client: simplify test with mock-responses

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

client/secret_create_test.go

@@ -1,10 +1,7 @@
 package client
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
-	"io"
 	"net/http"
 	"testing"
 
@@ -27,16 +24,9 @@ func TestSecretCreate(t *testing.T) {
 		if err := assertRequest(req, http.MethodPost, expectedURL); err != nil {
 			return nil, err
 		}
-		b, err := json.Marshal(swarm.SecretCreateResponse{
+		return mockJSONResponse(http.StatusCreated, nil, swarm.SecretCreateResponse{
 			ID: "test_secret",
-		})
-		if err != nil {
-			return nil, err
-		}
-		return &http.Response{
-			StatusCode: http.StatusCreated,
-			Body:       io.NopCloser(bytes.NewReader(b)),
-		}, nil
+		})(req)
 	}))
 	assert.NilError(t, err)