added tests for function_range method
added tests for function_range method

chaffra/sympy,madan96/sympy,souravsingh/sympy,aktech/sympy,kaushik94/sympy,kaushik94/sympy,yashsharan/sympy,kaushik94/sympy,jaimahajan1997/sympy,souravsingh/sympy,chaffra/sympy,aktech/sympy,skidzo/sympy,souravsingh/sympy,skidzo/sympy,postvakje/sympy,drufat/sympy,sampadsaha5/sympy,drufat/sympy,rahuldan/sympy,jaimahajan1997/sympy,madan96/sympy,postvakje/sympy,rahuldan/sympy,drufat/sympy,sampadsaha5/sympy,postvakje/sympy,jaimahajan1997/sympy,yashsharan/sympy,yashsharan/sympy,chaffra/sympy,rahuldan/sympy,sampadsaha5/sympy,aktech/sympy,skidzo/sympy,madan96/sympy