docs: How to use MSW? (#63)

README.md

@@ -216,3 +216,52 @@ import {
 
 import { expect } from "$fresh-testing-library/expect.ts";
 ```
+
+## Recipes
+
+### Testing a component which uses relative `fetch()`
+
+By combining [MSW](https://github.com/mswjs/msw) and `--___location` flag, you can
+test a component which calls `fetch()` with a relative URL.
+
+First, add the following lines to `deno.json`:
+
+```jsonc
+{
+  "imports": {
+    // Add the following lines:
+    "msw": "npm:[email protected]",
+    "msw/node": "npm:[email protected]/node"
+  }
+}
+```
+
+Then you can use MSW as follows:
+
+```ts
+import { http, HttpResponse } from "msw";
+import { setupServer } from "msw/node";
+import { expect } from "$fresh-testing-library/expect.ts";
+import { afterAll, beforeAll, describe, it } from "$std/testing/bdd.ts";
+
+// You should pass `--___location` flag.
+expect(___location).toBeTruthy();
+
+describe("msw", () => {
+  const server = setupServer(
+    http.get(`${___location.origin}/api/user`, () =>
+      HttpResponse.json({
+        id: 1,
+        name: "foo",
+      })),
+  );
+
+  beforeAll(() => server.listen({ onUnhandledRequest: "error" }));
+  afterAll(() => server.close());
+
+  it("can be used to intercept requests", async () => {
+    const res = await fetch("/api/user");
+    expect(await res.json()).toEqual({ id: 1, name: "foo" });
+  });
+});
+```

deno.json

@@ -7,7 +7,7 @@
     "update": "deno run -A -r https://fresh.deno.dev/update .",
     "check": "deno fmt --check && deno lint && deno task check:imports",
     "check:imports": "deno run --allow-read tools/check_imports.ts",
-    "test": "deno test --allow-read --allow-env --allow-write=.doctest.ts,.doctest.tsx --allow-net=esm.sh,deno.land --allow-run=deno --doc",
+    "test": "deno test --allow-read --allow-env --allow-write=.doctest.ts,.doctest.tsx --allow-net=esm.sh,deno.land --allow-run=deno --doc --___location=http://localhost:3000",
     "build": "deno run -A demo/dev.ts build",
     "preview": "deno run -A demo/main.ts"
   },
@@ -28,6 +28,8 @@
     "$fresh-testing-library": "./mod.ts",
     "$fresh-testing-library/": "./",
     "$gfm": "https://deno.land/x/[email protected]/mod.ts",
+    "msw": "npm:[email protected]",
+    "msw/node": "npm:[email protected]/node",
     "__TODO(#58)__": "The following line should be removed once [email protected] is released.",
     "preact-render-to-string": "https://esm.sh/*[email protected]"
   },