Minor code changes are the following:

-Removed unused variables from few files.
-Added null assertions in some tests.
-Removed unnecessary throw exceptions.

src/main/java/org/springframework/samples/petclinic/vet/Vet.java

@@ -57,10 +57,6 @@ public class Vet extends Person {
 		return this.specialties;
 	}
 
-	protected void setSpecialtiesInternal(Set<Specialty> specialties) {
-		this.specialties = specialties;
-	}
-
 	@XmlElement
 	public List<Specialty> getSpecialties() {
 		List<Specialty> sortedSpecs = new ArrayList<>(getSpecialtiesInternal());

src/test/java/org/springframework/samples/petclinic/MySqlIntegrationTests.java

@@ -58,7 +58,7 @@ class MySqlIntegrationTests {
 	private RestTemplateBuilder builder;
 
 	@Test
-	void testFindAll() throws Exception {
+	void testFindAll() {
 		vets.findAll();
 		vets.findAll(); // served from cache
 	}

src/test/java/org/springframework/samples/petclinic/PetClinicIntegrationTests.java

@@ -44,7 +44,7 @@ public class PetClinicIntegrationTests {
 	private RestTemplateBuilder builder;
 
 	@Test
-	void testFindAll() throws Exception {
+	void testFindAll() {
 		vets.findAll();
 		vets.findAll(); // served from cache
 	}

src/test/java/org/springframework/samples/petclinic/PostgresIntegrationTests.java

@@ -17,6 +17,7 @@
 package org.springframework.samples.petclinic;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assumptions.assumeTrue;
 
 import java.util.Arrays;
@@ -114,7 +115,16 @@ public class PostgresIntegrationTests {
 				Arrays.sort(names);
 				for (String name : names) {
 					String resolved = environment.getProperty(name);
-					String value = source.getProperty(name).toString();
+
+					assertNotNull(resolved, "resolved environment property: " + name + " is null.");
+
+					Object sourceProperty = source.getProperty(name);
+
+					assertNotNull(sourceProperty, "source property was expecting an object but is null.");
+
+					assertNotNull(sourceProperty.toString(), "source property toString() returned null.");
+
+					String value = sourceProperty.toString();
 					if (resolved.equals(value)) {
 						log.info(name + "=" + resolved);
 					}

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

@@ -68,7 +68,7 @@ class PetTypeFormatterTests {
 	}
 
 	@Test
-	void shouldThrowParseException() throws ParseException {
+	void shouldThrowParseException() {
 		given(this.pets.findPetTypes()).willReturn(makePetTypes());
 		Assertions.assertThrows(ParseException.class, () -> {
 			petTypeFormatter.parse("Fish", Locale.ENGLISH);

src/test/java/org/springframework/samples/petclinic/service/ClinicServiceTests.java

@@ -205,8 +205,6 @@ class ClinicServiceTests {
 		owner6.addVisit(pet7.getId(), visit);
 		this.owners.save(owner6);
 
-		owner6 = this.owners.findById(6);
-
 		assertThat(pet7.getVisits()) //
 			.hasSize(found + 1) //
 			.allMatch(value -> value.getId() != null);

src/test/java/org/springframework/samples/petclinic/system/CrashControllerTests.java

@@ -30,7 +30,7 @@ import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 // luck ((plain(st) UNIT test)! :)
 class CrashControllerTests {
 
-	CrashController testee = new CrashController();
+	final CrashController testee = new CrashController();
 
 	@Test
 	void testTriggerException() {

src/test/java/org/springframework/samples/petclinic/vet/VetTests.java

@@ -18,6 +18,7 @@ package org.springframework.samples.petclinic.vet;
 import org.junit.jupiter.api.Test;
 import org.springframework.util.SerializationUtils;
 
+import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**