diff --git a/src/test/java/org/springframework/samples/petclinic/model/ValidatorTests.java b/src/test/java/org/springframework/samples/petclinic/model/ValidatorTests.java
index 151c0ce7016..e37a9656255 100644
--- a/src/test/java/org/springframework/samples/petclinic/model/ValidatorTests.java
+++ b/src/test/java/org/springframework/samples/petclinic/model/ValidatorTests.java
@@ -53,7 +53,7 @@ public void shouldNotValidateWhenFirstNameEmpty() {
         Set<ConstraintViolation<Person>> constraintViolations = validator
                 .validate(person);
 
-        assertThat(constraintViolations.size()).isEqualTo(1);
+        assertThat(constraintViolations).hasSize(1);
         ConstraintViolation<Person> violation = constraintViolations.iterator().next();
         assertThat(violation.getPropertyPath().toString()).isEqualTo("firstName");
         assertThat(violation.getMessage()).isEqualTo("must not be empty");
diff --git a/src/test/java/org/springframework/samples/petclinic/owner/PetTypeFormatterTests.java b/src/test/java/org/springframework/samples/petclinic/owner/PetTypeFormatterTests.java
index 47812a812ed..9ba43148019 100644
--- a/src/test/java/org/springframework/samples/petclinic/owner/PetTypeFormatterTests.java
+++ b/src/test/java/org/springframework/samples/petclinic/owner/PetTypeFormatterTests.java
@@ -26,10 +26,10 @@
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.Mock;
-import org.mockito.Mockito;
 import org.mockito.junit.MockitoJUnitRunner;
 
-import static org.junit.Assert.assertEquals;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
 
 /**
  * Test class for {@link PetTypeFormatter}
@@ -54,19 +54,19 @@ public void testPrint() {
         PetType petType = new PetType();
         petType.setName("Hamster");
         String petTypeName = this.petTypeFormatter.print(petType, Locale.ENGLISH);
-        assertEquals("Hamster", petTypeName);
+        assertThat(petTypeName).isEqualTo("Hamster");
     }
 
     @Test
     public void shouldParse() throws ParseException {
-        Mockito.when(this.pets.findPetTypes()).thenReturn(makePetTypes());
+        given(this.pets.findPetTypes()).willReturn(makePetTypes());
         PetType petType = petTypeFormatter.parse("Bird", Locale.ENGLISH);
-        assertEquals("Bird", petType.getName());
+        assertThat(petType.getName()).isEqualTo("Bird");
     }
 
     @Test(expected = ParseException.class)
     public void shouldThrowParseException() throws ParseException {
-        Mockito.when(this.pets.findPetTypes()).thenReturn(makePetTypes());
+        given(this.pets.findPetTypes()).willReturn(makePetTypes());
         petTypeFormatter.parse("Fish", Locale.ENGLISH);
     }
 
diff --git a/src/test/java/org/springframework/samples/petclinic/service/ClinicServiceTests.java b/src/test/java/org/springframework/samples/petclinic/service/ClinicServiceTests.java
index 8a7a2f0a5f7..c103caac0c4 100644
--- a/src/test/java/org/springframework/samples/petclinic/service/ClinicServiceTests.java
+++ b/src/test/java/org/springframework/samples/petclinic/service/ClinicServiceTests.java
@@ -79,17 +79,17 @@ public class ClinicServiceTests {
     @Test
     public void shouldFindOwnersByLastName() {
         Collection<Owner> owners = this.owners.findByLastName("Davis");
-        assertThat(owners.size()).isEqualTo(2);
+        assertThat(owners).hasSize(2);
 
         owners = this.owners.findByLastName("Daviss");
-        assertThat(owners.isEmpty()).isTrue();
+        assertThat(owners).isEmpty();
     }
 
     @Test
     public void shouldFindSingleOwnerWithPet() {
         Owner owner = this.owners.findById(1);
         assertThat(owner.getLastName()).startsWith("Franklin");
-        assertThat(owner.getPets().size()).isEqualTo(1);
+        assertThat(owner.getPets()).hasSize(1);
         assertThat(owner.getPets().get(0).getType()).isNotNull();
         assertThat(owner.getPets().get(0).getType().getName()).isEqualTo("cat");
     }
@@ -213,7 +213,7 @@ public void shouldAddNewVisitForPet() {
     @Test
     public void shouldFindVisitsByPetId() throws Exception {
         Collection<Visit> visits = this.visits.findByPetId(7);
-        assertThat(visits.size()).isEqualTo(2);
+        assertThat(visits).hasSize(2);
         Visit[] visitArr = visits.toArray(new Visit[visits.size()]);
         assertThat(visitArr[0].getDate()).isNotNull();
         assertThat(visitArr[0].getPetId()).isEqualTo(7);