Maybe fix flakey AddRemoveThreepid test (#81)

I have no idea why this is flaking. There are warnings about
things not being wrapped in act() which may be relevant... this makes
the warnings happy, although apparently should not be necessary.
testing-library/user-event#906 and
testing-library/user-event#497 are
depressing reading (making the versions the same didn't help). I think
my conclusion might be to do this until we're able to upgrade to the
latest testing-library, then re-evaluate.

It still may or may not fix the flake.

Author: dbkr

test/components/views/settings/AddRemoveThreepids-test.tsx

@@ -6,7 +6,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
 Please see LICENSE files in the repository root for full details.
 */
 
-import { render, screen } from "@testing-library/react";
+import { render, screen, waitFor } from "@testing-library/react";
 import { MatrixClient, ThreepidMedium } from "matrix-js-sdk/src/matrix";
 import React from "react";
 import userEvent from "@testing-library/user-event";
@@ -218,23 +218,32 @@ describe("AddRemoveThreepids", () => {
         await userEvent.type(input, PHONE1_LOCALNUM);
 
         const addButton = screen.getByRole("button", { name: "Add" });
-        await userEvent.click(addButton);
+        userEvent.click(addButton);
+
+        const continueButton = await screen.findByRole("button", { name: "Continue" });
+
+        await expect(continueButton).toHaveAttribute("aria-disabled", "true");
+
+        await expect(
+            await screen.findByText(
+                `A text message has been sent to +${PHONE1.address}. Please enter the verification code it contains.`,
+            ),
+        ).toBeInTheDocument();
 
         expect(client.requestAdd3pidMsisdnToken).toHaveBeenCalledWith(
             "GB",
             PHONE1_LOCALNUM,
             client.generateClientSecret(),
             1,
         );
-        const continueButton = screen.getByRole("button", { name: "Continue" });
-
-        expect(continueButton).toHaveAttribute("aria-disabled", "true");
 
         const verificationInput = screen.getByRole("textbox", { name: "Verification code" });
         await userEvent.type(verificationInput, "123456");
 
         expect(continueButton).not.toHaveAttribute("aria-disabled", "true");
-        await userEvent.click(continueButton);
+        userEvent.click(continueButton);
+
+        await waitFor(() => expect(continueButton).toHaveAttribute("aria-disabled", "true"));
 
         expect(client.addThreePidOnly).toHaveBeenCalledWith({
             client_secret: client.generateClientSecret(),