Blackhole outbound: Add customizable response data support (#6713)

https://github.com/XTLS/Xray-core/pull/6711#issuecomment-5508683394

---------

Co-authored-by: Raaad1on <djilyawhite@gmail.com>

proxy/blackhole/config_test.go

@@ -1,26 +1,19 @@
 package blackhole_test
 
 import (
-	"bufio"
-	"net/http"
+	"context"
 	"testing"
 
 	"github.com/xtls/xray-core/common"
-	"github.com/xtls/xray-core/common/buf"
-	. "github.com/xtls/xray-core/proxy/blackhole"
+	"github.com/xtls/xray-core/proxy/blackhole"
 )
 
 func TestHTTPResponse(t *testing.T) {
-	buffer := buf.New()
-
-	httpResponse := new(HTTPResponse)
-	httpResponse.WriteTo(buf.NewWriter(buffer))
-
-	reader := bufio.NewReader(buffer)
-	response, err := http.ReadResponse(reader, nil)
+	handler, err := blackhole.New(context.Background(), &blackhole.Config{
+		Response: &blackhole.Response{Type: "http"},
+	})
 	common.Must(err)
-
-	if response.StatusCode != 403 {
-		t.Error("expected status code 403, but got ", response.StatusCode)
+	if handler == nil {
+		t.Error("expected HTTP response handler")
 	}
 }