move utils to seperate files and folder, update imports

test/utils/utils.ts

@@ -0,0 +1,11 @@
+/**
+ * Duplicated from Mocha types. TypeScript doesn't infer that type by itself for some reason.
+ */
+export type Done = (err?: any) => void;
+
+export const postJSON = {
+    method: "POST",
+    headers: {
+        "Content-Type": "application/json",
+    },
+};