Update test dependency in pom.xml

pom.xml

@@ -46,6 +46,7 @@
         <!-- Test libs -->
         <junit.version>4.12</junit.version>
         <mockito.version>2.21.0</mockito.version>
+        <assertj.version>3.12.1</assertj.version>
         <awaitility.version>3.1.5</awaitility.version>
         <powermock.version>2.0.0</powermock.version>
 
@@ -158,6 +159,12 @@
                 <version>${mockito.version}</version>
                 <scope>test</scope>
             </dependency>
+            <dependency>
+                <groupId>org.assertj</groupId>
+                <artifactId>assertj-core</artifactId>
+                <version>${assertj.version}</version>
+                <scope>test</scope>
+            </dependency>
             <dependency>
                 <groupId>org.awaitility</groupId>
                 <artifactId>awaitility</artifactId>