Use Jest (Jasmine) and supertest to test REST API.

jest-suppertest.js

// Need to run test async and use jest/jasmine done.fail to let it know when an assertion did not work.
const routerUnderTest = require('../../client_api')
const httptest = require('supertest')
const express = require('express')

const app = express()
app.use('/', routerUnderTest)

describe('I can use the REST api', () => {
  it('displays text for the landing page', (done) => {
    httptest(app)
      .get('/')
      .end((err, res) => {
        try {
          expect(err).toBeNull()
          expect(res.status).toEqual(200)
          expect(res.text).toEqual('You have reached the SPDZ Rest interface. See ....')
          done()
        } catch (err) {
          done.fail(err)
        }
      })
  })
})

// To wrap the horrible try catch block can use
const supertestWithJest = (err, res, done, asserts) => {
  try {
    expect(err).toBeNull()
    asserts()
    done()
  } catch (err) {
    done.fail(err)
  }
}

describe('I can use the REST api', () => {
  it('displays text for the landing page', (done) => {
    httptest(app)
      .get('/')
      .end((err, res) => {
        supertestWithJest(err, res, done, () => {
          expect(res.status).toEqual(200)
          expect(res.text).toEqual('You have reached the SPDZ Rest interface. See ....')
        })
      })
  })
})