add an example test

src/tests/__tests__/example/use-fetch.spec.ts

@@ -0,0 +1,47 @@
+import { ref } from "vue";
+import { describe, it, expect, vi, afterEach } from "vitest";
+import { useFetch } from "@vueuse/core";
+
+global.fetch = vi.fn();
+
+// https://runthatline.com/how-to-mock-fetch-api-with-vitest/
+// https://vueuse.org/core/useFetch/
+
+describe("useFetch", () => {
+  type Response = Awaited<ReturnType<typeof global.fetch>>;
+
+  // @ts-expect-error
+  const createResponse = (data: any): Response => ({
+    json: () => new Promise((resolve) => resolve(data)),
+    ok: true, // https://github.com/vueuse/vueuse/blob/v10.4.1/packages/core/useFetch/index.ts#L471
+  });
+
+  const responseData = [
+    {
+      title: "Unit test",
+      done: false,
+    },
+  ];
+
+  afterEach(() => {
+    vi.mocked(global.fetch).mockReset();
+  });
+
+  it("should work", async () => {
+    vi.mocked(fetch).mockResolvedValue(createResponse(responseData));
+
+    const url = ref("https://jsonplaceholder.typicode.com/todos/1");
+
+    const { data, isFinished, then } = useFetch(url, {
+      refetch: true,
+    }).json();
+
+    expect(isFinished.value).toBe(false);
+    expect(data.value).toBeNull();
+    await then();
+    expect(isFinished.value).toBe(true);
+    expect(data.value).toStrictEqual(responseData);
+
+    // console.log(global.fetch.mock.calls);
+  });
+});