JarCastingadd-matchers
Write useful test matchers compatible with Jest and Jasmine.
Table of Contents
🌩
Installation
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.
📝
API
Add Custom Matchers
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");
Add Custom Asymmetric Matchers
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")
});
➕
Writing Matchers
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.
Examples
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.
🙋🏽♂️ Getting Help
Get help with issues by creating a Bug Report or discuss ideas by opening a Feature Request.
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🤓
Author
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.
