• ❤️ Data Tables
• 🛀 Clean tests
• 🎉 Multiple tests written once
• 💪 Optional given, when, then API

Writing clean descriptive tests can sometimes be difficult and cumbersome.

This plugin provides syntactic sugar to make writing well documented data driven tests easy and enjoyable.

Data Driven Testing is when we test the same behavior multiple times with different parameters and assertions, babel-plugin-gwt's data driven testing support makes this a first class feature.

babel-plugin-gwt gives your standard Javascript tests four new blocks given, when, then, where (you can continue to use whichever test runner and assertion library that you like with this plugin).

• given, when, then blocks are used to generate your test title making it easier to write, read and maintain your test.

• Data Tables are supported with the where block used to write test data for your test to be ran multiple times with different inputs.

With npm:

npm install --save-dev babel-plugin-gwt

With yarn:

yarn add -D babel-plugin-gwt

{
  "plugins": ["babel-plugin-gwt"]
}

babel --plugins babel-plugin-gwt script.js

require('babel-core').transform('code', {
  plugins: ['babel-plugin-gwt'],
})

A simple test with babel-plugin-gwt could look something like:

it('add', () => {
  given: 'a and b'
  const a = 1;
  const b = 1;

  when: 'added'
  const actual = a   b;

  then: 'returns 2'
  expect(actual).toBe(2);
});

↓ ↓ ↓ ↓ ↓ ↓

This test can become more powerful by using the where block to run the same test multiple times with different data. The where block allows you to define variables that are available anywhere in the test and to use the $ symbol in your test title and given, when, then blocks to interpolate values into the generated test title.

it('add', () => {
  when: '$a is added to $b'
  const actual = a   b;

  then: '$expected is returned'
  expect(actual).toBe(expected);

  where: {
    a | b || expected
    0 | 0 || 0
    1 | 0 || 1
    0 | 1 || 1
    1 | 1 || 2
  }
});

↓ ↓ ↓ ↓ ↓ ↓

All label blocks are optional, and some like given may not make sense for every test.

The given block is used to describe the inputs of your test.

• Arguments: String

Example: given: 'some input'

The when block is used to describe the behaviour being tested.

• Arguments: String

Example: when: 'something happens'

The then block is used to describe the assertions being made.

• Arguments: String

Example: then: 'it should be ...'

The where block is used to supply your test with a data table. The table must have the following structure:

• The first row must be variable names you wish to use within the test. These will be hoisted into the whole scope of the test block and so can be used anywhere inside of the test.
• All other rows can be data and variables available in the outer scope that you may be testing
• Columns of data are separated with |, a convention is to use two pipes (||) for any expected values (although this is just a convention under the hood both | and || are treated the same).

Example:

  where: {
    a | b || expected
    0 | 0 || 0
    1 | 0 || 1
    0 | 1 || 1
    1 | 1 || 2
  }

All description blocks (given, when, and then) and the usual test description can add values to be interpolated with the $ symbol infront of the variable name defined in the where block table.

babel-plugin-gwt supports all of the following test blocks: it, fit, xit, it.only, it.skip, test, ftest, xtest, test.only, test.skip.

That means that the following frameworks are supported:

• Jest
• Ava
• Moca
• Tape
• Cypress
• Other? Send PR to add 🙌

Some of the syntaxes used within this plugin will more than likely upset most linters so it is probably advisable to disable them within the tests using babel-plugin-gwt.

For example eslint:

it('add', () => {
  /* eslint-disable no-undef, no-unused-labels */
  when: '$a is added to $b'
  const actual = a   b;

  then: '$expected is returned'
  expect(actual).toBe(expected);

  where: {
    a | b || expected
    0 | 0 || 0
    1 | 0 || 1
    0 | 1 || 1
    1 | 1 || 2
  }
});

Within the where block the first column does not support Object({}) or Array ([]) literals

Not supported:

where: {
  obj  | key   | value || expected
  {}   | 'foo' | 'bar' || { foo: 'bar' }
}

Supported:

where: {
  key  | obj | value || expected
  'foo'| {}  | 'bar' || { foo: 'bar' }
}

• jest-each
• mocha-each

Matt Phillips 💻 📖 💡 🤔 ⚠️

MIT