Bump test dependencies

Author: acogoluegnes

build.gradle

@@ -43,10 +43,10 @@ ext {
 	springAmqpVersion = '2.2.10.RELEASE'
 
 	// Testing
-	mockitoVersion = '3.5.15'
+	mockitoVersion = '3.6.0'
 	junitPlatformVersion = '1.7.0'
 	junitJupiterVersion  = '5.7.0'
-	assertjVersion = '3.17.2'
+	assertjVersion = '3.18.0'
 
 	javadocLinks = ["https://docs.oracle.com/javase/8/docs/api/",
 					"https://www.reactive-streams.org/reactive-streams-1.0.3-javadoc/",