github.com/cenkalti/backoff/v5 v5.0.3: NewConstantBackOff

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify github.com/cenkalti/backoff/v5.NewConstantBackOff in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3
Demonstrate these symbols/APIs:
  - github.com/cenkalti/backoff/v5.NewConstantBackOff

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:f6b3a5e1a4c147fb2c52f3cbea7d3b2b163311e6f0d1ceb58cb324b938aa66a5","contract":["ConstantBackOff implements the BackOff interface","NewConstantBackOff creates a ConstantBackOff with the specified interval","ConstantBackOff.NextBackOff repeatedly returns the configured constant interval","ConstantBackOff.Reset preserves the configured interval","NewConstantBackOff configures Retry to repeat failed operations with constant backoff until success"],"goal":"verify github.com/cenkalti/backoff/v5.NewConstantBackOff in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3","kind":"HOW","packages":["pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"],"schemaVersion":1,"symbols":["github.com/cenkalti/backoff/v5.NewConstantBackOff"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"],"schemaVersion":1,"subject":"pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3","symbols":["github.com/cenkalti/backoff/v5.NewConstantBackOff"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require github.com/cenkalti/backoff/v5 v5.0.3

github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1xcsSM=
github.com/cenkalti/backoff/v5 v5.0.3/go.mod h1:rkhZdG3JZukswDf7f0cwqPNk4K0sa+F97BxZthm/crw=

package main

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/cenkalti/backoff/v5"
)

func main() {
	attempts := 0
	operation := func() (string, error) {
		attempts++
		if attempts < 3 {
			return "", errors.New("temporary network glitch")
		}
		return "connected successfully", nil
	}

	b := backoff.NewConstantBackOff(10 * time.Millisecond)
	result, err := backoff.Retry(
		context.Background(),
		operation,
		backoff.WithBackOff(b),
		backoff.WithMaxTries(5),
	)
	if err != nil {
		fmt.Printf("retry failed: %v\n", err)
		return
	}

	fmt.Printf("operation succeeded after %d attempts: %s\n", attempts, result)
}

{
  "schemaVersion": 1,
  "goal": "verify github.com/cenkalti/backoff/v5.NewConstantBackOff in pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3",
  "kind": "HOW",
  "packages": [
    "pkg:golang/github.com/cenkalti/backoff/v5@v5.0.3"
  ],
  "symbols": [
    "github.com/cenkalti/backoff/v5.NewConstantBackOff"
  ]
}

package main

import (
	"context"
	"errors"
	"fmt"
	"os"
	"time"

	"github.com/cenkalti/backoff/v5"
)

func main() {
	// 1. ConstantBackOff implements the BackOff interface
	var _ backoff.BackOff = (*backoff.ConstantBackOff)(nil)

	// 2. NewConstantBackOff creates a ConstantBackOff with the specified interval
	interval := 150 * time.Millisecond
	b := backoff.NewConstantBackOff(interval)
	if b == nil {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: NewConstantBackOff returned nil\n")
		os.Exit(1)
	}
	if b.Interval != interval {
		fmt.Fprintf(os.Stderr, "assertion 2 failed: expected Interval %v, got %v\n", interval, b.Interval)
		os.Exit(1)
	}

	// 3. ConstantBackOff.NextBackOff repeatedly returns the configured constant interval
	for i := 1; i <= 5; i++ {
		got := b.NextBackOff()
		if got != interval {
			fmt.Fprintf(os.Stderr, "assertion 3 failed at call %d: expected %v, got %v\n", i, interval, got)
			os.Exit(1)
		}
	}

	// 4. ConstantBackOff.Reset preserves the configured interval
	b.Reset()
	if b.Interval != interval {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: expected Interval %v after Reset, got %v\n", interval, b.Interval)
		os.Exit(1)
	}
	if got := b.NextBackOff(); got != interval {
		fmt.Fprintf(os.Stderr, "assertion 4 failed: expected %v after Reset, got %v\n", interval, got)
		os.Exit(1)
	}

	// 5. NewConstantBackOff configures Retry to repeat failed operations with constant backoff until success
	{
		attempts := 0
		op := func() (string, error) {
			attempts++
			if attempts < 3 {
				return "", errors.New("temporary error")
			}
			return "success", nil
		}

		res, err := backoff.Retry(
			context.Background(),
			op,
			backoff.WithBackOff(backoff.NewConstantBackOff(0)),
			backoff.WithMaxTries(5),
		)
		if err != nil {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: unexpected error: %v\n", err)
			os.Exit(1)
		}
		if res != "success" || attempts != 3 {
			fmt.Fprintf(os.Stderr, "assertion 5 failed: expected res='success' and attempts=3, got res=%q, attempts=%d\n", res, attempts)
			os.Exit(1)
		}
	}

	fmt.Println("All contract assertions passed successfully.")
}