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: merge_test.go
    path of file: ./repos/badger
    
    the code of the file until where you have to start completion: /*
* Copyright 2019 Dgraph Labs, Inc. and Contributors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
 */

package badger

import (
	"encoding/binary"
	"os"
	"testing"
	"time"

	"github.com/stretchr/testify/require"
)

func TestGetMergeOperator(t *testing.T) {
	t.Run("Get before Add", func(t *testing.T) {
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator([]byte("merge"), add, 200*time.Millisecond)
			defer m.Stop()

			val, err := m.Get()
			require.Equal(t, ErrKeyNotFound, err)
			require.Nil(t, val)
		})
	})
	t.Run("Add and Get", func(t *testing.T) {
		key := []byte("merge")
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator(key, add, 200*time.Millisecond)
			defer m.Stop()

			require.NoError(t, m.Add(uint64ToBytes(1)))
			require.NoError(t, m.Add(uint64ToBytes(2)))
			require.NoError(t, m.Add(uint64ToBytes(3)))

			res, err := m.Get()
			require.NoError(t, err)
			require.Equal(t, uint64(6), bytesToUint64(res))
		})

	})
	t.Run("Add and Get slices", func(t *testing.T) {
		// Merge function to merge two byte slices
		add := func(originalValue, newValue []byte) []byte {
			return append(originalValue, newValue...)
		}
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator([]byte("fooprefix"), add, 2*time.Millisecond)
			defer m.Stop()

			require.NoError(t, m.Add([]byte("A")))
			require.NoError(t, m.Add([]byte("B")))
			require.NoError(t, m.Add([]byte("C")))

			value, err := m.Get()
			require.NoError(t, err)
			require.Equal(t, "ABC", string(value))
		})
	})
	t.Run("Get Before Compact", func(t *testing.T) {
		key := []byte("merge")
		runBadgerTest(t, nil, func(t 
    
func TestGetMergeOperator(t *testing.T) {
	t.Run("Get before Add", func(t *testing.T) {
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator([]byte("merge"), add, 200*time.Millisecond)
			defer m.Stop()

			val, err := m.Get()
			require.Equal(t, ErrKeyNotFound, err)
			require.Nil(t, val)
		})
	})
	t.Run("Add and Get", func(t *testing.T) {
		key := []byte("merge")
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator(key, add, 200*time.Millisecond)
			defer m.Stop()

			require.NoError(t, m.Add(uint64ToBytes(1)))
			require.NoError(t, m.Add(uint64ToBytes(2)))
			require.NoError(t, m.Add(uint64ToBytes(3)))

			res, err := m.Get()
			require.NoError(t, err)
			require.Equal(t, uint64(6), bytesToUint64(res))
		})

	})
	t.Run("Add and Get slices", func(t *testing.T) {
		// Merge function to merge two byte slices
		add := func(originalValue, newValue []byte) []byte {
			return append(originalValue, newValue...)
		}
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator([]byte("fooprefix"), add, 2*time.Millisecond)
			defer m.Stop()

			require.NoError(t, m.Add([]byte("A")))
			require.NoError(t, m.Add([]byte("B")))
			require.NoError(t, m.Add([]byte("C")))

			value, err := m.Get()
			require.NoError(t, err)
			require.Equal(t, "ABC", string(value))
		})
	})
	t.Run("Get Before Compact", func(t *testing.T) {
		key := []byte("merge")
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator(key, add, 500*time.Millisecond)
			defer m.Stop()

			require.NoError(t, m.Add(uint64ToBytes(1)))
			require.NoError(t, m.Add(uint64ToBytes(2)))
			require.NoError(t, m.Add(uint64ToBytes(3)))

			res, err := m.Get()
			require.NoError(t, err)
			require.Equal(t, uint64(6), bytesToUint64(res))
		})
	})

	t.Run("Get after Delete", func(t *testing.T) {
		key := []byte("merge")
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator(key, add, 200*time.Millisecond)

			require.NoError(t, m.Add(uint64ToBytes(1)))
			require.NoError(t, m.Add(uint64ToBytes(2)))
			require.NoError(t, m.Add(uint64ToBytes(3)))

			m.Stop()
			res, err := m.Get()
			require.NoError(t, err)
			require.Equal(t, uint64(6), bytesToUint64(res))

			require.NoError(t, db.Update(func(txn *Txn) error {
				return txn.Delete(key)
			}))

			m = db.GetMergeOperator(key, add, 200*time.Millisecond)
			require.NoError(t, m.Add(uint64ToBytes(1)))
			m.Stop()

			res, err = m.Get()
			require.NoError(t, err)
			require.Equal(t, uint64(1), bytesToUint64(res))
		})
	})

	t.Run("Get after Stop", func(t *testing.T) {
		key := []byte("merge")
		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
			m := db.GetMergeOperator(key, add, 1*time.Second)

			require.NoError(t, m.Add(uint64ToBytes(1)))
			require.NoError(t, m.Add(uint64ToBytes(2)))
			require.NoError(t, m.Add(uint64ToBytes(3)))

			m.Stop()
			res, err := m.Get()
			require.NoError(t, err)
			require.Equal(t, uint64(6), bytesToUint64(res))
		})
	})
	t.Run("Old keys should be removed after compaction", func(t *testing.T) {
		dir, err := os.MkdirTemp("", "badger-test")
		require.NoError(t, err)
		defer removeDir(dir)

		// This test relies on CompactL0OnClose
		opts := getTestOptions(dir).WithCompactL0OnClose(true)
		db, err := Open(opts)
		require.NoError(t, err)
		mergeKey := []byte("foo")
		m := db.GetMergeOperator(mergeKey, add, 2*time.Millisecond)

		count := 5000 // This will cause compaction from L0->L1
		for i := 0; i < count; i++ {
			require.NoError(t, m.Add(uint64ToBytes(1)))
		}
		value, err := m.Get()
		require.Nil(t, err)
		require.Equal(t, uint64(count), bytesToUint64(value))
		m.Stop()

		// Force compaction by closing DB. The compaction should discard all the old merged values
		require.Nil(t, db.Close())
		db, err = Open(opts)
		require.NoError(t, err)
		defer db.Close()

		keyCount := 0
		txn := db.NewTransaction(false)
		defer txn.Discard()
		iopt := DefaultIteratorOptions
		iopt.AllVersions = true
		it := txn.NewKeyIterator(mergeKey, iopt)
		defer it.Close()
		for it.Rewind(); it.Valid(); it.Next() {
			keyCount++
		}
		// We should have only one key in badger. All the other keys should've been removed by
		// compaction
		require.Equal(t, 1, keyCount)
	})

}