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: swarm_get_unlock_key_test.go
    path of file: ./repos/moby/client
    
    the code of the file until where you have to start completion: package client // import "github.com/docker/docker/client"

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"testing"

	"github.com/docker/docker/api/types"
	"github.com/docker/docker/errdefs"
	"gotest.tools/v3/assert"
	is "gotest.tools/v3/assert/cmp"
)

func TestSwarmGetUnlockKeyError(t *testing.T) {
	client := &Client{
		client: newMockClient(errorMock(http.StatusInternalServerError, "Server error")),
	}

	_, err := client.SwarmGetUnlockKey(contex
    
func TestSwarmGetUnlockKey(t *testing.T) {
	expectedURL := "/swarm/unlockkey"
	unlockKey := "SWMKEY-1-y6guTZNTwpQeTL5RhUfOsdBdXoQjiB2GADHSRJvbXeE"

	client := &Client{
		client: newMockClient(func(req *http.Request) (*http.Response, error) {
			if !strings.HasPrefix(req.URL.Path, expectedURL) {
				return nil, fmt.Errorf("Expected URL '%s', got '%s'", expectedURL, req.URL)
			}
			if req.Method != http.MethodGet {
				return nil, fmt.Errorf("expected GET method, got %s", req.Method)
			}

			key := types.SwarmUnlockKeyResponse{
				UnlockKey: unlockKey,
			}

			b, err := json.Marshal(key)
			if err != nil {
				return nil, err
			}

			return &http.Response{
				StatusCode: http.StatusOK,
				Body:       io.NopCloser(bytes.NewReader(b)),
			}, nil
		}),
	}

	resp, err := client.SwarmGetUnlockKey(context.Background())
	assert.NilError(t, err)
	assert.Check(t, is.Equal(unlockKey, resp.UnlockKey))
}