testutils: make the package public (#4290)

This package can be useful outside of quic-go. We're not making any API
guarantees at this point.

connection_test.go

@@ -21,10 +21,10 @@ import (
  mocklogging "github.com/quic-go/quic-go/internal/mocks/logging"
  "github.com/quic-go/quic-go/internal/protocol"
  "github.com/quic-go/quic-go/internal/qerr"
- "github.com/quic-go/quic-go/internal/testutils"
  "github.com/quic-go/quic-go/internal/utils"
  "github.com/quic-go/quic-go/internal/wire"
  "github.com/quic-go/quic-go/logging"
+ "github.com/quic-go/quic-go/testutils"
 
  . "github.com/onsi/ginkgo/v2"
  . "github.com/onsi/gomega"

integrationtests/self/mitm_test.go

@@ -15,8 +15,8 @@ import (
  "github.com/quic-go/quic-go"
  quicproxy "github.com/quic-go/quic-go/integrationtests/tools/proxy"
  "github.com/quic-go/quic-go/internal/protocol"
- "github.com/quic-go/quic-go/internal/testutils"
  "github.com/quic-go/quic-go/internal/wire"
+ "github.com/quic-go/quic-go/testutils"
 
  . "github.com/onsi/ginkgo/v2"
  . "github.com/onsi/gomega"

internal/testutils/testutils.go → testutils/testutils.go

@@ -1,3 +1,6 @@
+// Package testutils contains utilities for simulating packet injection and man-in-the-middle (MITM) attacker tests.
+// It is not supposed to be used for non-testing purposes.
+// The API is not guaranteed to be stable.
 package testutils
 
 import (
@@ -8,9 +11,6 @@ import (
  "github.com/quic-go/quic-go/internal/wire"
 )
 
-// Utilities for simulating packet injection and man-in-the-middle (MITM) attacker tests.
-// Do not use for non-testing purposes.
-
 // writePacket returns a new raw packet with the specified header and payload
 func writePacket(hdr *wire.ExtendedHeader, data []byte) []byte {
  b, err := hdr.Append(nil, hdr.Version)