 class="na">run</span><span class="p">(</span><span class="s1">&#39;Foo&#39;</span><span class="p">,</span> <span class="s1">&#39;is_string&#39;</span><span class="p">);</span>
</pre></div>
</div>
<p>Notice the use of “is_string” in the second parameter? This tells the
function to evaluate whether your test is producing a string as the
result. Here is a list of allowed comparison types:</p>
<ul class="simple">
<li>is_object</li>
<li>is_string</li>
<li>is_bool</li>
<li>is_true</li>
<li>is_false</li>
<li>