Add helpers to wait for axios requests

Add two methods to the axios_utils Jest mock:

- `waitFor(url)`, which returns a Promise that resolves when the
  next request to `url` finishes.
- `waitForAll()`, which returns a Promise that resolves when all
  pending requests finish.

1 files changed, 45 insertions, 0 deletions

diff --git a/spec/frontend/lib/utils/axios_utils_spec.js b/spec/frontend/lib/utils/axios_utils_spec.js
new file mode 100644
index 00000000000..d5c39567f06
--- /dev/null
+++ b/spec/frontend/lib/utils/axios_utils_spec.js
@@ -0,0 +1,45 @@
+/* eslint-disable promise/catch-or-return */
+
+import AxiosMockAdapter from 'axios-mock-adapter';
+
+import axios from '~/lib/utils/axios_utils';
+
+describe('axios_utils', () => {
+  let mock;
+
+  beforeEach(() => {
+    mock = new AxiosMockAdapter(axios);
+    mock.onAny('/ok').reply(200);
+    mock.onAny('/err').reply(500);
+    expect(axios.countActiveRequests()).toBe(0);
+  });
+
+  afterEach(() => axios.waitForAll().finally(() => mock.restore()));
+
+  describe('waitForAll', () => {
+    it('resolves if there are no requests', () => axios.waitForAll());
+
+    it('waits for all requests to finish', () => {
+      const handler = jest.fn();
+      axios.get('/ok').then(handler);
+      axios.get('/err').catch(handler);
+
+      return axios.waitForAll().finally(() => {
+        expect(handler).toHaveBeenCalledTimes(2);
+        expect(handler.mock.calls[0][0].status).toBe(200);
+        expect(handler.mock.calls[1][0].response.status).toBe(500);
+      });
+    });
+  });
+
+  describe('waitFor', () => {
+    it('waits for requests on a specific URL', () => {
+      const handler = jest.fn();
+      axios.get('/ok').finally(handler);
+      axios.waitFor('/err').finally(() => {
+        throw new Error('waitFor on /err should not be called');
+      });
+      return axios.waitFor('/ok');
+    });
+  });
+});