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: nulls_test.go
    path of file: ./repos/cockroach/pkg/col/coldata
    
    the code of the file until where you have to start completion: // Copyright 2019 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.

package coldata

import (
	"fmt"
	"testing"

	"github.com/cockroachdb/cockroach/pkg/sql/types"
	"github.com/cockroachdb/cockroach/pkg/util/randutil"
	"github.com/stretchr/testify/require"
)

// noNulls is a nulls vector with no value set to null.
var noNulls Nulls

// nulls3 is a nulls ve
    
func TestNullsSet(t *testing.T) {
	args := SliceArgs{
		// Neither type nor the length here matter.
		Src: NewMemColumn(types.Bool, 0, StandardColumnFactory),
	}
	for _, withSel := range []bool{false, true} {
		t.Run(fmt.Sprintf("WithSel=%t", withSel), func(t *testing.T) {
			var srcNulls Nulls
			if withSel {
				args.Sel = make([]int, BatchSize())
				// Make a selection vector with every even index. (This turns nulls10 into
				// nulls5.)
				for i := range args.Sel {
					args.Sel[i] = i * 2
				}
				srcNulls = nulls10
			} else {
				args.Sel = nil
				srcNulls = nulls5
			}
			for _, destStartIdx := range pos {
				for _, srcStartIdx := range pos {
					for _, srcEndIdx := range pos {
						if destStartIdx <= srcStartIdx && srcStartIdx <= srcEndIdx {
							toAppend := srcEndIdx - srcStartIdx
							name := fmt.Sprintf("destStartIdx=%d,srcStartIdx=%d,toAppend=%d", destStartIdx,
								srcStartIdx, toAppend)
							t.Run(name, func(t *testing.T) {
								n := nulls3.makeCopy()
								args.Src.SetNulls(srcNulls)
								args.DestIdx = destStartIdx
								args.SrcStartIdx = srcStartIdx
								args.SrcEndIdx = srcEndIdx
								// Set some garbage values in the destination nulls that should
								// be overwritten.
								n.SetNullRange(destStartIdx, destStartIdx+toAppend)
								n.set(args)
								for i := 0; i < destStartIdx; i++ {
									require.Equal(t, nulls3.NullAt(i), n.NullAt(i))
								}
								for i := 0; i < toAppend; i++ {
									require.Equal(t, nulls5.NullAt(srcStartIdx+i), n.NullAt(destStartIdx+i))
								}
								for i := destStartIdx + toAppend; i < BatchSize(); i++ {
									require.Equal(t, nulls3.NullAt(i), n.NullAt(i))
								}
							})
						}
					}
				}
			}
		})
	}
}