func TestSf(t *testing.T) {
var x float64 = 5.0
var result sf.GslSfResult
expected := -0.17759677131433830434739701
status := bessel.J0E(x, &result)
fmt.Printf("status = %s\n", gogsl.GslError(status).String())
fmt.Printf("J0(5.0) = %.18f\n"+
" +/- % .18f\n", result.Val(), result.Err())
fmt.Printf("exact = %.18f\n", expected)
if math.Abs(result.Val()-expected) > result.Err() {
t.Error("incorrect value")
}
}