test: add fetch util tests

Author: janniks

packages/common/tests/fetchUtil.test.ts

@@ -0,0 +1,76 @@
+import fetchMock from 'jest-fetch-mock';
+import { createApiKeyMiddleware, createFetchFn, FetchMiddleware, RequestContext } from '../src';
+
+describe('fetch middleware', () => {
+  test('createApiKeyMiddleware adds x-api-key header to correct host request', async () => {
+    const apiKey = 'MY_KEY';
+
+    const middleware = createApiKeyMiddleware({ apiKey });
+    expect(middleware.pre).not.toBeNull();
+
+    const fetchFn = createFetchFn(middleware);
+
+    await fetchFn('https://example.com');
+    expect(fetchMock.mock.calls[0][1]?.headers).toBe(undefined);
+
+    await fetchFn('https://api.stacks.co');
+    expect(fetchMock.mock.calls[1][1]?.headers).toBeDefined();
+    expect((fetchMock.mock.calls[1][1]?.headers as Headers)?.get('x-api-key')).toContain(apiKey);
+  });
+
+  test('middleware calls pre and post', async () => {
+    const preMiddleware = jest.fn(() => undefined as void);
+    const postMiddleware = jest.fn(() => undefined as void);
+
+    const middleware = {
+      pre: preMiddleware,
+      post: postMiddleware,
+    } as FetchMiddleware;
+
+    const fetchFn = createFetchFn(middleware);
+    await fetchFn('https://example.com');
+
+    expect(preMiddleware.mock.calls.length).toBe(1);
+    expect(postMiddleware.mock.calls.length).toBe(1);
+  });
+
+  test.each(['pre', 'post'])('middleware chains pass state', async hook => {
+    const middleware1 = jest.fn((ctx: RequestContext) => {
+      ctx.init.headers = new Headers();
+      ctx.init.headers.set('foo', 'bar');
+      return ctx;
+    });
+    const middleware2 = jest.fn((ctx: RequestContext) => {
+      expect((ctx.init.headers as Headers).get('foo')).toBe('bar');
+      (ctx.init.headers as Headers).set('foo', 'bla');
+      // should also work if middleware doesn't return context
+    });
+    const middleware3 = jest.fn((ctx: RequestContext) => {
+      expect((ctx.init.headers as Headers).get('foo')).toBe('bla');
+      (ctx.init.headers as Headers).set('foo', 'baz');
+      return ctx;
+    });
+
+    const fetchFn = createFetchFn(
+      {
+        [hook]: middleware1,
+      },
+      {
+        [hook]: middleware2,
+      },
+      {
+        [hook]: middleware3,
+      }
+    );
+
+    fetchMock.mockOnce('*', { status: 200 });
+    const res = await fetchFn('https://httpstat.us/202');
+    console.log(res);
+
+    expect((fetchMock.mock.calls[0][1]?.headers as Headers).get('foo')).toBe('baz');
+
+    expect(middleware1.mock.calls.length).toBe(1);
+    expect(middleware2.mock.calls.length).toBe(1);
+    expect(middleware3.mock.calls.length).toBe(1);
+  });
+});