diff --git a/pom.xml b/pom.xml
index 5232e37..ac5e85a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -34,6 +34,9 @@
     </scm>
 
     <properties>
+        <java.version>1.8</java.version>
+        <maven.compiler.source>${java.version}</maven.compiler.source>
+        <maven.compiler.target>${java.version}</maven.compiler.target>
         <tiles-maven-plugin.version>2.16</tiles-maven-plugin.version>
         <kemitix-maven-tiles.version>2.1.2</kemitix-maven-tiles.version>
         <kemitix-tiles.version>0.9.0</kemitix-tiles.version>
@@ -42,7 +45,7 @@
 
         <javax-mail.version>1.4.7</javax-mail.version>
         <subethasmtp.version>3.1.7</subethasmtp.version>
-        <junit.version>4.13</junit.version>
+        <junit.version>5.6.1</junit.version>
         <mockito-core.version>3.3.3</mockito-core.version>
         <simple-java-mail.version>3.1.1</simple-java-mail.version>
         <spring-framework.version>5.2.4.RELEASE</spring-framework.version>
@@ -52,6 +55,7 @@
         <jacoco-class-missed-count-maximum>1</jacoco-class-missed-count-maximum>
         <mon.version>2.1.0</mon.version>
         <spotbugs.version>4.0.1</spotbugs.version>
+        <assertj.version>3.15.0</assertj.version>
     </properties>
 
     <dependencies>
@@ -71,8 +75,8 @@
             <version>${subethasmtp.version}</version>
         </dependency>
         <dependency>
-            <groupId>junit</groupId>
-            <artifactId>junit</artifactId>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
             <version>${junit.version}</version>
             <scope>test</scope>
         </dependency>
@@ -82,6 +86,12 @@
             <version>${mockito-core.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj.version}</version>
+            <scope>test</scope>
+        </dependency>
         <dependency><!-- for Issue1Test -->
             <groupId>org.codemonkey.simplejavamail</groupId>
             <artifactId>simple-java-mail</artifactId>
diff --git a/src/test/java/net/kemitix/wiser/assertions/AbstractWiserTest.java b/src/test/java/net/kemitix/wiser/assertions/AbstractWiserTest.java
index 2eb8437..8f385b1 100644
--- a/src/test/java/net/kemitix/wiser/assertions/AbstractWiserTest.java
+++ b/src/test/java/net/kemitix/wiser/assertions/AbstractWiserTest.java
@@ -1,7 +1,7 @@
 package net.kemitix.wiser.assertions;
 
-import org.junit.After;
-import org.junit.Before;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
 import org.subethamail.wiser.Wiser;
 
 import java.io.IOException;
@@ -17,7 +17,7 @@ abstract class AbstractWiserTest {
 
     private Wiser wiser;
 
-    @Before
+    @BeforeEach
     public void setUp() throws IOException {
         port = findFreePort();
         wiser = new Wiser(port);
@@ -31,7 +31,7 @@ abstract class AbstractWiserTest {
         }
     }
 
-    @After
+    @AfterEach
     public void tearDown() {
         wiser.stop();
     }
diff --git a/src/test/java/net/kemitix/wiser/assertions/Issue1Test.java b/src/test/java/net/kemitix/wiser/assertions/Issue1Test.java
index d8d1fe7..46d6d31 100644
--- a/src/test/java/net/kemitix/wiser/assertions/Issue1Test.java
+++ b/src/test/java/net/kemitix/wiser/assertions/Issue1Test.java
@@ -2,7 +2,7 @@ package net.kemitix.wiser.assertions;
 
 import org.codemonkey.simplejavamail.Mailer;
 import org.codemonkey.simplejavamail.email.Email;
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 
 import javax.mail.Message;
 
diff --git a/src/test/java/net/kemitix/wiser/assertions/Issue6Test.java b/src/test/java/net/kemitix/wiser/assertions/Issue6Test.java
index 2ec4535..1753142 100644
--- a/src/test/java/net/kemitix/wiser/assertions/Issue6Test.java
+++ b/src/test/java/net/kemitix/wiser/assertions/Issue6Test.java
@@ -1,7 +1,6 @@
 package net.kemitix.wiser.assertions;
 
-import org.junit.Test;
-
+import org.junit.jupiter.api.Test;
 import org.springframework.mail.SimpleMailMessage;
 import org.springframework.mail.javamail.JavaMailSenderImpl;
 
diff --git a/src/test/java/net/kemitix/wiser/assertions/WiserAssertionsTest.java b/src/test/java/net/kemitix/wiser/assertions/WiserAssertionsTest.java
index 9eb2645..0b6f039 100644
--- a/src/test/java/net/kemitix/wiser/assertions/WiserAssertionsTest.java
+++ b/src/test/java/net/kemitix/wiser/assertions/WiserAssertionsTest.java
@@ -1,9 +1,10 @@
 package net.kemitix.wiser.assertions;
 
-import org.junit.Test;
+import org.junit.jupiter.api.Test;
 import org.subethamail.wiser.Wiser;
 
-import static org.junit.Assert.assertNotNull;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.AssertionsForClassTypes.assertThatExceptionOfType;
 
 import java.io.IOException;
 import java.util.logging.Level;
@@ -75,14 +76,17 @@ public class WiserAssertionsTest extends AbstractWiserTest {
      * Test {@link WiserAssertions#withContent(java.lang.String)} where the
      * content of the email does not match.
      */
-    @Test(expected = AssertionError.class)
+    @Test
     public void testContentNotMatches() {
         //given
         final String body = "message body";
         //when
         sendMimeMultipartMessage("from", "to", "subject", body);
         //then
-        assertReceivedMessage().withContent("Other body");
+        assertThatExceptionOfType(AssertionError.class)
+                .isThrownBy(() ->
+                        assertReceivedMessage()
+                                .withContent("Other body"));
     }
 
     /**
@@ -103,14 +107,17 @@ public class WiserAssertionsTest extends AbstractWiserTest {
      * Test {@link WiserAssertions#withContentContains(String)} where the
      * content of the email does not match.
      */
-    @Test(expected = AssertionError.class)
+    @Test
     public void testContentContainsNotMatches() {
         //given
         final String body = "message body";
         //when
         sendMimeMultipartMessage("from", "to", "subject", body);
         //then
-        assertReceivedMessage().withContentContains("agebo");
+        assertThatExceptionOfType(AssertionError.class)
+                .isThrownBy(() ->
+                        assertReceivedMessage()
+                                .withContentContains("agebo"));
     }
 
     /**
@@ -133,14 +140,17 @@ public class WiserAssertionsTest extends AbstractWiserTest {
      * Test {@link WiserAssertions#from(java.lang.String)} can detect when mail
      * is not sent from a user.
      */
-    @Test(expected = AssertionError.class)
+    @Test
     public void testFromNotMatches() {
         //given
         final String from = "bob@a.com";
         //when
         sendMimeMultipartMessage(from, "to", "subject", "body");
         //then
-        assertReceivedMessage().from("lisa@c.com");
+        assertThatExceptionOfType(AssertionError.class)
+                .isThrownBy(() ->
+                        assertReceivedMessage()
+                                .from("lisa@c.com"));
     }
 
     /**
@@ -149,7 +159,8 @@ public class WiserAssertionsTest extends AbstractWiserTest {
      */
     @Test
     public void testInstantiate() {
-        assertNotNull(assertReceivedMessage());
+        assertThat(assertReceivedMessage())
+                .isNotNull();
     }
 
     /**
@@ -171,14 +182,17 @@ public class WiserAssertionsTest extends AbstractWiserTest {
      * Test {@link WiserAssertions#withSubjectContains(java.lang.String)} where
      * the subject does not contain the expected fragment.
      */
-    @Test(expected = AssertionError.class)
+    @Test
     public void testSubjectContainsNotMatches() {
         //given
         final String fragment = "foo";
         //when
         sendMimeMultipartMessage("from", "to", "subject tail", "body");
         //then
-        assertReceivedMessage().withSubjectContains(fragment);
+        assertThatExceptionOfType(AssertionError.class)
+                .isThrownBy(() ->
+                        assertReceivedMessage()
+                                .withSubjectContains(fragment));
     }
 
     /**
@@ -199,14 +213,17 @@ public class WiserAssertionsTest extends AbstractWiserTest {
      * Test {@link WiserAssertions#withSubject(java.lang.String)} where the
      * message does not have the subject expected.
      */
-    @Test(expected = AssertionError.class)
+    @Test
     public void testSubjectNotMatches() {
         //given
         final String subject = "message subject";
         //when
         sendMimeMultipartMessage("from", "to", subject, "body");
         //then
-        assertReceivedMessage().withSubject("other subject");
+        assertThatExceptionOfType(AssertionError.class)
+                .isThrownBy(() ->
+                        assertReceivedMessage()
+                                .withSubject("other subject"));
     }
 
     /**
@@ -228,14 +245,17 @@ public class WiserAssertionsTest extends AbstractWiserTest {
      * is not sent from a user.
      *
      */
-    @Test(expected = AssertionError.class)
+    @Test
     public void testToNotMatches() {
         //given
         final String to = "carl@b.com";
         //when
         sendMimeMultipartMessage("from", to, "subject", "body");
         //then
-        assertReceivedMessage().to("bob@a.com");
+        assertThatExceptionOfType(AssertionError.class)
+                .isThrownBy(() ->
+                        assertReceivedMessage()
+                                .to("bob@a.com"));
     }
 
 }