Ratchet up Component test coverage

Turns out a number of our components are a pain to run via a mounting
test, but Svelte does suggest that this is the dispreferred way to test
anyway. Using use:, triggering navigation after logout, and
scrollIntoView all make the headless node test process with the janky
in-memory mount have a Very Bad Day.

But this is still progress! We will press on.

1 files changed, 44 insertions, 5 deletions

diff --git a/ui/tests/lib/components/MessageInput.svelte.test.js b/ui/tests/lib/components/MessageInput.svelte.test.js
index 597f0c3..d90026c 100644
--- a/ui/tests/lib/components/MessageInput.svelte.test.js
+++ b/ui/tests/lib/components/MessageInput.svelte.test.js
@@ -1,9 +1,48 @@
-// async onSubmit(event)
-// onKeyDown(event)
-import { describe, expect, test } from 'vitest';
+import { flushSync, mount, unmount } from 'svelte';
+import { afterEach, beforeEach, describe, expect, test, vi } from 'vitest';
+import MessageInput from '$lib/components/MessageInput.svelte';
+import axios from 'axios';
+
+let component;
+
+let mocks = vi.hoisted(() => ({
+  post: vi.fn(),
+}));
 
 describe('MessageInput', () => {
-  test('stub', async () => {
-    expect(true).toBeTruthy();
+  beforeEach(() => {
+    vi.mock('axios', async (importActual) => {
+      const actual = await importActual();
+
+      const mockAxios = {
+        default: {
+          ...actual.default,
+          create: vi.fn(() => ({
+            ...actual.default.create(),
+            post: mocks.post,
+          })),
+        },
+      };
+
+      return mockAxios;
+    });
+    mocks.post.mockResolvedValue({ status: 200 });
+
+    component = mount(MessageInput, {
+      target: document.body, // `document` exists because of jsdom
+    });
+    flushSync();
+  });
+
+  afterEach(() => {
+    unmount(component);
+  });
+
+  test('onsubmit happy path', async () => {
+    // Click the button, then flush the changes so you can synchronously write expectations
+    document.body.querySelector('button[type=submit]').click();
+    flushSync();
+
+    expect(mocks.post).toHaveBeenCalled();
   });
 });