EulerMethod.test.js

import { eulerFull, eulerStep } from '../EulerMethod'

describe('eulerStep', () => {
  it('should calculate the next y value correctly', () => {
    expect(
      eulerStep(0, 0.1, 0, function (x, y) {
        return x
      })
    ).toBe(0)
    expect(
      eulerStep(2, 1, 1, function (x, y) {
        return x * x
      })
    ).toBe(5)
  })
})

describe('eulerFull', () => {
  it('should return all the points found', () => {
    expect(
      eulerFull(0, 3, 1, 0, function (x, y) {
        return x
      })
    ).toEqual([
      { x: 0, y: 0 },
      { x: 1, y: 0 },
      { x: 2, y: 1 },
      { x: 3, y: 3 }
    ])

    expect(
      eulerFull(3, 4, 0.5, 1, function (x, y) {
        return x * x
      })
    ).toEqual([
      { x: 3, y: 1 },
      { x: 3.5, y: 5.5 },
      { x: 4, y: 11.625 }
    ])
  })
})