mathjs/test/unit-tests/expression/transform/diff.transform.test.js

import assert from 'assert'
import math from '../../../../src/defaultInstance.js'

const diff = math.expression.transform.diff

describe('diff.transform', function () {
  it('Should use one-based indexing for dimensions with arrays', function () {
    // With Dim = 1
    assert.deepStrictEqual(diff([1, 2, 4, 7, 0], 1), [1, 2, 3, -7])
    assert.deepStrictEqual(diff([1, 2, 4, 7, 0], math.bignumber(1)), [1, 2, 3, -7])

    // Without Dim = 1
    assert.deepStrictEqual(diff([1, 2, 4, 7, 0]), [1, 2, 3, -7])
  })

  it('Should use one-based indexing for dimensions with matrices', function () {
    // With Dim = 1
    assert.deepStrictEqual(diff(math.matrix([1, 2, 4, 7, 0]), 1), math.matrix([1, 2, 3, -7]))
    assert.deepStrictEqual(diff(math.matrix([1, 2, 4, 7, 0]), math.bignumber(1)), math.matrix([1, 2, 3, -7]))

    // Without Dim = 1
    assert.deepStrictEqual(diff(math.matrix([1, 2, 4, 7, 0])), math.matrix([1, 2, 3, -7]))
  })

  it('should throw an error if the dimension is below the range for one based indices', function () {
    assert.throws(function () { diff(math.matrix([1, 2, 4, 7, 0]), 0) }, Error)
  })

  it('should throw an error if the dimension is above the range for one based indices', function () {
    assert.throws(function () { diff(math.matrix([1, 2, 4, 7, 0]), math.bignumber(0)) }, Error)
  })

  it('should work with the parser', function () {
    assert.deepStrictEqual(math.evaluate('diff([1, 2, 4, 7, 0], 1)'), math.matrix([1, 2, 3, -7]))
  })
})