pythonPackages.gprof2dot: enable tests

pkgs/development/python-modules/gprof2dot/default.nix

@@ -1,4 +1,4 @@
-{ lib, fetchFromGitHub, buildPythonApplication }:
+{ lib, fetchFromGitHub, buildPythonApplication, python, graphviz }:
 
 buildPythonApplication {
   name = "gprof2dot-2017-09-19";
@@ -10,6 +10,9 @@ buildPythonApplication {
     sha256 = "1b5wvjv5ykbhz7aix7l3y7mg1hxi0vgak4a49gr92sdlz8blj51v";
   };
 
+  checkInputs = [ graphviz ];
+  checkPhase = "${python.interpreter} tests/test.py";
+
   meta = with lib; {
     homepage = https://github.com/jrfonseca/gprof2dot;
     description = "Python script to convert the output from many profilers into a dot graph";