You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: private_test.go
    path of file: ./repos/jackal/pkg/storage/cached
    
    the code of the file until where you have to start completion: // Copyright 2022 The jackal Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permiss
    
func TestCachedPrivateRep_UpsertPrivate(t *testing.T) {
	// given
	var cacheNS, cacheKey string

	cacheMock := &cacheMock{}
	cacheMock.DelFunc = func(ctx context.Context, ns string, keys ...string) error {
		cacheNS = ns
		cacheKey = keys[0]
		return nil
	}

	repMock := &repositoryMock{}
	repMock.UpsertPrivateFunc = func(ctx context.Context, private stravaganza.Element, namespace string, username string) error {
		return nil
	}

	// when
	rep := cachedPrivateRep{
		c:   cacheMock,
		rep: repMock,
	}
	prv := stravaganza.NewBuilder("prv").Build()

	err := rep.UpsertPrivate(context.Background(), prv, "n0", "u1")

	// then
	require.NoError(t, err)
	require.Equal(t, privateNS("u1"), cacheNS)
	require.Equal(t, "n0", cacheKey)
	require.Len(t, repMock.UpsertPrivateCalls(), 1)
}