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: compiler_regexp_test.go
    path of file: ./repos/ferret/pkg/compiler
    
    the code of the file until where you have to start completion: package compiler_test

import (
	"context"
	"fmt"
	"testing"

	"github.com/MontFerret/ferret/pkg/runtime/core"
	"github.com/MontFerret/ferret/pkg/runtime/values"

	. "github.com/smartystreets/goconvey/convey"

	"github.com/MontFerret/ferret/pkg/compiler"
)

func TestRegexpOperator(t *testing.T) {
	Convey("Should be possible to use positive regular expression operator", t, func() {
		out := compiler.New().
			MustCompile(`
			RETURN "foo" =~ "^f[o].$" 
		`).
			MustRun(context.Background())

		So(string(out), ShouldEqual, `true`)
	})

	Convey("Should be possible to use negative regular expression operator", t, func() {
		out := compiler.New().
			MustCompile(`
			RETURN "foo" !~ "[a-z]+bar$" 
		`).
			MustRun(context.Background())

		So(string(out), ShouldEqual, `true`)
	})

	Convey("Should be possible to use negative regular expression operator", t, func() {
		c := compiler.New()
		c.Namespace("T").RegisterFunction("REGEXP", func(_ context.Context, _ ...core.Value) (value core.Value, e error) {
			return values.NewString("[a-z
    
func TestRegexpOperator(t *testing.T) {
	Convey("Should be possible to use positive regular expression operator", t, func() {
		out := compiler.New().
			MustCompile(`
			RETURN "foo" =~ "^f[o].$" 
		`).
			MustRun(context.Background())

		So(string(out), ShouldEqual, `true`)
	})

	Convey("Should be possible to use negative regular expression operator", t, func() {
		out := compiler.New().
			MustCompile(`
			RETURN "foo" !~ "[a-z]+bar$" 
		`).
			MustRun(context.Background())

		So(string(out), ShouldEqual, `true`)
	})

	Convey("Should be possible to use negative regular expression operator", t, func() {
		c := compiler.New()
		c.Namespace("T").RegisterFunction("REGEXP", func(_ context.Context, _ ...core.Value) (value core.Value, e error) {
			return values.NewString("[a-z]+bar$"), nil
		})

		out := c.
			MustCompile(`
			RETURN "foo" !~ T::REGEXP()
		`).
			MustRun(context.Background())

		So(string(out), ShouldEqual, `true`)
	})

	Convey("Should return an error during compilation when a regexp string invalid", t, func() {
		_, err := compiler.New().
			Compile(`
			RETURN "foo" !~ "[ ]\K(?<!\d )(?=(?: ?\d){8})(?!(?: ?\d){9})\d[ \d]+\d" 
		`)

		So(err, ShouldBeError)
	})

	Convey("Should return an error during compilation when a regexp is not a string", t, func() {
		right := []string{
			"[]",
			"{}",
			"1",
			"1.1",
			"TRUE",
		}

		for _, r := range right {
			_, err := compiler.New().
				Compile(fmt.Sprintf(`
			RETURN "foo" !~ %s 
		`, r))

			So(err, ShouldBeError)
		}
	})
}