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: fixtures.go
    path of file: ./repos/cockroach/pkg/cmd/roachtest/tests
    
    the code of the file until where you have to start completion: // Copyright 2018 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 tests

import (
	"context"
	"os"
	"runtime"
	"time"

	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/cluster"
	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/registry"
	"github.com/cockroachdb/cockroach/pkg/cmd/roachtest/test"
)

func registerFixtures(r registry.Registry) {
	// Run this test to create a new fixture for the version upgrade test. This
	// is necessary after every release. For example, the day `master` becomes
	// the 20.2 release, this test will fail because it is missing a fixture for
	// 20.1; run the test (on 20.1). Check it in (instructions will be logged
	// below) and off we go.
	//
	// The version to create/update the fixture for must be released
	// (i.e.  can download it from the homepage). For example, to make a
	// "v20.2" fixture, you will need a binary that has "v20.2" in the
	// output of `./cockroach version`, and this process will end up
	// creating fixtures that have "v20.2" in them. This would be part
	// of tagging the master branch as v21.1 in the process of going
	// through the major release for v20.2. The version is 
    
func registerFixtures(r registry.Registry) {
	// Run this test to create a new fixture for the version upgrade test. This
	// is necessary after every release. For example, the day `master` becomes
	// the 20.2 release, this test will fail because it is missing a fixture for
	// 20.1; run the test (on 20.1). Check it in (instructions will be logged
	// below) and off we go.
	//
	// The version to create/update the fixture for must be released
	// (i.e.  can download it from the homepage). For example, to make a
	// "v20.2" fixture, you will need a binary that has "v20.2" in the
	// output of `./cockroach version`, and this process will end up
	// creating fixtures that have "v20.2" in them. This would be part
	// of tagging the master branch as v21.1 in the process of going
	// through the major release for v20.2. The version is passed in as
	// FIXTURE_VERSION environment variable. The contents of this
	// environment variable must match a released cockroach binary.
	//
	// Please note that you do *NOT* need to update the fixtures in a patch
	// release. This only happens as part of preparing the master branch for the
	// next release. The release team runbooks, at time of writing, reflect
	// this.
	//
	// Example invocation:
	//   FIXTURE_VERSION=v20.2.0-beta.1 roachtest --local run generate-fixtures \
	//     --debug --cockroach ./cockroach --suite fixtures
	runFixtures := func(
		ctx context.Context,
		t test.Test,
		c cluster.Cluster,
	) {
		if c.IsLocal() && runtime.GOARCH == "arm64" {
			t.Skip("Skip under ARM64. See https://github.com/cockroachdb/cockroach/issues/89268")
		}
		fixtureVersion := os.Getenv("FIXTURE_VERSION")
		if fixtureVersion == "" {
			t.Fatal("FIXTURE_VERSION must be set")
		}
		makeVersionFixtureAndFatal(ctx, t, c, fixtureVersion)
	}
	spec := registry.TestSpec{
		Name:             "generate-fixtures",
		Timeout:          30 * time.Minute,
		CompatibleClouds: registry.AllExceptAWS,
		Suites:           registry.Suites(registry.Fixtures),
		Owner:            registry.OwnerDevInf,
		Cluster:          r.MakeClusterSpec(4),
		Run:              runFixtures,
	}
	r.Add(spec)
}