How to unit test code consuming gcloud storage? - go

Question

I want to write unit test for the below code
package main
import (
"context"
"google.golang.org/api/option"
"cloud.google.com/go/storage"
)
var (
NewClient = storage.NewClient
)
func InitializeClient(ctx context.Context) (*storage.Client, error) {
credFilePath := "Storage credentials path."
// Creates a client.
client, err := NewClient(ctx, option.WithCredentialsFile(credFilePath))
if err != nil {
return nil, err
}
return client, nil
}
func createStorageBucket(ctx context.Context, client *storage.Client, bucketName string) (*storage.BucketHandle, error) {
// Sets your Google Cloud Platform project ID.
projectID := "Some project id"
// Creates a Bucket instance.
bucket := client.Bucket(bucketName)
// Creates the new bucket.
ctx, cancel := context.WithTimeout(ctx, time.Second*10)
defer cancel()
if err := bucket.Create(ctx, projectID, nil); err != nil {
return nil, err
}
return bucket, nil
}
func bucketExists(ctx context.Context, client *storage.Client, bucketName string) error {
bucket := client.Bucket(bucketName)
if _, err := bucket.Attrs(ctx); err != nil {
//try creating the bucket
if _, err := createStorageBucket(ctx, client, bucketName); err != nil {
return err
}
}
return nil
}
func main() {
ctx = context.Background()
client, err := InitializeClient(ctx)
bucketName := "Some bucket name"
err = bucketExists(ctx, client, bucketName)
}
bucket.Create() and bucket.Attrs() are http calls, also Bucket(), Object() and NewReader() returning structs(So in my sense there is no meaning of implement interface for this use case)
Note: storage.NewClient() is also http call but i am avoiding external call using monkey pathching approch in my test by providing custom implementaion.
var (
NewClient = storage.NewClient
)

Answer 1

The code is so thin that is is hard to figure how to test that.
I guess Flimzy grasped that reading at the title.
There is a fundamental misunderstanding because of/in the title How to write unit test for gcloud storage?.
Well we should not. They did it. A better title would be How to unit test code consuming gcloud storage? I am not trying to be picky here, but explains what i understood trying to solve that question.
So anyways, this whole thing lead me to write less thin code, so that i can test that the code i write, the lines driving the storage, did what we expect it does.
This whole thing is so convoluted and out of tin air that I dont think it will answer your question.
but anyways, if that helps thinking about this difficulty that is already a win.
package main
import (
"context"
"flag"
"fmt"
"testing"
"time"
"cloud.google.com/go/storage"
"google.golang.org/api/option"
)
type client struct {
c *storage.Client
projectID string
}
func New() client {
return client{}
}
func (c *client) Initialize(ctx context.Context, projectID string) error {
credFilePath := "Storage credentials path."
x, err := NewClient(ctx, option.WithCredentialsFile(credFilePath))
if err == nil {
c.c = x
c.projectID = projectID
}
return err
}
func (c client) BucketExists(ctx context.Context, bucketName string) bool {
if c.c == nil {
return nil, fmt.Errorf("not initialized")
}
bucket := c.c.Bucket(bucketName)
err := bucket.Attrs(ctx)
return err == nil
}
func (c client) CreateBucket(ctx context.Context, bucketName string) (*storage.BucketHandle, error) {
if c.c == nil {
return nil, fmt.Errorf("not initialized")
}
bucket := c.c.Bucket(bucketName)
err := bucket.Create(ctx, c.projectID, nil)
if err != nil {
return nil, err
}
return bucket, err
}
func (c client) CreateBucketIfNone(ctx context.Context, bucketName string) (*storage.BucketHandle, error) {
if !c.BucketExists(bucketName) {
return c.CreateBucket(ctx, c.projectID, bucketName)
}
return c.c.Bucket(bucketName), nil
}
type clientStorageProvider interface { // give it a better name..
Initialize(ctx context.Context, projectID string) (err error)
CreateBucketIfNone(ctx context.Context, bucketName string) (*storage.BucketHandle, error)
CreateBucket(ctx context.Context, bucketName string) (*storage.BucketHandle, error)
BucketExists(ctx context.Context, bucketName string) bool
}
func main() {
flag.Parse()
cmd := flag.Arg(0)
projectID := flag.Arg(1)
bucketName := flag.Arg(2)
ctx, cancel := context.WithTimeout(context.Background(), time.Second*10)
defer cancel()
client := New()
if cmd == "create" {
createBucket(ctx, client, projectID, bucketName)
} else {
// ... more
}
}
// this is the part we are going to test.
func createBucket(ctx context.Context, client clientStorageProvider, projectID, bucketName string) error {
err := client.Initialize(ctx, projectID)
if err != nil {
return err
}
return client.CreateBucketIfNone(bucketName)
// maybe we want to apply retry strategy here,
// and test that the retry was done;
}
type clientFaker struct {
initErr error
createErr error
createIfNoneErr error
bucketExistsErr error
}
func (c clientFaker) Initialize(ctx context.Context, projectID string) (err error) {
return c.initErr
}
func (c clientFaker) CreateBucketIfNone(ctx context.Context, bucketName string) (*storage.BucketHandle, error) {
return nil, c.createIfNoneErr
}
func (c clientFaker) CreateBucket(ctx context.Context, bucketName string) (*storage.BucketHandle, error) {
return nil, c.createErr
}
func (c clientFaker) BucketExists(ctx context.Context, bucketName string) bool {
return nil, c.bucketExistsErr
}
func TestCreateBucketWithFailedInit(t *testing.T) {
c := clientFaker{
initErr: fmt.Errorf("failed init"),
}
ctx := context.Background()
err := createBucket(ctx, c, "", "")
if err == nil {
t.Fatalf("should have failed to initialize the bucket")
}
}
// etc...
note that i am not happy having *storage.BucketHandle as a return parameter, too specific, but i had no use of it (i put it here because it was there, otherwise hanging), so it was hard to design something around that.
note², it might happen my code is not fully compilable. I am having a dependency problem that i don t want to fix now and it prevent me from seeing all errors (it stops too early in the process)