ce = { 1, 3, 7, 9, 10 };     <br />&#160;&#160;&#160; Func&lt;<span class="ValueType">int</span>, <span class="ValueType">bool</span>&gt; predicate = <span class="Keyword">null</span>;     <br />&#160;&#160;&#160; Assert.Throws&lt;ArgumentNullException&gt;(() =&gt; source.Where(predicate));     <br />} </div>  <p>I&#39;m not bothering to check the name within the ArgumentNullException, but importantly I&#39;m testing that the arguments are being validated immediately. I&#39;m not trying to iterate over the 