title: Pandas unit testing: How to assert equality of NaT and NaN values?
body: <p>In NumPy and Pandas, <code>nan != nan</code> and <code>NaT != NaT</code>. So, when comparing results during unit testing, how can I assert that a returned value is one of those values? A simple <code>assertEqual</code> naturally fails, even if I use <code>pandas.util.testing</code>.</p>