Apply Kotlin plugin to test project, store versions in root build.gradle.

Author: greenrobot-team

build.gradle

@@ -28,12 +28,22 @@ buildscript {
         objectboxNativeDependency = "io.objectbox:objectbox-$objectboxPlatform:$ob_native_version"
         println "ObjectBox native dependency: $objectboxNativeDependency"
     }
+
+    ext.kotlin_version = '1.3.61'
+    ext.dokka_version = '0.10.1'
     ext.junit_version = '4.13'
 
     repositories {
         mavenCentral()
         jcenter()
     }
+
+    dependencies {
+        // Add Kotlin plugins once. Apply in sub-projects as required.
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+        classpath "org.jetbrains.dokka:dokka-gradle-plugin:$dokka_version"
+    }
+
 }
 
 allprojects {

objectbox-kotlin/build.gradle

@@ -3,18 +3,6 @@ version= rootProject.version
 
 buildscript {
     ext.javadocDir = "$buildDir/docs/javadoc"
-    ext.kotlin_version = '1.3.61'
-    ext.dokka_version = '0.10.1'
-
-    repositories {
-        mavenCentral()
-        jcenter()
-    }
-
-    dependencies {
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath "org.jetbrains.dokka:dokka-gradle-plugin:$dokka_version"
-    }
 }
 
 apply plugin: 'kotlin'

tests/objectbox-java-test/build.gradle

@@ -1,4 +1,5 @@
 apply plugin: 'java'
+apply plugin: 'kotlin'
 
 uploadArchives.enabled = false
 
@@ -23,6 +24,7 @@ repositories {
 
 dependencies {
     compile project(':objectbox-java')
+    compile project(':objectbox-kotlin')
     compile 'org.greenrobot:essentials:3.0.0-RC1'
 
     // Check flag to use locally compiled version to avoid dependency cycles