update library version and config useJUnitPlatform

Author: javajigi

build.gradle

@@ -9,6 +9,10 @@ repositories {
 }
 
 dependencies {
-    testCompile('org.junit.jupiter:junit-jupiter:5.4.2')
-    testCompile('org.assertj:assertj-core:3.11.1')
-}
+    testCompile('org.junit.jupiter:junit-jupiter:5.6.0')
+    testCompile('org.assertj:assertj-core:3.15.0')
+}
+
+test {
+    useJUnitPlatform()
+}