js-janus

Looking for a no-nonsense testing framework for JavaScript? This is probably what you came for. Or not. Named after Janus - the ancient Roman gatekeeper - Janus.js is here to keep wrong code from entering your codebase.

Usage

Usage is fairly simple. Let's first setup an add() function.

const add = (...nums) => nums.reduce((total, n) => total + n);

To test this function, first set the description of the test case.

test('1+1 equals 2');

Specify the unit test and inject tools that the test needs.

test('1+1 should be 2', ({ expect }) => {
	expect(add(1, 1)).toBe(2);
});

A full list of tools is described below.

Advanced usage

This test framework also has some extras that may be useful. Your unit test can use destructuring assignments to receive tools and dependencies needed to complete the test.

Expectations

The most important function to inject into your test is expect. This function allows you to make assertions on your code.

test('Expectations', ({ expect }) => {
	const a = 100;
	expect(a).toBe(100);
});

Supported comparators are below.

.toBe()

This comparator does a strict equality check (===) when comparing the expected and actual result.

.toEqual()

This comparator performs a deep equality check. Expected and actual values may not be the same object, but if their values are the same, this comparator returns true.

.toHaveBeenCalled()

This comparator is used with observed functions. If an observed function is called, this comparator returns true.

.toHaveBeenCalledTimes()

This comparator is used with observed functions. Specify the amount of times you expected the observed function to have been called.

.toHaveBeenCalledWith()

This comparator is used with observed functions. Use it to determine if an observed function is called with specific parameters.

Observations

Inject observe into your test to observe function calls. The syntax is similar to Jasmine's spyOn.

test('Observed functions', ({ expect, observe }) => {
	const obj = {
		fn() {}
	};

	observe(obj, 'fn');
	obj.fn();

	expect(obj.fn).toHaveBeenCalled();
});

By default, the observed function is called as usual if any tests invoke it. To prevent that, simply pass false as the third argument to observe().

observe(obj, 'fn', false);