func TestSetIsEmpty(t *testing.T) {
	if !(Set{}).AsSelector().Empty() {
		t.Errorf("Empty set should be empty")
	}
	if !(NewSelector()).Empty() {
		t.Errorf("Nil Selector should be empty")
	}
}

func TestLexer(t *testing.T) {
	testcases := []struct {
		s string
		t Token
	}{
		{"", EndOfStringToken},
		{",", CommaToken},
		{"notin", NotInToken},
		{"in", InToken},
		{"=", EqualsToken},