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: cache_test.go
    path of file: ./repos/evans/cache
    
    the code of the file until where you have to start completion: package cache

import (
	"io"
	"os"
	"testing"
)

func TestMain(m *testing.M) {
	// Create a temp dir to reserve dir name. But remove it, and create again later.
	dir := os.TempDir()

	oldCacheDir := os.Getenv("XDG_CACHE_HOME")
	os.Setenv("XDG_CACHE_HOME", dir)

	code := m.Run()

	os.Setenv("XDG_CACHE_HOME", oldCacheDir)
	os.Exit(code)
}

func TestCache(t *testing.T) {
	t.Run("Get creates a new one", func(t *tes
    
func TestCache(t *testing.T) {
	t.Run("Get creates a new one", func(t *testing.T) {
		_, err := Get()
		if err != nil {
			t.Fatalf("Get must not return an error, but got '%s'", err)
		}
	})

	t.Run("the file is empty", func(t *testing.T) {
		oldDecodeTOML := decodeTOML
		defer func() {
			decodeTOML = oldDecodeTOML
		}()
		// Do nothing.
		decodeTOML = func(r io.Reader, v interface{}) error {
			return nil
		}
		_, err := Get()
		if err != nil {
			t.Fatalf("Get must not return an error, but got '%s'", err)
		}
	})

	t.Run("Save", func(t *testing.T) {
		c, err := Get()
		if err != nil {
			t.Fatalf("Get must not return an error, but got '%s'", err)
		}
		c.Version = "5.0.0"
		if err := c.Save(); err != nil {
			t.Fatalf("must not return an error, but got '%s'", err)
		}
	})
}