rpcclient: add tests for DisableAuth header behavior

Add table-driven tests that verify:
- Authorization header is omitted when DisableAuth is true
- Authorization header is present when DisableAuth is false
- Default (zero value) behavior includes Authorization header

Suggested by @TechLateef in #2514.

rpcclient/disableauth_test.go

@@ -0,0 +1,109 @@
+package rpcclient
+
+import (
+	"encoding/base64"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestDisableAuth verifies that the DisableAuth field correctly controls
+// whether the Authorization header is sent on RPC requests.
+func TestDisableAuth(t *testing.T) {
+	t.Parallel()
+
+	t.Run("DisableAuth true omits Authorization header", func(t *testing.T) {
+		t.Parallel()
+
+		var gotAuth string
+		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			gotAuth = r.Header.Get("Authorization")
+			// Return a valid JSON-RPC response so the client doesn't retry.
+			w.Header().Set("Content-Type", "application/json")
+			w.Write([]byte(`{"result":null,"error":null,"id":1}`))
+		}))
+		defer srv.Close()
+
+		addr := strings.TrimPrefix(srv.URL, "http://")
+		client, err := New(&ConnConfig{
+			Host:        addr,
+			HTTPPostMode: true,
+			DisableAuth: true,
+			DisableTLS:  true,
+		}, nil)
+		require.NoError(t, err)
+		defer client.Shutdown()
+
+		// The client is now connected; issue a simple request to trigger
+		// handleSendPostMessage.
+		_, err = client.RawRequest("getblockchaininfo", nil)
+		// We don't care if the RPC itself errors — we only care about
+		// the Authorization header.
+		_ = err
+
+		require.Empty(t, gotAuth, "Authorization header should be empty when DisableAuth is true")
+	})
+
+	t.Run("DisableAuth false includes Authorization header", func(t *testing.T) {
+		t.Parallel()
+
+		var gotAuth string
+		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			gotAuth = r.Header.Get("Authorization")
+			w.Header().Set("Content-Type", "application/json")
+			w.Write([]byte(`{"result":null,"error":null,"id":1}`))
+		}))
+		defer srv.Close()
+
+		addr := strings.TrimPrefix(srv.URL, "http://")
+		client, err := New(&ConnConfig{
+			Host:        addr,
+			HTTPPostMode: true,
+			DisableAuth: false,
+			DisableTLS:  true,
+			User:        "testuser",
+			Pass:        "testpass",
+		}, nil)
+		require.NoError(t, err)
+		defer client.Shutdown()
+
+		_, err = client.RawRequest("getblockchaininfo", nil)
+		_ = err
+
+		expected := "Basic " + base64.StdEncoding.EncodeToString([]byte("testuser:testpass"))
+		require.Equal(t, expected, gotAuth, "Authorization header should be set when DisableAuth is false")
+	})
+
+	t.Run("DisableAuth default (zero value) includes Authorization header", func(t *testing.T) {
+		t.Parallel()
+
+		var gotAuth string
+		srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			gotAuth = r.Header.Get("Authorization")
+			w.Header().Set("Content-Type", "application/json")
+			w.Write([]byte(`{"result":null,"error":null,"id":1}`))
+		}))
+		defer srv.Close()
+
+		addr := strings.TrimPrefix(srv.URL, "http://")
+		client, err := New(&ConnConfig{
+			Host:        addr,
+			HTTPPostMode: true,
+			// DisableAuth left as default (false)
+			DisableTLS:  true,
+			User:        "myuser",
+			Pass:        "mypass",
+		}, nil)
+		require.NoError(t, err)
+		defer client.Shutdown()
+
+		_, err = client.RawRequest("getblockchaininfo", nil)
+		_ = err
+
+		expected := "Basic " + base64.StdEncoding.EncodeToString([]byte("myuser:mypass"))
+		require.Equal(t, expected, gotAuth, "Authorization header should be set by default (DisableAuth is false)")
+	})
+}