1 files changed, 32 insertions, 0 deletions
diff --git a/internal/server/handlers/protocol_codec_test.go b/internal/server/handlers/protocol_codec_test.go
new file mode 100644
index 0000000..a182d18
--- /dev/null
+++ b/internal/server/handlers/protocol_codec_test.go
@@ -0,0 +1,32 @@
+package handlers
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/mimecast/dtail/internal/protocol"
+)
+
+func TestHandleProtocolVersionUsesSemanticCompatComparison(t *testing.T) {
+	codec := newProtocolCodec(nil)
+
+	args, argc, add, err := codec.handleProtocolVersion([]string{"protocol", "4", "tail", "payload"})
+	if err == nil {
+		t.Fatal("expected protocol mismatch error")
+	}
+	if argc != 4 {
+		t.Fatalf("unexpected argc: got %d want 4", argc)
+	}
+	if len(args) != 4 || args[0] != "protocol" || args[1] != "4" {
+		t.Fatalf("unexpected args returned: %#v", args)
+	}
+	if add != "" {
+		t.Fatalf("unexpected message separator: %q", add)
+	}
+	if !strings.Contains(err.Error(), "please update DTail client") {
+		t.Fatalf("expected client update guidance, got %q", err)
+	}
+	if !strings.Contains(err.Error(), protocol.ProtocolCompat) {
+		t.Fatalf("expected error to mention server protocol version, got %q", err)
+	}
+}