golang.org/x/text v0.16.0: cases.Caser

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 golang.org/x/text/cases.Caser in pkg:golang/golang.org/x/text@v0.16.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/text@v0.16.0
Demonstrate these symbols/APIs:
  - golang.org/x/text/cases.Caser

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:sha256:7c0a1a9f8ce39e85a1d9ad394170eef9f38e2b386503f24e70c57110cc4814b1","contract":["Title Caser converts text to title case using language-specific rules","Upper Caser converts text to uppercase using language-specific rules","Lower Caser converts text to lowercase using language-specific rules","Caser String method transforms string input","Caser Bytes method transforms byte slice input","Upper Caser for Turkish converts lowercase i to dotted uppercase I","Lower Caser for Turkish converts uppercase I to dotless lowercase i","Title Caser with NoLower preserves uppercase characters in words","Fold Caser performs case folding for case-insensitive matching"],"goal":"verify golang.org/x/text/cases.Caser in pkg:golang/golang.org/x/text@v0.16.0","kind":"HOW","packages":["pkg:golang/golang.org/x/text@v0.16.0"],"schemaVersion":1,"symbols":["golang.org/x/text/cases.Caser"]},"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/golang.org/x/text@v0.16.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/text@v0.16.0","symbols":["golang.org/x/text/cases.Caser"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/text v0.16.0

golang.org/x/text v0.16.0 h1:a94ExnEXNtEwYLGJSIUxnWoxoRz/ZcCsV63ROupILh4=
golang.org/x/text v0.16.0/go.mod h1:GhwF1Be+LQoKShO3cGOHzqOgRrGaYc9AvblQOmPVHnI=

package main

import (
	"fmt"

	"golang.org/x/text/cases"
	"golang.org/x/text/language"
)

func main() {
	enTitle := cases.Title(language.English)
	enUpper := cases.Upper(language.English)
	trUpper := cases.Upper(language.Turkish)

	sample := "the quick brown fox"
	fmt.Println("Title:", enTitle.String(sample))
	fmt.Println("Upper:", enUpper.String(sample))
	fmt.Println("Turkish Upper:", trUpper.String("istanbul"))
}

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/text/cases.Caser in pkg:golang/golang.org/x/text@v0.16.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/text@v0.16.0"
  ],
  "symbols": [
    "golang.org/x/text/cases.Caser"
  ]
}

package main

import (
	"bytes"
	"fmt"
	"os"

	"golang.org/x/text/cases"
	"golang.org/x/text/language"
)

func main() {
	// 1. Title Caser converts text to title case using language-specific rules
	titleCaser := cases.Title(language.English)
	if got := titleCaser.String("the quick brown fox"); got != "The Quick Brown Fox" {
		fmt.Fprintf(os.Stderr, "Assertion 1 failed: expected 'The Quick Brown Fox', got %q\n", got)
		os.Exit(1)
	}

	// 2. Upper Caser converts text to uppercase using language-specific rules
	upperCaser := cases.Upper(language.English)
	if got := upperCaser.String("hello world"); got != "HELLO WORLD" {
		fmt.Fprintf(os.Stderr, "Assertion 2 failed: expected 'HELLO WORLD', got %q\n", got)
		os.Exit(1)
	}

	// 3. Lower Caser converts text to lowercase using language-specific rules
	lowerCaser := cases.Lower(language.English)
	if got := lowerCaser.String("HELLO WORLD"); got != "hello world" {
		fmt.Fprintf(os.Stderr, "Assertion 3 failed: expected 'hello world', got %q\n", got)
		os.Exit(1)
	}

	// 4. Caser String method transforms string input
	if got := titleCaser.String("golang"); got != "Golang" {
		fmt.Fprintf(os.Stderr, "Assertion 4 failed: expected 'Golang', got %q\n", got)
		os.Exit(1)
	}

	// 5. Caser Bytes method transforms byte slice input
	inputBytes := []byte("golang")
	if got := titleCaser.Bytes(inputBytes); !bytes.Equal(got, []byte("Golang")) {
		fmt.Fprintf(os.Stderr, "Assertion 5 failed: expected 'Golang', got %q\n", string(got))
		os.Exit(1)
	}

	// 6. Upper Caser for Turkish converts lowercase i to dotted uppercase I
	trUpper := cases.Upper(language.Turkish)
	if got := trUpper.String("istanbul"); got != "İSTANBUL" {
		fmt.Fprintf(os.Stderr, "Assertion 6 failed: expected 'İSTANBUL', got %q\n", got)
		os.Exit(1)
	}

	// 7. Lower Caser for Turkish converts uppercase I to dotless lowercase i
	trLower := cases.Lower(language.Turkish)
	if got := trLower.String("ISTANBUL"); got != "ıstanbul" {
		fmt.Fprintf(os.Stderr, "Assertion 7 failed: expected 'ıstanbul', got %q\n", got)
		os.Exit(1)
	}

	// 8. Title Caser with NoLower preserves uppercase characters in words
	titleNoLower := cases.Title(language.English, cases.NoLower)
	if got := titleNoLower.String("iPhone and iPad"); got != "IPhone And IPad" {
		fmt.Fprintf(os.Stderr, "Assertion 8 failed: expected 'IPhone And IPad', got %q\n", got)
		os.Exit(1)
	}

	// 9. Fold Caser performs case folding for case-insensitive matching
	folder := cases.Fold()
	if got1, got2 := folder.String("Straße"), folder.String("STRASSE"); got1 != got2 {
		fmt.Fprintf(os.Stderr, "Assertion 9 failed: expected matching case folding for Straße/STRASSE, got %q vs %q\n", got1, got2)
		os.Exit(1)
	}

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