# odetest(solution, eq) is to test solution for eq if it gives 0;
# f:= 2y+1, eq:=y'-f=0,  s:=dsolve(eq), odetest(s, eq);
# f:= 2y+1, eq:=ds(y,x,0.5)-f=0,  s:=dsolve(eq), odetest(s, eq);

odetest(sol_, l_=r_,y_, x0_):= n(replace(value(replace(replace(l-r,y',d(sol)),y,sol)),x,x0));
odetest(sol_, l_=r_,y_):= n(replace(value(replace(replace(l-r,y',d(sol)),y,sol)),x,1.1));
odetest(sol_, l_=r_):= n(expand(value(replace(replace(l-r,y',d(sol)),y,sol))));
odetest(yy_=sol_, eq1_=eq2_):=n((yy=sol)-(dsolve(eq1=eq2)));
odetest(yy_=sol_, eq1_=eq2_,y_):=n((yy=sol)-(dsolve(eq1=eq2,y)));
odetest(s_,s_):=0;