Test_failure</span> <span class="keyword">of</span> string</span></code></div></div><div class="odoc-spec"><div class="spec exception anchored" id="exception-User_error"><a href="#exception-User_error" class="anchor"></a><code><span><span class="keyword">exception</span> </span><span><span class="exception">User_error</span> <span class="keyword">of</span> string</span></code></div></div><div class="odoc-spec"><div class="spec exception anchored" id="exception-Internal_error"><a href="#exception-Internal_er