First, it should be noted that CFUnit is not intended to be a performance tuning tool. There are other better ways of handling that.
However, it can sometimes be helpful to know which of your tests within a TestCase are running slowly. To do this, simply add the following code to your TestCase:
... <cffunction name="setUp" returntype="void" access="package"> <cfset REQUEST.timer_start = getTickcount()> <!--- Other Setup Code Here ---> </cffunction> <cffunction name="tearDown" returntype="void" access="package"> <!--- Other TearDown Code Here ---> <cfset REQUEST.timer_end = getTickcount()> <cfset REQUEST.timer = REQUEST.timer_end - REQUEST.timer_start> <cftrace var="REQUEST.timer" text="#getString()#"></cftrace> </cffunction> ...You don't need anything else. Next time you run your tests scroll down to the CFML debug output. In the Trace Points you will see a number of lines like this one:
[20:30:44.220 X:\mywebroot\CFUnitExample\TestMyCFC.cfc @ line: 16] [501 ms (1st trace)] - [REQUEST.timer = 70] testMethod(CFUnitExample.TestMyCFC)"REQUEST.timer" equals how long, in milliseconds, each test took to run.