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: folder_getsubfolder_test.go
    path of file: ./repos/wal-g/internal/multistorage
    
    the code of the file until where you have to start completion: package multistorage

import (
	"testing"

	"github.com/stretchr/testify/assert"
	"github.com/wal-g/wal-g/internal/multistorage/policies"
)

// TODO: Unit tests: check Folder.statsCollector.ReportOperationResult calls
func TestGetSubFolder(t *testing.T) {
	t.Run("change path in all storages regardless of policies", func(t *testing.T) {
		folder := newTestFolder(t, "s1", "s2")
		folder.policies = policies.TakeFirstStorage

		subf := folder.GetSubFolder("a")
		aSubFolder, ok := subf.(Folder)
		assert.True(t, ok)

    
func TestGetSubFolder(t *testing.T) {
	t.Run("change path in all storages regardless of policies", func(t *testing.T) {
		folder := newTestFolder(t, "s1", "s2")
		folder.policies = policies.TakeFirstStorage

		subf := folder.GetSubFolder("a")
		aSubFolder, ok := subf.(Folder)
		assert.True(t, ok)
		assert.Equal(t, "a/", aSubFolder.GetPath())
		assert.Len(t, aSubFolder.usedFolders, 2)
		assert.Equal(t, "s1/a/", aSubFolder.usedFolders[0].GetPath())
		assert.Equal(t, "s2/a/", aSubFolder.usedFolders[1].GetPath())

		subf = aSubFolder.GetSubFolder("b")
		bSubFolder, ok := subf.(Folder)
		assert.True(t, ok)
		assert.Equal(t, "a/b/", bSubFolder.GetPath())
		assert.Len(t, bSubFolder.usedFolders, 2)
		assert.Equal(t, "s1/a/b/", bSubFolder.usedFolders[0].GetPath())
		assert.Equal(t, "s2/a/b/", bSubFolder.usedFolders[1].GetPath())
	})

	t.Run("copies stats collector storages and policies to subfolders", func(t *testing.T) {
		folder := newTestFolder(t, "s1", "s2")
		folder.policies = policies.UniteAllStorages

		subf := folder.GetSubFolder("a")
		aSubFolder, ok := subf.(Folder)
		assert.True(t, ok)
		assert.Equal(t, policies.UniteAllStorages, aSubFolder.policies)
		assert.Len(t, aSubFolder.usedFolders, 2)
		assert.Equal(t, "s1", aSubFolder.usedFolders[0].StorageName)
		assert.Equal(t, "s2", aSubFolder.usedFolders[1].StorageName)
		assert.Equal(t, folder.statsCollector, aSubFolder.statsCollector)
	})
}