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Testing with cds.test ​

Overview ​

The cds.test library provides best practice utils for writing tests for CAP Node.js applications.

Install it with:

sh
npm add -D @cap-js/cds-test

Examples

Find examples in cap/samples and in the SFlight sample.

Running a CAP Server ​

Use function cds.test() to easily launch and test a CAP server. For example, given your CAP application has a ./test subfolder containing tests as follows:

zsh
project/    # your project's root folder
├─ srv/
├─ db/
├─ test/    # your .test.js files go in here
└─ package.json

Start your app's server in your .test.js files like that:

js
const cds = require('@sap/cds')
describe(()=>{
  const test = cds.test(__dirname+'/..')
})

This launches a server from the specified target folder in a beforeAll() hook, with controlled shutdown when all tests have finished in an afterAll() hook.

Don't use process.chdir()!

Doing so in Jest tests may leave test containers in failed state, leading to failing subsequent tests. Use cds.test.in() instead.

Don't load cds.env before cds.test()!

To ensure cds.env, and hence all plugins, are loaded from the test's target folder, the call to cds.test() is the first thing you do in your tests. Any references to cds sub modules or any imports of which have to go after. → Learn more in CDS_TEST_ENV_CHECK.

Testing Service APIs ​

As cds.test() launches the server in the current process, you can access all services programmatically using the respective Node.js Service APIs. Here's an example for that taken from cap/samples:

js
it('Allows testing programmatic APIs', async () => {
  const AdminService = await cds.connect.to('AdminService')
  const { Authors } = AdminService.entities
  expect (await SELECT.from(Authors))
  .to.eql(await AdminService.read(Authors))
  .to.eql(await AdminService.run(SELECT.from(Authors)))
})

Testing HTTP APIs ​

To test HTTP APIs, we can use bound functions like so:

js
const { GET, POST } = cds.test(...)
const { data } = await GET ('/browse/Books')
await POST (`/browse/submitOrder`, { book: 201, quantity: 5 })

Learn more in GET/PUT/POST.

Authenticated Endpoints ​

cds.test() uses the standard authentication strategy in development mode, which is the mocked authentication. This also includes the usage of pre-definded mock users

You can set the user for an authenticated request like this:

js
await GET('/admin/Books', { auth: { username: 'alice', password: '' } })

This is the same as setting the HTTP Authorization header with values for basic authentication:

http
GET http://localhost:4004/admin/Books
Authorization: Basic alice:

Learn how to explicitly configure mock users in your package.json file.

Using Jest or Mocha ​

Mocha and Jest are the most used test runners at the moment, with each having its user base.

The cds.test library is designed to allow you to write tests that can run with both. Here's an example:

js
describe('my test suite', ()=>{
  const { GET, expect } = cds.test(...)
  it ('should test', ()=>{   // Jest & Mocha
    const { data } = await GET ('/browse/Books')
    expect(data.value).to.eql([ // chai style expect
      { ID: 201, title: 'Wuthering Heights', author: 'Emily Brontë' },
      { ID: 252, title: 'Eleonora', author: 'Edgar Allen Poe' },
      //...
    ])
  })
})

To ensure that your tests run with both jest and mocha, start a test server with cds.test(...) inside a describe block of the test.

You can use Mocha-style before/after or Jest-style beforeAll/afterAll in your tests, as well as the common describe, test, it methods. In addition, to be portable, you should use the Chai Assertion Library's variant of expect.

All tests in cap/samples are written in that portable way.

Run them with npm run jest or with npm run mocha.

Helpers can cause conflicts

jest helpers might cause conflicts with the generic implementation of @sap/cds.

To avoid such conflicts, do not use the following helpers:

  • jest.resetModules as it leaves the server in an inconsistent state.
  • jest.useFakeTimers as it intercepts the server shutdown causing test timeouts.

Using Test Watchers ​

You can also start the tests in watch mode, for example:

sh
jest --watchAll

This should give you green tests, when running in cap/samples root:

PASS  test/cds.ql.test.js
PASS  test/hierarchical-data.test.js
PASS  test/hello-world.test.js
PASS  test/messaging.test.js
PASS  test/consuming-services.test.js
PASS  test/custom-handlers.test.js
PASS  test/odata.test.js
PASS  test/localized-data.test.js

Test Suites: 8 passed, 8 total
Tests:       65 passed, 65 total
Snapshots:   0 total
Time:        3.611 s, estimated 4 s
Ran all test suites.

Similarly, you can use other test watchers like mocha -w.

Class cds.test.Test ​

Instances of this class are returned by cds.test(), for example:

js
const test = cds.test(_dirname)

You can also use this class and create instances yourself, for example, like that:

js
const { Test } = cds.test
let test = new Test
test.run().in(_dirname)

cds.test() ​

This method is the most convenient way to start a test server. It's actually just a convenient shortcut to construct a new instance of class Test and call test.run(), defined as follows:

js
const { Test } = cds.test
cds.test = (...args) => (new Test).run(...args)

Run cds.test once per test file

@sap/cds relies on server state like cds.model. Running cds.test multiple times within the same test file can lead to a conflicting state and erratic behavior.

.chai, ... ​

To write tests that run in Mocha as well as in Jest, you should use the Chai Assertion Library through the following convenient methods.

Using chai requires these dependencies added to your project:

sh
npm add -D chai@4 chai-as-promised@7 chai-subset jest

.expect ​

Shortcut to the chai.expect() function, used like that:

js
const { expect } = cds.test(), foobar = {foo:'bar'}
it('should support chai.except style', ()=>{
  expect(foobar).to.have.property('foo')
  expect(foobar.foo).to.equal('bar')
})

If you prefer Jest's expect() functions, you can just use the respective global:

js
cds.test()
it('should use jest.expect', ()=>{
  expect({foo:'bar'}).toHaveProperty('foo')
})

.assert ​

Shortcut to the chai.assert() function, used like that:

js
const { assert } = cds.test(), foobar = {foo:'bar'}
it('should use chai.assert style', ()=>{
  assert.property(foobar,'foo')
  assert.equal(foobar.foo,'bar')
})

.should ​

Shortcut to the chai.should() function, used like that:

js
const { should } = cds.test(), foobar = {foo:'bar'}
it('should support chai.should style', ()=>{
  foobar.should.have.property('foo')
  foobar.foo.should.equal('bar')
  should.equal(foobar.foo,'bar')
})

.chai ​

This getter provides access to the chai library, preconfigured with the chai-subset and chai-as-promised plugins. These plugins contribute the containSubset and eventually APIs, respectively. The getter is implemented like this:

js
get chai() {
  return require('chai')
  .use (require('chai-subset'))
  .use (require('chai-as-promised'))
}

.axios ​

Provides access to the Axios instance used as HTTP client. It comes preconfigured with the base URL of the running server, that is, http://localhost:<port>. This way, you only need to specify host-relative URLs in tests, like /catalog/Books.

Using axios requires adding this dependency:

sh
npm add -D axios

GET / PUT / POST ... ​

These are bound variants of the test.get/put/post/... methods allowing to write HTTP requests like that:

js
const { GET, POST } = cds.test()
const { data } = await GET('/browse/Books')
await POST('/browse/submitOrder',
  { book:201, quantity:1 },
  { auth: { username: 'alice' }}
)

Learn more about Axios.

For single URL arguments, the functions can be used in tagged template string style, which allows omitting the parentheses from function calls:

js
let { data } = await GET('/browse/Books')
let { data } = await GET `/browse/Books`

test. get/put/post/...() ​

These are mirrored version of the corresponding methods from axios, which prefix each request with the started server's url and port, which simplifies your test code:

js
const test = cds.test() //> served at localhost with an arbitrary port
const { data } = await test.get('/browse/Books')
await test.post('/browse/submitOrder',
  { book:201, quantity:1 },
  { auth: { username: 'alice' }}
)

Learn more about Axios.

test .data .reset() ​

This is a bound method, which can be used in a beforeEach handler to automatically reset and redeploy the database for each test like so:

js
const { test } = cds.test()
beforeEach (test.data.reset)

Instead of using the bound variant, you can also call this method the standard way:

js
beforeEach (async()=>{
  await test.data.reset() 
  //...
})

test. log() ​

Allows to capture console output in the current test scope. The method returns an object to control the captured logs:

tsx
function cds.test.log() => {
  output : string
  clear()
  release()
}

Usage examples:

js
describe('cds.test.log()', ()=>{
  let log = cds.test.log()

  it ('should capture log output', ()=>{
    expect (log.output.length).to.equal(0)
    console.log('foo',{bar:2})
    expect (log.output.length).to.be.greaterThan(0)
    expect (log.output).to.contain('foo')
  })

  it('should support log.clear()', ()=> {
    log.clear()
    expect (log.output).to.equal('')
  })

  it('should support log.release()', ()=> {
    log.release() // releases captured log
    console.log('foobar') // not captured
    expect (log.output).to.equal('')
  })
})

The implementation redirects any console operations in a beforeAll() hook, clears log.output before each test, and releases the captured console in an afterAll() hook.

test. run (...) ​

This is the method behind cds.test() to start a CDS server, that is the following are equivalent:

js
cds.test(...)
js
(new cds.test.Test).run(...)

It asynchronously launches a CDS server in a beforeAll() hook with an arbitrary port, with controlled shutdown when all tests have finished in an afterAll() hook.

The arguments are the same as supported by the cds serve CLI command.

Specify the command 'serve' as the first argument to serve specific CDS files or services:

js
cds.test('serve','srv/cat-service.cds')
cds.test('serve','CatalogService')

You can optionally add test.in(folder) in fluent style to run the test in a specific folder:

js
cds.test('serve','srv/cat-service.cds').in('/cap/samples/bookshop')

If the first argument is not 'serve', it's interpreted as a target folder:

js
cds.test('/cap/samples/bookshop')

This variant is a convenient shortcut for:

js
cds.test('serve','all','--in-memory?').in('/cap/samples/bookshop')
cds.test().in('/cap/samples/bookshop') //> equivalent

test. in (folder, ...) ​

Safely switches cds.root to the specified target folder. Most frequently you'd use it in combination with starting a server with cds.test() in fluent style like that:

js
let test = cds.test(...).in(__dirname)

It can also be used as static method to only change cds.root without starting a server:

js
cds.test.in(__dirname)

CDS_TEST_ENV_CHECK ​

It's important to ensure cds.env, and hence all plugins, are loaded from the test's target folder. To ensure this, any references to or imports of cds sub modules have to go after all plugins are loaded. For example if you had a test like that:

js
cds.env.fiori.lean_draft = true   //> cds.env loaded from ./
cds.test(__dirname)               //> target folder: __dirname

This would result in the test server started from __dirname, but erroneously using cds.env loaded from ./.

As these mistakes end up in hard-to-resolve follow up errors, test.in() can detect this if environment variable CDS_TEST_ENV_CHECK is set. The previous code will then result into an error like that:

sh
CDS_TEST_ENV_CHECK=y jest cds.test.test.js
zsh
Detected cds.env loaded before running cds.test in different folder:
1. cds.env loaded from:  ./
2. cds.test running in:  cds/tests/bookshop

    at Test.in (node_modules/@sap/cds/lib/utils/cds-test.js:65:17)
    at test/cds.test.test.js:9:41
    at Object.describe (test/cds.test.test.js:5:1)

   5 | describe('cds.test', ()=>{
>  6 |   cds.env.fiori.lean_draft = true
     |       ^
   7 |   cds.test(__dirname)

  at env (test/cds.test.test.js:7:7)
  at Object.describe (test/cds.test.test.js:5:1)

A similar error would occur if one of the cds sub modules would be accessed, which frequently load cds.env in their global scope, like cds.Service in the following snippet:

js
class MyService extends cds.Service {}  //> cds.env loaded from ./
cds.test(__dirname)                     //> target folder: __dirname

To fix this, always ensure your calls to cds.test.in(folder) or cds.test(folder) goes first, before anything else loading cds.env:

js
cds.test(__dirname) //> always should go first
// anything else goes after that:
cds.env.fiori.lean_draft = true
class MyService extends cds.Service {}

Do switch on CDS_TEST_ENV_CHECK !

We recommended to switch on CDS_TEST_ENV_CHECK in all your tests to detect such errors. It's likely to become default in upcoming releases.

Best Practices ​

Check Status Codes Last ​

Avoid checking for single status codes. Instead, simply check the response data:

js
const { data, status } = await GET `/catalog/Books`
expect(status).to.equal(200)   //> DON'T do that upfront
expect(data).to.equal(...)     //> do this to see what's wrong
expect(status).to.equal(200)   //> Do it at the end, if at all

This makes a difference if there are errors: with the status code check, your test aborts with a useless Expected: 200, received: xxx error, while without it, it fails with a richer error that includes a status text.

Note that by default, Axios throws errors for status codes < 200 and >= 300. This can be configured, though.

Minimal Assumptions ​

When checking expected errors messages, only check for significant keywords. Don't hardwire the exact error text, as this might change over time, breaking your test unnecessarily.

DON'T hardwire on overly specific error messages:

js
await expect(POST(`/catalog/Books`,...)).to.be.rejectedWith(
  'Entity "CatalogService.Books" is readonly'
)

DO check for the essential information only:

js
await expect(POST(`/catalog/Books`,...)).to.be.rejectedWith(
  /readonly/i
)

Keep Test Code Environment Agnostic ​

Environment setup shouldn't be part of the test code itself. That should be handled by setup scripts like CI/CD pipelines. This way, your tests remain isolated and reproducible across different setups.

js
// NO service bindings, env. variables, profiles, etc. here
// Do this outside in setup scripts etc.
describe(() => { cds.test(...) })

Learn how to setup integration tests with cds bind.

Using cds.test in REPL ​

You can use cds.test in REPL, for example, by running this from your command line in cap/samples:

sh
[cap/samples] cds repl
Welcome to cds repl v7.1
js
> var test = await cds.test('bookshop')
log
[cds] - model loaded from 6 file(s):

  ./bookshop/db/schema.cds
  ./bookshop/srv/admin-service.cds
  ./bookshop/srv/cat-service.cds
  ./bookshop/app/services.cds
  ./../../cds/common.cds
  ./common/index.cds

[cds] - connect to db > sqlite { database: ':memory:' }
 > filling sap.capire.bookshop.Authors from ./bookshop/db/data/sap.capire.bookshop-Authors.csv
 > filling sap.capire.bookshop.Books from ./bookshop/db/data/sap.capire.bookshop-Books.csv
 > filling sap.capire.bookshop.Books.texts from ./bookshop/db/data/sap.capire.bookshop-Books_texts.csv
 > filling sap.capire.bookshop.Genres from ./bookshop/db/data/sap.capire.bookshop-Genres.csv
 > filling sap.common.Currencies from ./common/data/sap.common-Currencies.csv
 > filling sap.common.Currencies.texts from ./common/data/sap.common-Currencies_texts.csv
/> successfully deployed to sqlite in-memory db

[cds] - serving AdminService { at: '/admin', impl: './bookshop/srv/admin-service.js' }
[cds] - serving CatalogService { at: '/browse', impl: './bookshop/srv/cat-service.js' }

[cds] - server listening on { url: 'http://localhost:64914' }
[cds] - launched at 9/8/2021, 5:36:20 PM, in: 767.042ms
[ terminate with ^C ]
js
> await SELECT `title` .from `Books` .where `exists author[name like '%Poe%']`
[ { title: 'The Raven' }, { title: 'Eleonora' } ]
js
> var { CatalogService } = cds.services
> await CatalogService.read `title, author` .from `ListOfBooks`
[
  { title: 'Wuthering Heights', author: 'Emily Brontë' },
  { title: 'Jane Eyre', author: 'Charlotte Brontë' },
  { title: 'The Raven', author: 'Edgar Allen Poe' },
  { title: 'Eleonora', author: 'Edgar Allen Poe' },
  { title: 'Catweazle', author: 'Richard Carpenter' }
]

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