[ For people not aware of Hapao: Hapao is a visual test coverage tool for Pharo. More info on: http://bergel.eu/download/papers/Berg12c-HapaoSCP.pdf ] Hi Sheridan, How did you load Hapao? Roassal seems to be missing. The following should work: Gofer it smalltalkhubUser: 'ObjectProfile' project: 'Spy2'; configurationOf: 'Spy2'; loadStable. I can get the coverage of the class String. Here is the result by the way: https://dl.dropboxusercontent.com/u/31543901/TMP/StringCoverage/index.html Interesting to see that, despite all the unit test that uses String, String is not even 50% covered. I have attached the html coverage report to this email. Cheers, Alexandre