petclinic/owner/OwnerControllerTest.java

@@ -0,0 +1,56 @@
+package org.springframework.samples.petclinic.owner;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.test.web.servlet.MockMvc;
+import org.springframework.test.web.servlet.setup.MockMvcBuilders;
+import org.springframework.validation.BindingResult;
+import org.springframework.web.servlet.mvc.support.RedirectAttributes;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
+
+@ExtendWith(MockitoExtension.class)
+class OwnerControllerTest {
+
+	@Mock
+	private OwnerRepository ownerRepository;
+
+	@Mock
+	private BindingResult result;
+
+	@Mock
+	private RedirectAttributes redirectAttributes;
+
+	@InjectMocks
+	private OwnerController ownerController;
+
+	private MockMvc mockMvc;
+
+	@BeforeEach
+	void setup() {
+		mockMvc = MockMvcBuilders.standaloneSetup(ownerController).build();
+	}
+
+	@Test
+	@DisplayName("Test processCreationForm with validation errors")
+	void testProcessCreationFormWithValidationErrors() {
+		Owner owner = new Owner();
+
+		doReturn(true).when(result).hasErrors();
+
+		String view = ownerController.processCreationForm(owner, result, redirectAttributes);
+
+		assertThat(view).isEqualTo("owners/createOrUpdateOwnerForm");
+		verify(result).hasErrors();
+		verifyNoInteractions(ownerRepository);
+	}
+
+}