title: XCTestCase - how to assert on a NSTextView containing String?
body: <p>I have a macOS project that I'm creating UI tests for.</p>
  
  <p>While it's relatively easy to find <code>staticText</code>, <code>buttons</code>, etc. by their text value.  Using a subscript lookup on <code>.textViews</code> doesn't (seem to) work.</p>
  
  <p>I've managed to get a reference to the <code>NSTextView</code> I want to inspect using <code>.textViews.firstMatch</code> but I can't figure out how to assert on it's string value.</p>
  
  <p>I'm looking for something that works like this.</p>
  
  <pre><code>XCTAssertEqual(prefs.textViews.firstMatch.stringValue, "Enter text below")
  </code></pre>