Add unit test for should_receive function
Add unit test for should_receive function

This adds a comprehensive test for should_receive(). The only part
of the function not covered is the db query on cache miss.

selahssea/ggrc-core,AleksNeStu/ggrc-core,VinnieJohns/ggrc-core,AleksNeStu/ggrc-core,plamut/ggrc-core,plamut/ggrc-core,VinnieJohns/ggrc-core,selahssea/ggrc-core,AleksNeStu/ggrc-core,plamut/ggrc-core,selahssea/ggrc-core,VinnieJohns/ggrc-core,VinnieJohns/ggrc-core,plamut/ggrc-core,selahssea/ggrc-core,AleksNeStu/ggrc-core