This handy tool can be used to implement additional logic into your assertions, either using Chai, Jest, Assert, or plain JavaScript.
Install the package:
npm install assert-logic --save-dev
Use it in your tests:
const {and, or} = require('assert-logic');
const {expect} = require('chai');
test("Test if a number is even and greater than 10 or less than 7", () => {
const number = 12;
and(
() => expect(number).to.be.an('number'),
() => expect(number % 2).to.equal(0),
or(
() => expect(number).to.be.lessThan(7),
() => expect(number).to.be.greaterThan(10),
),
).evaluate();
});
In the context of this package, a value is considered failed if it is:
undefined
)undefined
)undefined
)undefined
)In all other cases, the value is considered passed.
The API contains the following functions: and
, or
, not
, xor
, nand
, nor
, xnor
, every
, some
, and also the evaluate
function.
The following ones accept any number of sync/async functions, Promises, or values as arguments.
Operation | Description |
---|---|
and | Passes if all of its arguments pass |
or | Passes if any of its arguments pass |
not | Negates the result of its argument |
xor | Passes if odd number of its arguments passes |
nand | Passes if any of its arguments fails |
nor | Passes if all of its arguments fail |
xnor | Passes if all of its arguments pass or all of them fail |
The every
and some
functions are used to evaluate an array of values. The values must be the first parameter, but both functions accept a second parameter that is a function that will be called with each value. If the function is not passed as the second parameter, the value will be interpreted as boolean values.
The every
function is a shorthand for and
with the values as arguments, while the some
function is a shorthand for or
with the values as arguments.
const {every, some} = require('assert-logic');
const {expect} = require('expect');
const items = [{id: 1, name: 'Item 1', price: 10}, {id: 2, name: 'Item 2', price: -20}, /* ... */];
every(items, item => {
expect(item.id, "Item should have ID as positive number").toBeGreaterThan(0);
}).evaluate(); // will not throw
some(items, item => {
expect(item.price, "Item should have a positive price").toBeGreaterThan(0);
}).evaluate(); // will throw
The append
function can be used to append additional logic to an existing variadic logic (all except pass
).
const {and} = require('assert-logic');
const logic = and(
() => true,
() => false,
);
logic.append(() => true).evaluate(); // will throw an error
The evaluate
function will evaluate the logic and throw an error if it fails.
The evaluate
function does not need to be called if the logic is used as an argument to an assertion, as the assertion
will call it automatically.
The evaluate function will return a Promise if any of the arguments are async.
Given the following expression what is expected to fail:
and(
xor(true, false, true),
true,
).evaluate()
The error message will look like this:
AssertionError (AND): Expected all expression to pass, but not all did.
Results:
- AssertionError (XOR): Expected odd number of expressions to pass, but even number did.
Results:
- Pass
- AssertionError (PASS): Expected expression to pass.
Results:
- Error: "Failed expression: (boolean false)"
Expression: (boolean false)
- Pass
Expression: |-
XOR(
(boolean true)
(boolean false)
(boolean true)
)
- Pass
Expression: |-
AND(
XOR(
(boolean true)
(boolean false)
(boolean true)
)
(boolean true)
)
This package is not meant to be used as a replacement for assertions, but rather as a tool to implement additional logic into your assertions.
const {and} = require('assert-logic');
const {expect} = require('chai');
test("Test if a number is even and greater than 10 or less than 7", () => {
const number = 12;
and(
expect(number).to.be.an('number'),
expect(number % 2).to.equal(0),
or(
expect(number).to.be.lessThan(7),
expect(number).to.be.greaterThan(10),
),
).evaluate();
});
This will not work as expected, as the assertions will be evaluated before the logic is evaluated.
For detailed documentation see the TypeDocs documentation.
This package uses debug for logging, use assert-logic
to see debug logs:
DEBUG=assert-logic node my-script.js
Generated using TypeDoc