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: passthrough_test.go
    path of file: ./repos/vault/command/agentproxyshared/cache/keymanager
    
    the code of the file until where you have to start completion: // Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: BUSL-1.1

package keymanager

import (
	"bytes"
	"context"
	"testing"

	"g
    
func TestKeyManager_PassthrougKeyManager(t *testing.T) {
	tests := []struct {
		name    string
		key     []byte
		wantErr bool
	}{
		{
			"new key",
			nil,
			false,
		},
		{
			"existing valid key",
			[]byte("e679e2f3d8d0e489d408bc617c6890d6"),
			false,
		},
		{
			"invalid key length",
			[]byte("foobar"),
			true,
		},
	}

	ctx := context.Background()
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			m, err := NewPassthroughKeyManager(ctx, tc.key)
			if tc.wantErr {
				require.Error(t, err)
				return
			}
			require.NoError(t, err)

			if w := m.Wrapper(); w == nil {
				t.Fatalf("expected non-nil wrapper from the key manager")
			}

			token, err := m.RetrievalToken(ctx)
			if err != nil {
				t.Fatalf("unable to retrieve token: %s", err)
			}

			if len(tc.key) != 0 && !bytes.Equal(tc.key, token) {
				t.Fatalf("expected key bytes: %x, got: %x", tc.key, token)
			}
		})
	}
}