add: unit and integration testing

app/node_modules/collect-v8-coverage/index.d.ts

@@ -0,0 +1,7 @@
+/// <reference types="node" />
+import { Profiler } from 'inspector';
+export declare type V8Coverage = ReadonlyArray<Profiler.ScriptCoverage>;
+export declare class CoverageInstrumenter {
+  startInstrumenting(): Promise<void>;
+  stopInstrumenting(): Promise<V8Coverage>;
+}