Formatting and testing

src/wait.ts

@@ -0,0 +1,12 @@
+/**
+ * Wait for a number of milliseconds. Resolves with 'done!' after the wait time.
+ */
+export async function wait(milliseconds: number): Promise<string> {
+  return new Promise(resolve => {
+    if (isNaN(milliseconds)) {
+      throw new Error('milliseconds not a number')
+    }
+
+    setTimeout(() => resolve('done!'), milliseconds)
+  })
+}