This test was probably intended to be

      <test>format-number(1e0 div 0e0,'#############')</test>

since (decimal) 1.0 div 0.0 is an error, not NaN.

  <test-case name="numberformatNaN">
      <description>
        Creator: Zhen Hua Liu
        Purpose: NaN input from 1.0 div 0.0. </description>
      <created by="Zhen Hua Liu" on="2012-01-18"/>
      <environment/>
      <test>format-number(1.0 div 0.0,'#############')</test>
      <result>
         <assert-string-value>NaN</assert-string-value>
      </result>
   </test-case>