import assert from 'assert'
import math from '../../../../src/defaultInstance.js'
const bellNumbers = math.bellNumbers

describe('bellNumbers', function () {
  it('should calculate the number of partitions of a set', function () {
    assert.strictEqual(bellNumbers(3), 5)
    assert.strictEqual(bellNumbers(0), 1)
    assert.strictEqual(bellNumbers(8), 4140)
  })

  it('should calculate the bellNumbers of n items with BigNumbers', function () {
    assert.deepStrictEqual(bellNumbers(math.bignumber(2)), math.bignumber(2))
    assert.deepStrictEqual(bellNumbers(math.bignumber(3)), math.bignumber(5))
  })

  it('should not work with non-integer and negative input', function () {
    assert.throws(function () { bellNumbers(0.5) }, TypeError)
    assert.throws(function () { bellNumbers(-1) }, TypeError)
    assert.throws(function () { bellNumbers(math.bignumber(-3)) }, TypeError)
    assert.throws(function () { bellNumbers(math.bignumber(3.5)) }, TypeError)
  })

  it('should throw an error in case of non-integer input', function () {
    assert.throws(function () { bellNumbers(5.2) }, /Non-negative integer value expected/)
  })

  it('should throw an error in case of negative input', function () {
    assert.throws(function () { bellNumbers(-2) }, /Non-negative integer value expected/)
  })

  it('should throw an error in case of wrong number or type of arguments', function () {
    assert.throws(function () { bellNumbers(5, 3, 2) })
    assert.throws(function () { bellNumbers(true, 'hello world') })
  })

  it('should LaTeX bellNumbers', function () {
    const expression = math.parse('bellNumbers(3)')
    assert.strictEqual(expression.toTex(), '\\mathrm{B}_{3}')
  })
})