beziercurve bz 3 0 0 0 .5 .5e-6 0 1 0 0
mkedge e1 bz 0 .3
mkedge e2 bz .3 0.7
mkedge e3 bz .7 1.
wire w e1 e2 e3
getanacurve c w lin 1.e-3
if {[isdraw c]} {
  set log [dump c]
  if { [regexp {Line} $log ] != 1 } {
     puts "Error: curve is not a line"
  }
} else {
  puts "Error: required curve is not got"
}