WhenIt / ThenIt syntax for JS unit tests.

Works with Mocha or Jasmine test frameworks.

The intent is to provide a way to make small reusable functions that are used between several tests, without having to duplicate code between tests. It also provides a way to move test names from plain strings into function names.

Installation

Get the files.

npm install when-it --save-dev

Add to your test environment.

require('when-it');

// or with a regular script tag

<script src="node_modules/test-when-it/index.js" type="text/javascript"></script>

Use

setIt(propertyName, propertyValue)

This function assignes a property getter with the name propertyName to the this context. The property is deleted after each test.

The propertyValue parameter can be a literal value, or a function. If a function is passed, it is called each time the property is accessed and the return value is used as the property value (like a property getter). (The value is not memoized like Ruby/rspec's let())

describe('using setIt', function() {
	setIt('fromLiteral', 'valueFromLiteral');

	setIt('fromFunc', function() {
		return 'valueFromFunc';
	});

	it('makes a value available on the test context', function() {
		expect(this.fromLiteral).to.equal('valueFromLiteral');
	});

	it('makes the return value of a function available on the test context', function() {
		expect(this.fromFunc).to.equal('valueFromFunc');
	});

});

whenIt(..)

The whenIt(...) function takes any number of arguments that act as test setup (aka beforeEach). The last parameter must be a function that is executed as the test context.

The following things can be passed to the whenIt function:

• Function - The function will be executed as a beforeEach step. If the function has a .name then the name will be appended to the test name. If the function returns another function, then that returned function will be called in an afterEach step. Example:

describe('example', function() {
	function setsUserToBob() {
		this.user = 'Bob';

		return function() {
			delete this.user;
		}
	}

	whenIt(setsUserToBob, function() {
		it('can access the user name', function() {
			expect(this.user).to.equal('Bob');
		});
	});
});

// The above code is equivelant to this "normal" mocha test code:

describe('example', function() {
	describe('when it sets user to bob ', function() {
		beforeEach(function() {
			this.user = 'Bob';
		});

		afterEach(function() {
			delete this.user;
		});

		it('then it can access the user name', function() {
			expect(this.user).to.equal('Bob');
		});
	});
});

• String - The string will be appended to the test name.

• Object - The properties of the object will be copied to the this test context during the beforeEach step. The properties will then be deleted from the this context in the afterEach. Example:

describe('example', function() {
	whenIt('sets user to bob', { user: 'Bob' }, function() {
		it('can access the user name', function() {
			expect(this.user).to.equal('Bob');
		});
	});
});

• Fixture - See further information below.

thenIt(..)

The thenIt function can be passed multiple functions. Each function is executed as its own it() test. Example:

describe('example', function() {
	function setsTheUserToAString() {
		expect(this.user).to.be.instanceOf(String);
	}

	function setsTheUserToBob() {
		expect(this.user).to.equal('Bob');
	}

	whenIt('sets user to bob', { user: 'Bob' }, function() {
		thenIt(setsTheUserToAString, setsTheUserToBob);
	});
});

// The above code is equivelant to this "normal" mocha test code:

describe('example', function() {
	describe('when it sets user to Bob', function() {
		beforeEach(function() {
			this.user = 'Bob';	
		});

		afterEach(function() {
			delete this.user;
		});

		it('sets the user to a string', function() {
			expect(this.user).to.be.instanceOf(String);
		});

		it('sets the user to Bob', function() {
			expect(this.user).to.equal('Bob');
		});
	});
});

new Fixture(...)

An instance of the Fixture object can be passed to whenIt and it used to encapsulate a name and test before/after steps.

The constructor must be passed an object of the form:

var doesSomething = new Fixture({
	name: 'a string name to insert into the test name', // required.
	before: function() {}, // run during beforeEach. optional.
	after: function() {} // run during afterEach. optional.
});

whenIt(doesSomething, function() {
	it(...);
});

The instance also exposes a .apply() function. You can pass any arguments to the function, and those arguments will be passed to the before and after functions.

var setsUser = new Fixture({
	name: 'sets the user',
	before: function(name) { this.user = name; },
	after: function(name) { delete this.user; }
});

whenIt(setsUser.apply('Bob'), 'to Bob', function() {

	// full test name is "when it sets the user to Bob the user is set to Bob"
	it('the user is set to Bob', function() {
		expect(this.user).to.equal('Bob');
	});
});