Write useful test matchers compatible with Jest and Jasmine.
npm install --save-dev add-matchers
Include add-matchers after your test framework but before your tests, and register your matchers before your tests as well.
import { addMatchers } from "add-matchers";
addMatchers({
toBeFoo(value) {
return value === "foo";
},
toInclude(other, value) {
return value.includes(other);
}
});expect("foo").toBeFoo();
expect("jamie").toInclude("jam");import { addMatchers } from "add-matchers";
addMatchers.asymmetric({
toBeFoo(value) {
return value === "foo";
},
toInclude(other, value) {
return value.includes(other);
}
});expect({ key: "foo", prop: "bar" }).toEqual({
key: any.toBeFoo(),
prop: any.toInclude("ar")
});The argument passed to expect is always the last argument passed to your Matcher, with any other arguments appearing before it in the order they were supplied.
This means that, in the case of expect(received).toBeAwesome(arg1, arg2, arg3), your function will be called with fn(arg1, arg2, arg3, received).
Arguments are ordered in this way to support partial application and increase re-use of matchers.
If we wanted to use the following Matchers in our tests;
// matcher with 0 arguments
expect(4).toBeEvenNumber();
// matcher with 1 argument
expect({}).toBeOfType("Object");
// matcher with Many arguments
expect([100, 14, 15, 2]).toContainItems(2, 15, 100);We would create them as follows;
import { addMatchers } from "add-matchers";
addMatchers({
// matcher with 0 arguments
toBeEvenNumber: function(received) {
// received : 4
return received % 2 === 0;
},
// matcher with 1 argument
toBeOfType: function(type, received) {
// type : 'Object'
// received : {}
return Object.prototype.toString.call(received) === "[object " + type + "]";
},
// matcher with many arguments
toContainItems: function(arg1, arg2, arg3, received) {
// arg1 : 2
// arg2 : 15
// arg3 : 100
// received : [100, 14, 15, 2]
return (
received.indexOf(arg1) !== -1 &&
received.indexOf(arg2) !== -1 &&
received.indexOf(arg3) !== -1
);
}
});For more examples, see Jasmine Matchers which is built using this library.
Get help with issues by creating a Bug Report or discuss ideas by opening a Feature Request.
If you find my Open Source projects useful, please share them ❤️
- eslint-formatter-git-log
ESLint Formatter featuring Git Author, Date, and Hash - eslint-plugin-move-files
Move and rename files while keeping imports up to date - eslint-plugin-prefer-arrow-functions
Convert functions to arrow functions - ImageOptim-CLI
Automates ImageOptim, ImageAlpha, and JPEGmini for Mac to make batch optimisation of images part of your automated build process. - Jasmine-Matchers
Write Beautiful Specs with Custom Matchers - karma-benchmark
Run Benchmark.js over multiple Browsers, with CI compatible output - self-help
Interactive Q&A Guides for Web and the Command Line - syncpack
Manage multiple package.json files, such as in Lerna Monorepos and Yarn Workspaces
I'm Jamie Mason from Leeds in England, I began Web Design and Development in 1999 and have been Contracting and offering Consultancy as Fold Left Ltd since 2012. Who I've worked with includes Sky Sports, Sky Bet, Sky Poker, The Premier League, William Hill, Shell, Betfair, and Football Clubs including Leeds United, Spurs, West Ham, Arsenal, and more.
