Most of the refactor. Need to switch machines.

crates/core/assets/Main.java

@@ -0,0 +1,10 @@
+public class Main {
+
+    public static void main(String[] args) {
+        System.out.println("Hello, world!");
+    }
+
+    public static int add(int a, int b) {
+        return a + b;
+    }
+}

crates/core/assets/MainTest.java

@@ -0,0 +1,10 @@
+public class MainTest {
+
+    public static void main(String[] args) {
+        testAdd();
+    }
+
+    public static void testAdd() {
+        assert Main.add(2, 2) == 4;
+    }
+}