Add tests for Avatar

app/soapbox/components/still_image.js

@@ -54,7 +54,7 @@ class StillImage extends React.PureComponent {
     const hoverToPlay = this.hoverToPlay();
 
     return (
-      <div className={classNames(className, 'still-image', { 'still-image--play-on-hover': hoverToPlay })} style={style}>
+      <div data-testid='still-image-container' className={classNames(className, 'still-image', { 'still-image--play-on-hover': hoverToPlay })} style={style}>
         <img src={src} alt={alt} ref={this.setImageRef} onLoad={this.handleImageLoad} />
         {hoverToPlay && <canvas ref={this.setCanvasRef} />}
       </div>

app/soapbox/components/ui/avatar/__tests__/avatar.test.tsx

@@ -0,0 +1,20 @@
+import React from 'react';
+
+import { render, screen } from '../../../../jest/test-helpers';
+import Avatar from '../avatar';
+
+const src = '/static/alice.jpg';
+
+describe('<Avatar />', () => {
+  it('renders', () => {
+    render(<Avatar src={src} />);
+
+    expect(screen.getByRole('img')).toBeInTheDocument();
+  });
+
+  it('handles size props', () => {
+    render(<Avatar src={src} size={50} />);
+
+    expect(screen.getByTestId('still-image-container').getAttribute('style')).toMatch(/50px/i);
+  });
+});