@@ -411,9 +411,7 @@ func (s *DockerCLICpSuite) TestCpToErrReadOnlyRootfs(c *testing.T) {

 	dstPath := containerCpPath(containerID, "/root/shouldNotExist")

 	err := runDockerCp(c, srcPath, dstPath)

-	assert.ErrorContains(c, err, "")

-

-	assert.Assert(c, isCpCannotCopyReadOnly(err), "expected ErrContainerRootfsReadonly error, but got %T: %s", err, err)

+	assert.ErrorContains(c, err, "marked read-only")

 	assert.NilError(c, containerStartOutputEquals(c, containerID, ""), "dstPath should not have existed")

 }

@@ -436,8 +434,7 @@ func (s *DockerCLICpSuite) TestCpToErrReadOnlyVolume(c *testing.T) {

 	dstPath := containerCpPath(containerID, "/vol_ro/shouldNotExist")

 	err := runDockerCp(c, srcPath, dstPath)

-	assert.ErrorContains(c, err, "")

+	assert.ErrorContains(c, err, "marked read-only")

-	assert.Assert(c, isCpCannotCopyReadOnly(err), "expected ErrVolumeReadonly error, but got %T: %s", err, err)

 	assert.NilError(c, containerStartOutputEquals(c, containerID, ""), "dstPath should not have existed")

 }

@@ -232,10 +232,6 @@ func isCpCannotCopyDir(err error) bool {

 	return strings.Contains(err.Error(), archive.ErrCannotCopyDir.Error())

 }

-func isCpCannotCopyReadOnly(err error) bool {

-	return strings.Contains(err.Error(), "marked read-only")

-}

-

 func fileContentEquals(c *testing.T, filename, contents string) error {

 	c.Helper()