Upgrade Gradle IntelliJ plugin and make sure tests are run properly

Author: filiphr

build.gradle

@@ -2,7 +2,7 @@ import com.hierynomus.gradle.license.tasks.LicenseCheck
 import com.hierynomus.gradle.license.tasks.LicenseFormat
 
 plugins {
-    id "org.jetbrains.intellij" version "1.1.4"
+    id "org.jetbrains.intellij" version "1.5.2"
     id "com.github.hierynomus.license" version "0.14.0"
     id "de.undercouch.download" version "4.1.2"
     id 'org.jetbrains.kotlin.jvm' version '1.4.31'
@@ -110,6 +110,10 @@ dependencies {
     testCompile group: 'junit', name: 'junit', version: '4.12'
     testCompile group: 'org.assertj', name: 'assertj-core', version: '3.11.1'
     testCompile group: 'org.apache.commons', name: 'commons-text', version: '1.9'
+    testImplementation(platform('org.junit:junit-bom:5.8.2'))
+    testImplementation('org.junit.jupiter:junit-jupiter')
+    testImplementation('org.junit.jupiter:junit-jupiter')
+    testRuntimeOnly("org.junit.vintage:junit-vintage-engine")
 }
 
 task libs(type: Sync) {
@@ -159,6 +163,7 @@ task downloadMockJdk8() {
 test.dependsOn( libs, downloadMockJdk7, downloadMockJdk8 )
 
 test {
+    useJUnitPlatform()
     testLogging {
         exceptionFormat = 'full'
     }