Add some expression unit tests
Add some expression unit tests

GtTmy/pyeda,sschnug/pyeda,sschnug/pyeda,sschnug/pyeda,cjdrake/pyeda,GtTmy/pyeda,GtTmy/pyeda,pombredanne/pyeda,cjdrake/pyeda,karissa/pyeda,cjdrake/pyeda,pombredanne/pyeda,karissa/pyeda,karissa/pyeda,pombredanne/pyeda