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: miner_api_test.go
    path of file: ./repos/lotus/markets/dagstore
    
    the code of the file until where you have to start completion: // stm: #unit
package dagstore

import (
	"bytes"
	"context"
	"io"
	"sync"
	"sync/atomic"
	"testing"
	"time"

	"github.com/ipfs/go-cid"
	ds "github.com/ipfs/go-datastore"
	ds_sync "github.com/ipfs/go-datastore/sync"
	"github.com/stretchr/testify/require"
	"golang.org/x/sync/errgroup"

	"github.com/filecoin-project/dagstore/mount"
	"github.com/filecoin-project/go-address"
	"github.com/filecoin-project/go-fil-markets/piecestore"
	piecestoreimpl "github.com/filecoin-project/go-fil-markets/piecestore/impl"
	"github.com/filecoin-project/go-fil-markets/retrievalmarket"
	"github.com/filecoin-project/go-fil-markets/shared"
	"github.com/filecoin-project/go-state-types/abi"
	paychtypes "github.com/fileco
    
func TestThrottle(t *testing.T) {
	ctx := context.Background()
	cid1, err := cid.Parse("bafkqaaa")
	require.NoError(t, err)

	ps := getPieceStore(t)
	rpn := &mockRPN{
		sectors: map[abi.SectorNumber]string{
			unsealedSectorID: "foo",
		},
	}
	api := NewMinerAPI(ps, rpn, 3, 5)
	require.NoError(t, api.Start(ctx))

	// Add a deal with data Length 10
	dealInfo := piecestore.DealInfo{
		SectorID: unsealedSectorID,
		Length:   10,
	}
	err = ps.AddDealForPiece(cid1, cid.Undef, dealInfo)
	require.NoError(t, err)

	// hold the lock to block.
	rpn.lk.Lock()

	// fetch the piece concurrently.
	errgrp, ctx := errgroup.WithContext(context.Background())
	for i := 0; i < 10; i++ {
		errgrp.Go(func() error {
			//stm: @MARKET_DAGSTORE_FETCH_UNSEALED_PIECE_001
			r, err := api.FetchUnsealedPiece(ctx, cid1)
			if err == nil {
				_ = r.Close()
			}
			return err
		})
	}

	time.Sleep(500 * time.Millisecond)
	require.EqualValues(t, 3, atomic.LoadInt32(&rpn.calls)) // throttled

	// allow to proceed.
	rpn.lk.Unlock()

	// allow all to finish.
	err = errgrp.Wait()
	require.NoError(t, err)

	require.EqualValues(t, 10, atomic.LoadInt32(&rpn.calls)) // throttled

}