refactor: move from groovy to java migration (#7)

.travis.yml

@@ -1,17 +1,17 @@
-language: groovy
+language: java
 
 jdk:
-    - oraclejdk8
-    - oraclejdk9
-    - oraclejdk10
-    - openjdk8
+- oraclejdk8
+- oraclejdk9
+- oraclejdk10
+- openjdk8
 
 before_script:
-    - chmod +x gradlew
+- chmod +x gradlew
 
 script:
-    - ./gradlew check
-    - ./gradlew jacocoTestReport
+- ./gradlew check
+- ./gradlew jacocoTestReport
 
 after_success:
-    - bash <(curl -s https://codecov.io/bash)
+- bash <(curl -s https://codecov.io/bash)

build.gradle

@@ -1,14 +1,16 @@
 plugins {
-    id 'groovy'
     id 'maven'
     id 'jacoco'
 }
 
+apply plugin: 'java'
+
 group 'org.arkecosystem.client'
 version '0.1.0'
 
 repositories {
     jcenter()
+    mavenCentral()
 }
 
 task createPom {
@@ -30,16 +32,20 @@ task createPom {
 }
 
 dependencies {
-    compile group: 'org.codehaus.groovy', name: 'groovy-all', version: '2.5.1'
     compile group: 'com.squareup.okhttp3', name: 'okhttp', version: '3.11.0'
     compile group: 'com.squareup.okhttp3', name: 'mockwebserver', version: '3.11.0'
     compile group: 'com.google.code.gson', name: 'gson', version: '2.8.5'
 
-    testCompile group: 'org.spockframework', name: 'spock-core', version: '1.1-groovy-2.4'
-    testCompile group: 'junit', name: 'junit', version: '4.12'
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.3.1'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.3.1'
+}
 
-    // Build blows up without this?
-    compile group: 'javax.xml.bind', name: 'jaxb-api', version: '2.3.0'
+test {
+    useJUnitPlatform()
+    failFast = true
+    testLogging {
+        events 'PASSED', 'FAILED', 'SKIPPED'
+    }
 }
 
 jacocoTestReport {