dns/dnsmessage: improve test coverage of skipping

Updates golang/go#16218 Change-Id: I613cf0a65d40a9823c83e0a547fbd48b2236d16e Reviewed-on: https://go-review.googlesource.com/49630 Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com> Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>

Author: iangudger

dns/dnsmessage/message_test.go

@@ -277,6 +277,69 @@ func TestSkipAll(t *testing.T) {
 }
 }
 
+func TestSkipEach(t *testing.T) {
+msg := smallTestMsg()
+
+buf, err := msg.Pack()
+if err != nil {
+t.Fatal("Packing test message:", err)
+}
+var p Parser
+if _, err := p.Start(buf); err != nil {
+t.Fatal(err)
+}
+
+tests := []struct {
+name string
+f func() error
+}{
+{"SkipQuestion", p.SkipQuestion},
+{"SkipAnswer", p.SkipAnswer},
+{"SkipAuthority", p.SkipAuthority},
+{"SkipAdditional", p.SkipAdditional},
+}
+for _, test := range tests {
+if err := test.f(); err != nil {
+t.Errorf("First call: got %s() = %v, want = %v", test.name, err, nil)
+}
+if err := test.f(); err != ErrSectionDone {
+t.Errorf("Second call: got %s() = %v, want = %v", test.name, err, ErrSectionDone)
+}
+}
+}
+
+func TestSkipAfterRead(t *testing.T) {
+msg := smallTestMsg()
+
+buf, err := msg.Pack()
+if err != nil {
+t.Fatal("Packing test message:", err)
+}
+var p Parser
+if _, err := p.Start(buf); err != nil {
+t.Fatal(err)
+}
+
+tests := []struct {
+name string
+skip func() error
+read func() error
+}{
+{"Question", p.SkipQuestion, func() error { _, err := p.Question(); return err }},
+{"Answer", p.SkipAnswer, func() error { _, err := p.Answer(); return err }},
+{"Authority", p.SkipAuthority, func() error { _, err := p.Authority(); return err }},
+{"Additional", p.SkipAdditional, func() error { _, err := p.Additional(); return err }},
+}
+for _, test := range tests {
+if err := test.read(); err != nil {
+t.Errorf("Got %s() = _, %v, want = _, %v", test.name, err, nil)
+}
+if err := test.skip(); err != ErrSectionDone {
+t.Errorf("Got Skip%s() = %v, want = %v", test.name, err, ErrSectionDone)
+}
+}
+}
+
 func TestSkipNotStarted(t *testing.T) {
 var p Parser
 
@@ -745,6 +808,50 @@ func BenchmarkBuilding(b *testing.B) {
 }
 }
 
+func smallTestMsg() Message {
+name := mustNewName("example.com.")
+return Message{
+Header: Header{Response: true, Authoritative: true},
+Questions: []Question{
+{
+Name: name,
+Type: TypeA,
+Class: ClassINET,
+},
+},
+Answers: []Resource{
+{
+ResourceHeader{
+Name: name,
+Type: TypeA,
+Class: ClassINET,
+},
+&AResource{[4]byte{127, 0, 0, 1}},
+},
+},
+Authorities: []Resource{
+{
+ResourceHeader{
+Name: name,
+Type: TypeA,
+Class: ClassINET,
+},
+&AResource{[4]byte{127, 0, 0, 1}},
+},
+},
+Additionals: []Resource{
+{
+ResourceHeader{
+Name: name,
+Type: TypeA,
+Class: ClassINET,
+},
+&AResource{[4]byte{127, 0, 0, 1}},
+},
+},
+}
+}
+
 func largeTestMsg() Message {
 name := mustNewName("foo.bar.example.com.")
 return Message{