Tests for Page404 (#646)

* test: add tests for Page404

* fix: fix typo

src/old/lib/components/Errors/Page404.test.tsx

@@ -0,0 +1,10 @@
+import React from 'react';
+import { render } from '@testing-library/react';
+import Page404 from './Page404';
+
+describe('Page404', () => {
+  it('should render component and match snapshot', () => {
+    const { asFragment } = render(<Page404 />);
+    expect(asFragment()).toMatchSnapshot();
+  });
+});

src/old/lib/components/Errors/__snapshots__/Page404.test.tsx.snap

@@ -0,0 +1,15 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Page404 should render component and match snapshot 1`] = `
+<DocumentFragment>
+  <div
+    style="margin: auto;"
+  >
+    <h1
+      class="MuiTypography-root MuiTypography-h1 MuiTypography-alignCenter"
+    >
+      На жаль, таку сторінку не знайдено.
+    </h1>
+  </div>
+</DocumentFragment>
+`;