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: oviewer_test.go
    path of file: ./repos/ov/oviewer
    
    the code of the file until where you have to start completion: package oviewer

import (
	"bytes"
	"io"
	"path/filepath"
	"reflect"
	"testing"

	"github.com/gdamore/tcell/v2"
	"github.com/spf13/viper"
)

const cwd = ".."

var testdata = filepath.Join(cwd, "testdata")

func fakeScreen() (tcell.Screen, error) {
	return tcell.NewSimulationScreen(""), nil
}

func TestNewOviewer(t *testing.T) {
	tcellNewScreen = fakeScreen
	defer func() {
		tcellNewScreen = tcell.NewScreen
	}()
	type args struct {
		docs []*Document
	}
	tests := []struct {
		name    string
		args    args
		want    *
    
func TestOpen(t *testing.T) {
	tcellNewScreen = fakeScreen
	defer func() {
		tcellNewScreen = tcell.NewScreen
	}()
	type args struct {
		fileNames []string
	}
	tests := []struct {
		name    string
		args    args
		wantErr bool
	}{
		{
			name: "test1",
			args: args{
				fileNames: []string{filepath.Join(testdata, "/test.txt")},
			},
			wantErr: false,
		},
		{
			name: "test2",
			args: args{
				fileNames: []string{
					filepath.Join(testdata, "test.txt"),
					filepath.Join(testdata, "test2.txt"),
				},
			},
			wantErr: false,
		},
		{
			name: "testErr",
			args: args{
				fileNames: []string{filepath.Join(testdata, "err.txt")},
			},
			wantErr: true,
		},
		{
			name: "testDir",
			args: args{
				fileNames: []string{testdata},
			},
			wantErr: true,
		},
	}
	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			root, err := Open(tt.args.fileNames...)
			if (err != nil) != tt.wantErr {
				t.Errorf("Open() error = %v, wantErr %v", err, tt.wantErr)
				return
			}
			root.Quit()
		})
	}
}