Added a decorator for marking methods as stubs.

src/core/decorators.ts

@@ -0,0 +1,17 @@
+/**
+ * Prints a warning when the method is called.
+ */
+export const stub: MethodDecorator = function stub(
+    target: Object,
+    prop_key: PropertyKey,
+    descriptor: PropertyDescriptor,
+) {
+    const orig_method: Function = descriptor.value;
+
+    descriptor.value = function(...args: any[]): any {
+        console.warn(`Stub: ${target.constructor.name}.prototype.${String(prop_key)}`);
+        return orig_method.apply(this, args);
+    };
+
+    return descriptor;
+};