import { describe, expect, it } from "vitest"

import { toCapitalCase } from "./toCapitalCase"

describe("toCapitalCase", () => {
  it("should return same value for null or undefined", () => {
    expect(toCapitalCase(null)).toBe(null)
    expect(toCapitalCase(undefined)).toBe(undefined)
  })

  it("should return empty string for empty input", () => {
    expect(toCapitalCase("")).toBe("")
  })

  it("should capitalize the first letter and lowercase the rest", () => {
    expect(toCapitalCase("hello")).toBe("Hello")
    expect(toCapitalCase("HELLO")).toBe("Hello")
    expect(toCapitalCase("hElLo")).toBe("Hello")
    expect(toCapitalCase("h")).toBe("H")
    expect(toCapitalCase("H")).toBe("H")
  })

  it("should handle strings with spaces", () => {
    expect(toCapitalCase(" hello ")).toBe("Hello")
    expect(toCapitalCase("   ")).toBe("")
  })
})