1 files changed, 68 insertions, 1 deletions

diff --git a/yamn/encoder/encoder_test.go b/yamn/encoder/encoder_test.go
index 3509070..333b704 100644
--- a/yamn/encoder/encoder_test.go
+++ b/yamn/encoder/encoder_test.go
@@ -57,16 +57,83 @@ func TestValidateUsenetRequiresGatewayRecipient(t *testing.T) {
 func TestComposeUsenetGatewayHeaders(t *testing.T) {
 	plain, err := composeMessage(Request{
 		Kind: Usenet, To: "mail2news@example.org", Subject: "test", Newsgroup: "misc.test", Body: "hello",
+		References: "<parent@example.org>",
 	})
 	if err != nil {
 		t.Fatal(err)
 	}
 	text := string(plain)
-	if !strings.Contains(text, "To: mail2news@example.org\n") || !strings.Contains(text, "Newsgroups: misc.test\n") {
+	if !strings.Contains(text, "To: mail2news@example.org\n") ||
+		!strings.Contains(text, "Newsgroups: misc.test\n") ||
+		!strings.Contains(text, "References: <parent@example.org>\n") ||
+		!strings.Contains(text, "In-Reply-To: <parent@example.org>\n") {
 		t.Fatalf("missing Usenet delivery headers: %q", text)
 	}
 }
 
+func TestComposeReferencesChainUsesLastIDAsParent(t *testing.T) {
+	plain, err := composeMessage(Request{
+		Kind: Usenet, To: "mail2news@example.org", Subject: "test", Newsgroup: "misc.test", Body: "hello",
+		References: "  <root@example.org>   <parent@example.org>  ",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	text := string(plain)
+	if !strings.Contains(text, "References: <root@example.org> <parent@example.org>\n") ||
+		!strings.Contains(text, "In-Reply-To: <parent@example.org>\n") {
+		t.Fatalf("thread headers were not normalized: %q", text)
+	}
+}
+
+func TestValidateReferences(t *testing.T) {
+	tests := []struct {
+		name       string
+		references string
+		valid      bool
+	}{
+		{name: "empty", valid: true},
+		{name: "whitespace only", references: "   "},
+		{name: "parent", references: "<parent@example.org>", valid: true},
+		{name: "thread chain", references: "<root@example.org> <parent@example.org>", valid: true},
+		{name: "missing brackets", references: "parent@example.org"},
+		{name: "missing local part", references: "<@example.org>"},
+		{name: "multiple at signs", references: "<parent@example@org>"},
+		{name: "embedded newline", references: "<root@example.org>\n<parent@example.org>"},
+		{name: "header label", references: "References: <parent@example.org>"},
+		{name: "too long", references: "<" + strings.Repeat("a", maxReferencesBytes) + "@example.org>"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			request := Request{
+				Kind: Email, PublicKeyring: "/tmp/pubring.mix", Entry: "entry", Chain: []string{"entry"},
+				To: "user@example.org", Body: "hello", References: test.references,
+			}
+			err := Validate(request)
+			if test.valid && err != nil {
+				t.Fatalf("expected valid References, got %v", err)
+			}
+			if !test.valid && err == nil {
+				t.Fatal("expected invalid References to be rejected")
+			}
+		})
+	}
+}
+
+func TestValidateReplyTo(t *testing.T) {
+	request := Request{
+		Kind: Email, PublicKeyring: "/tmp/pubring.mix", Entry: "entry", Chain: []string{"entry"},
+		To: "user@example.org", Body: "hello", ReplyTo: "Pseudonym <reply@example.org>",
+	}
+	if err := Validate(request); err != nil {
+		t.Fatalf("expected valid Reply-To, got %v", err)
+	}
+	request.ReplyTo = "not an address"
+	if err := Validate(request); err == nil {
+		t.Fatal("expected invalid Reply-To to be rejected")
+	}
+}
+
 func TestEncodeProducesYAMNArmor(t *testing.T) {
 	keyring := testKeyring(t)
 	result, err := Encode(Request{