Styles

Assert style

Not a big fan but it's nice for the occasional use, only two primitives are exposed in this style: ass.ok and ass.ko. The former succeeds if the value is truthy (value == true in Javascript), the later is the inverse.

They come with a nice twist, they will perform the assertions and return the exact same value that was provided. This allows to use them to validate some values while actually using them.

var data = {option: true};

ass.ok(data)

var x = ass.ok(data).option

Expect style

Just wrap any value you want to be the subject of the expression with ass() and start chaining matchers to it.

ass('foo').string                     // not impressed right?
ass('foo').string.size.eq(3)          // ok, the chain can mutate the subject!
ass('foo').size.eq(3).value === 'foo' // oh boy! the original value is back!

As we've seen in the above example it's possible to chain the expectations at will, some of them do not actually test anything, they just mutate the subject for the remaining of the expression. At any point we can get back the original value by using .value or .valueOf().

Should style

It just looks nice to have you assertion subject on the left without anything else cluttering its view. You can use should style expressions easily and they behave the same as the expect style ones.

// Install .should on Object.prototype and assign the static interface to the
// `ass` variable. Additionally by passing a custom name it'll be used as
// property name instead of `should`.
var ass = require('ass').should();  // NOTE: the function must be called!

"foo".should.be.a.string;
[1,2,3].should.contain(2);

// We can't use .should directly if the value is null or undefined
ass(obj).should.be.null;

// Unregister should from Object.prototype
ass.should.restore();

beforeEach(ass.should);
afterEach(ass.should.restore);