text: import assert from 'assert'
  import math from '../../../../src/defaultInstance.js'
  const permutations = math.permutations
  
  describe('permutations', function () {
    it('should calculate the permutations of a number', function () {
      assert.strictEqual(permutations(0), 1)
      assert.strictEqual(permutations(1), 1)
      assert.strictEqual(permutations(2), 2)
      assert.strictEqual(permutations(3), 6)
      assert.strictEqual(permutations(4), 24)
      assert.strictEqual(permutations(5), 120)
    })
  
    it('should calculate the permutations of a BigNumber', function () {
      assert.deepStrictEqual(permutations(math.bignumber(4)), math.bignumber(24))
      assert.deepStrictEqual(permutations(math.bignumber(5)), math.bignumber(120))
      assert.deepStrictEqual(permutations(math.bignumber(8)), math.bignumber(40320))
    })
  
    it('should calculate the permutations of a BigNumber, taking k at a time', function () {
      assert.deepStrictEqual(permutations(math.bignumber(5), math.bignumber(4)), math.bignumber(120))
      assert.deepStrictEqual(permutations(math.bignumber(6), math.bignumber(3)), math.bignumber(120))
      assert.deepStrictEqual(permutations(math.bignumber(9), math.bignumber(8)), math.bignumber(362880))
    })
  
    it('should calculate the permutations of a number, taking k at a time', function () {
      assert.strictEqual(permutations(5, 4), 120)
      assert.strictEqual(permutations(9, 8), 362880)
      assert.strictEqual(permutations(7, 5), 2520)
    })
  
    it('should fail loudly when k is larger than x', function () {
      assert.throws(function () { permutations(5, 6) }, TypeError)
      assert.throws(function () { permutations(math.bignumber(5), math.bignumber(6)) }, TypeError)
    })
  
    it('should not accept negative or non-integer arguments', function () {
      assert.throws(function () { permutations(12, -6) }, TypeError)
      assert.throws(function () { permutations(-12, 6) }, TypeError)
      assert.throws(function () { permutations(4.5, 2) }, TypeError)
      assert.throws(function () { permutations(4, 0.5) }, TypeError)
      assert.throws(function () { permutations(math.bignumber(-12), -6) }, TypeError)
      assert.throws(function () { permutations(math.bignumber(12.5), math.bignumber(6)) }, TypeError)
      assert.throws(function () { permutations(math.bignumber(12.5), math.pi) }, TypeError)
    })
  
    it('should not accept more than two arguments', function () {
      assert.throws(function () { permutations(12, 6, 13) })
      assert.throws(function () { permutations(-12, 6, 13) })
    })
  
    it('should not accept arguments of the wrong type', function () {
      assert.throws(function () { permutations('baa baa black sheep', true) })
      assert.throws(function () { permutations(new Array(12)) })
    })
  
    it('should LaTeX permutations', function () {
      const expression = math.parse('permutations(2)')
      assert.strictEqual(expression.toTex(), '\\mathrm{permutations}\\left(2\\right)')
    })
  })
  