Boolean disjunction (OR) using mocha and chai

Question

I have the following scenario in which I have to check that an URL was build correctly provided some query arguments. I do not expect the system to apply an specific order in the rendered URL, so I came with the following test case which I expected to work:

it('test that url is built correctly', function () {
    var args = {
        arg1: 'value1',
        arg1: 'value2'
    };

    var rendered_url = render_url(args);

    expect(rendered_url).to.equal('/my/url?arg1=value1&arg2=value2')
                     .or.to.equal('/my/url?arg2=value2&arg1=value1')
    ;
});

I was pretty surprised to the or chain to not exists as it makes the statement construction process tidy and cozy.

I know I can workaround this in many ways (for example, using satisfy), but I wonder:

• Whether I cannot find the pattern to achieve in a similar way what I want in the documentation(I have read it thoroughly)...
• ... or whether there exists a good reason to not include this construction in chai...
• ... or whether there exists an alternative way to achieve a construction similar to the one in the example (tweaking, other frameworks, etc)

Answer 1

You could use to.include or .match:

var chai = require("chai");
var expect = chai.expect;

var option1 = '/my/url?arg1=value1&arg2=value2';
var option2 = '/my/url?arg2=value2&arg1=value1';

var possible = [option1, option2];

var re = /^\/my\/url\?arg1=value1&arg2=value2|\/my\/url\?arg2=value2&arg1=value1$/;

it('1', function () {
    var rendered_url = option1;
    expect(possible).to.include(rendered_url);
    expect(rendered_url).to.match(re);
});

it('2', function () {
    var rendered_url = option2;
    expect(possible).to.include(rendered_url);
    expect(rendered_url).to.match(re);
});

it('3', function () {
    var rendered_url = "foo";
    expect(possible).to.include(rendered_url);
});

it('4', function () {
    var rendered_url = "foo";
    expect(rendered_url).to.match(re);
});

The first 2 tests will pass, the last 2 will fail.

I've not done it in this example but both possible and re could be generated by a function rather than hand-coding all possible permutations of arguments.

I suspect the reason that .or is not in Chai is that it would complicate Chai's code quite a bit and make it more cumbersome to use for regular cases. Right now when .equal is called, it knows it is terminal. If Chai allowed to use .or, then .equal could not know right away whether it is terminal or not. Even if you had something like expect(foo).to.equal(bar), the call to equal cannot know that it is terminal. You'd have to do something like what some promises library do to signal that the code is finished with a promise and have a call saying "I'm done here" so it would look like expect(foo).to.equal(bar).end(). I'm not saying it would be impossible but it would have wide-ranging repercussions.

Answer 2

You could do something like:

expect(rendrered_url).to.satisfy(function(url){
    return url === '/my/url?arg1=value1&arg2=value2 || url === '/my/url?arg2=value2&arg1=value1';
});