Add unit test for validate method in PetValidator class

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

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+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.junit.jupiter.MockitoExtension;
+import org.springframework.validation.BeanPropertyBindingResult;
+import org.springframework.validation.Errors;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@ExtendWith(MockitoExtension.class)
+@DisplayName("PetValidator Tests")
+class PetValidatorTest {
+
+	@InjectMocks
+	private PetValidator petValidator;
+
+	private Pet pet;
+
+	private Errors errors;
+
+	@BeforeEach
+	void setUp() {
+		pet = new Pet();
+		errors = new BeanPropertyBindingResult(pet, "pet");
+	}
+
+	@Test
+	@DisplayName("Validate Pet with missing fields")
+	void testValidatePetWithMissingFields() {
+		petValidator.validate(pet, errors);
+
+		assertThat(errors.getFieldError("name").getCode()).isEqualTo("required");
+		assertThat(errors.getFieldError("type").getCode()).isEqualTo("required");
+		assertThat(errors.getFieldError("birthDate").getCode()).isEqualTo("required");
+	}
+
+}