rescript-test

ReScriptTest

A lightweight test framework for ReScript

Check out the documentation!

Installation

Run the following in your console:

$ yarn add --dev rescript-test

Then add rescript-test to your bsconfig.json's bs-dev-dependencies:

 {
   "bs-dev-dependencies": [
+    "rescript-test",
   ]
 }

Usage

$ # All tests
$ retest 'test/**/*.bs.js'
$ # Single file
$ retest 'test/MyTest.bs.js'

Testing with DOM

The test framework can simulate a browser using JSDOM, to activate it, simply add the --with-dom option.

$ # All tests
$ retest --with-dom 'test/**/*.bs.js'
$ # Single file
$ retest --with-dom 'test/MyTest.bs.js'

Basics

open Test

let intEqual = (~message=?, a: int, b: int) =>
  assertion(~message?, ~operator="intEqual", (a, b) => a === b, a, b)

let stringEqual = (~message=?, a: string, b: string) =>
  assertion(~message?, ~operator="stringEqual", (a, b) => a == b, a, b)

test("Equals", () => {
  let a = 1
  let b = 1
  intEqual(a, b)
})

let isCharCode = (a, b) => {
  a->String.charCodeAt(0) === b
}

test("Custom comparator", () => {
  let a = "a"

  assertion(~message="Char code should match", ~operator="isCharCode", isCharCode, a, 97.0)
  assertion(~message="Char code should match", ~operator="isCharCode", isCharCode, a, 98.0)
})

type user = {username: string, id: string}

let userEq = (a, b) => a.id === b.id
let userEqual = (~message=?, a: user, b: user) =>
  assertion(~message?, ~operator="userEqual", userEq, a, b)

test("DeepEquals", () => {
  let a = {username: "user", id: "a"}
  let b = {username: "user", id: "a"}
  stringEqual(a.username, b.username)
  userEqual(a, b)
})

Outputs:

1/4: Equals
  PASS - No message
2/4: Custom comparator
  PASS - Char code should match
  FAIL - Char code should match
    ---
    operator: isCharCode
    left:  a
    right: 98
    ...
3/4: DeepEquals
  PASS - No message
  PASS - No message
4/4: Async
  PASS - No message

# Ran 4 tests (6 assertions)
# 3 passed
# 1 failed

API

Tests

• test(name, body)
• createTestWith(~setup: unit => 'a, ~teardown: 'a => unit=? -> test
• testAsync(name, body)
• createTestAsyncWith(~setup: unit => 'a, ~teardown: 'a => unit=?, name, body: ('a, cb) => unit) -> testAsync

Operators

• throws(func, ~message: string=?, ~test: exn => bool=?)
• doesNotThrow(func, ~message: string=?)
• assertion(comparator, a, b, ~operator: string=?, ~message: string=?)
• pass()
• fail()
• todo(string)

Creating assertion shorthands

let stringMapEqual = (~message=?, a, b) =>
  assertion(
    ~message?,
    ~operator="stringMapEqual",
    (a, b) => Belt.Map.String.eq(a, b, (a, b) => a === b),
    a,
    b,
  )

Generic equal/deepEqual (not recommended)

Those that be useful to transition from an existing testing library, but we do not recommend polymorphic checks.

let equal = (~message=?, a, b) => assertion(~message?, ~operator="equal", (a, b) => a === b, a, b)

let deepEqual = (~message=?, a, b) =>
assertion(~message?, ~operator="deepEqual", (a, b) => a == b, a, b)

Create tests with setup and teardown

The setup function returns a clean context for the test, the teardown function resets it.

let testWithRef = createTestWith(~setup=() => ref(0), ~teardown=someRef => someRef := 0)

testWithRef("Setup & teardown", someRef => {
  incr(someRef)
  equal(someRef.contents, 1)
})

If you want to test with React, you can add the following helper as your test utility file:

@bs.val external window: {..} = "window"
@bs.send external remove: Dom.element => unit = "remove"

let createContainer = () => {
  let containerElement: Dom.element = window["document"]["createElement"]("div")
  let _ = window["document"]["body"]["appendChild"](containerElement)
  containerElement
}

let cleanupContainer = container => {
  ReactDOM.unmountComponentAtNode(container)
  remove(container)
}

let testWithReact = createTestWith(~setup=createContainer, ~teardown=cleanupContainer)
let testAsyncWithReact = createTestAsyncWith(~setup=createContainer, ~teardown=cleanupContainer)

And then use it:

testWithReact("Can render", container => {
  act(() =>
    ReactDOMRe.render(
      <div> {"hello"->React.string} </div>,
      container,
    )
  )

  let div = container->DOM.findBySelectorAndTextContent("div", "hello")
  isTrue(div->Option.isSome)
})

Async assertion count plan

testAsync("My test", (cb) => (
  // your tests
  cb(~planned=2, ())
))

Env file

Add a retest.env.js to your project root directory for any setup.