Fix unit tests and correct several issues with hinting.

The packet registry tests are defunct, and will be rewritten at a future date.

native/build.gradle

@@ -21,6 +21,10 @@ dependencies {
     testImplementation "org.junit.jupiter:junit-jupiter-engine:${junitVersion}"
 }
 
+test {
+    useJUnitPlatform()
+}
+
 publishing {
     publications {
         mavenJava(MavenPublication) {