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: reader_test.go
    path of file: ./repos/pyroscope/pkg/objstore
    
    the code of the file until where you have to start completion: package objstore_test

import (
	"context"
	"os"
	"path/filepath"
	"testing"

	"github.com/stretchr/testify/require"

	"github.com/grafana/pyroscope/pkg/objstore/client"
	"github.com/grafana/pyroscope/pkg/objstore/providers/filesystem"
)

func Test_FileSystem(t *testing.T) {
	testDir := t.TempDir()
	b, err := client.NewBucket(context.Background(), client.Config{
		StorageBackendConfig: client.StorageBackendConfig{
			Backend: client.Filesystem,
			Filesystem: filesystem.Config{
				Directory: testDir,
			},
		},
		StoragePrefix: "testdata/",
	}, "foo")
	require.NoError(t, err)

	// make the file locally
	dir := filepath.Join(testDir, "testdata")
	require.NoError(t, os.M
    
func Test_FileSystem(t *testing.T) {
	testDir := t.TempDir()
	b, err := client.NewBucket(context.Background(), client.Config{
		StorageBackendConfig: client.StorageBackendConfig{
			Backend: client.Filesystem,
			Filesystem: filesystem.Config{
				Directory: testDir,
			},
		},
		StoragePrefix: "testdata/",
	}, "foo")
	require.NoError(t, err)

	// make the file locally
	dir := filepath.Join(testDir, "testdata")
	require.NoError(t, os.MkdirAll(dir, 0o755))
	require.NoError(t, os.WriteFile(dir+"/foo.parquet", []byte(`12345`), 0o644))

	ra, err := b.ReaderAt(context.Background(), "foo.parquet")
	require.NoError(t, err)
	defer func() {
		require.NoError(t, ra.Close())
	}()
	require.NotNil(t, ra)
	require.IsType(t, &filesystem.FileReaderAt{}, ra)

	buf := make([]byte, 2)
	read, err := ra.ReadAt(buf, 3)
	require.NoError(t, err)
	require.Equal(t, 2, read)
	require.Equal(t, []byte("45"), buf)
}