Added a java test for tests that aren't legal in kotlin

Author: YetAnotherMatt

builder-processor/build.gradle

@@ -5,4 +5,5 @@ dependencies {
 
     implementation 'com.squareup:kotlinpoet:1.0.0-RC1'
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+    implementation "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"
 }

client/build.gradle

@@ -6,8 +6,10 @@ dependencies {
     kapt project(':builder-processor')
 
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+    implementation "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"
 
     testCompile group: 'org.junit.jupiter', name: 'junit-jupiter-api', version: '5.2.0'
     testCompile group: 'com.willowtreeapps.assertk', name: 'assertk', version: '0.10'
+    testCompile group: 'org.assertj', name: 'assertj-core', version: '3.10.0'
 
 }

client/src/test/java/com/thinkinglogic/example/SimpleDataClassJavaTest.java

@@ -0,0 +1,22 @@
+package com.thinkinglogic.example;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.catchThrowable;
+import static org.assertj.core.api.BDDAssertions.then;
+
+public class SimpleDataClassJavaTest {
+
+    @Test
+    void builderShouldRejectNullValueForRequiredFields() {
+        // given
+        SimpleDataClassBuilder builder = new SimpleDataClassBuilder();
+
+        // when
+        Throwable exception = catchThrowable(() -> builder.notNullString(null));
+
+        then(exception)
+                .isInstanceOf(IllegalArgumentException.class)
+                .hasMessageContaining("notNullString");
+    }
+}