private static void AssertExpression(string content, string expected, int index = -1, PythonLanguageVersion version = PythonLanguageVersion.V35)
{
var buffer = new MockTextBuffer(content);
if (index < 0)
{
index += content.Length + 1;
}
var span = new SnapshotSpan(buffer.CurrentSnapshot, index, 0);
var actual = PythonTextBufferInfo.GetExpressionAtPoint(span, version, GetExpressionOptions.Hover);
Assert.AreEqual(expected, actual?.GetText(), content);
}