anchor.diff:  , pytest
   , testscenarios
   , testtools
  +, unittest2
   }:
   
   buildPythonPackage {
  
positive.code: , cppunit
  , pkg-config
  , subunit
  , pythonAtLeast
  
  # python dependencies
  , fixtures
  
negative.code:   buildInputs = [ check cppunit ];
    propagatedBuildInputs = [ testtools ];
  
    checkInputs = [ testscenarios hypothesis fixtures pytest unittest2 ];
  
    # requires unittest2, which no longer supported in 3.10
    doCheck = pythonOlder "3.10";
    # ignore tests which call shell code, or call methods which haven't been implemented
    checkPhase = ''
      pytest python/subunit \
  