go.step.sm/crypto v0.89.0: randutil.Hex

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 go.step.sm/crypto/randutil.Hex in pkg:golang/go.step.sm/crypto@v0.89.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/go.step.sm/crypto@v0.89.0
Demonstrate these symbols/APIs:
  - go.step.sm/crypto/randutil.Hex

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:fc3abbcaf9f1e91c53bf5413e10fa07c95cb2254a511f401741beb85f5446381","contract":["Hex returns lowercase hexadecimal string of the requested length","Hex with zero length returns an empty string without error","Hex output contains only characters in range 0-9 and a-f","Hex generates distinct random values across consecutive calls"],"goal":"verify go.step.sm/crypto/randutil.Hex in pkg:golang/go.step.sm/crypto@v0.89.0","kind":"HOW","packages":["pkg:golang/go.step.sm/crypto@v0.89.0"],"schemaVersion":1,"symbols":["go.step.sm/crypto/randutil.Hex"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/go.step.sm/crypto@v0.89.0"],"schemaVersion":1,"subject":"pkg:golang/go.step.sm/crypto@v0.89.0","symbols":["go.step.sm/crypto/randutil.Hex"],"verifierAdapter":"golang@1"}

module sample

go 1.26.6

require go.step.sm/crypto v0.89.0

require github.com/pkg/errors v0.9.1 // indirect

github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=
github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 h1:Jamvg5psRIccs7FGNTlIRMkT8wgtp5eCXdBlqhYGL6U=
github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
go.step.sm/crypto v0.89.0 h1:NPxryE+cZ4XDwXOQY2U6Gu+mOzOihuRLPIsX7WtPzZM=
go.step.sm/crypto v0.89.0/go.mod h1:IEgE6DndnYojbDyHU7eYXpwWzpu4ftkouw7nyI6jsxg=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

{
  "schemaVersion": 1,
  "goal": "verify go.step.sm/crypto/randutil.Hex in pkg:golang/go.step.sm/crypto@v0.89.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/go.step.sm/crypto@v0.89.0"
  ],
  "symbols": [
    "go.step.sm/crypto/randutil.Hex"
  ]
}

package main

import (
	"fmt"
	"os"

	"go.step.sm/crypto/randutil"
)

func main() {
	if err := runTests(); err != nil {
		fmt.Fprintf(os.Stderr, "Contract test failed: %v\n", err)
		os.Exit(1)
	}
	fmt.Println("All contract tests passed successfully.")
}

func runTests() error {
	// 1. Hex returns lowercase hexadecimal string of the requested length
	{
		for _, length := range []int{1, 8, 16, 32, 64} {
			s, err := randutil.Hex(length)
			if err != nil {
				return fmt.Errorf("test 1 failed: Hex(%d) returned error: %w", length, err)
			}
			if len(s) != length {
				return fmt.Errorf("test 1 failed: expected length %d, got %d (string: %q)", length, len(s), s)
			}
		}
	}

	// 2. Hex with zero length returns an empty string without error
	{
		s, err := randutil.Hex(0)
		if err != nil {
			return fmt.Errorf("test 2 failed: Hex(0) returned error: %w", err)
		}
		if s != "" {
			return fmt.Errorf("test 2 failed: expected empty string for length 0, got %q", s)
		}
	}

	// 3. Hex output contains only characters in range 0-9 and a-f
	{
		s, err := randutil.Hex(128)
		if err != nil {
			return fmt.Errorf("test 3 failed: Hex(128) returned error: %w", err)
		}
		for i, c := range s {
			if !((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f')) {
				return fmt.Errorf("test 3 failed: invalid hex character %c at position %d in %q", c, i, s)
			}
		}
	}

	// 4. Hex generates distinct random values across consecutive calls
	{
		s1, err1 := randutil.Hex(32)
		if err1 != nil {
			return fmt.Errorf("test 4 failed: first call to Hex(32) failed: %w", err1)
		}
		s2, err2 := randutil.Hex(32)
		if err2 != nil {
			return fmt.Errorf("test 4 failed: second call to Hex(32) failed: %w", err2)
		}
		if s1 == s2 {
			return fmt.Errorf("test 4 failed: consecutive calls produced identical string: %q", s1)
		}
	}

	return nil
}