add e2e test for env vars

Author: james-elicx

examples/api/.dev.vars

@@ -0,0 +1 @@
+NEXTJS_ENV=development

examples/api/.env.development

@@ -0,0 +1 @@
+TEST_ENV_VAR=TEST_VALUE

examples/api/app/api/env/route.ts

@@ -0,0 +1,3 @@
+export async function GET() {
+  return new Response(JSON.stringify(process.env));
+}

examples/api/e2e/base.spec.ts

@@ -30,3 +30,8 @@ test("the hello-world api POST route works as intended", async ({ page }) => {
   expect(res.headers()["content-type"]).toContain("text/plain");
   await expect(res.text()).resolves.toEqual("Hello post-World! body=some body");
 });
+
+test("sets environment variables from the Next.js env file", async ({ page }) => {
+  const res = await page.request.get("/api/env");
+  expect(res.json()).toContain({ TEST_ENV_VAR: "TEST_VALUE" });
+});