Testo

A small testing utility based on the Writer monad.

npm i @opeltre/testo

Tracer Monad

The Tracer monad logs strings alongside Maybe values.

//  Tracer a = Writer (Maybe a)

//  ta : Tracer Int
let ta = [1, ['all', 'good']]

//  tb : Tracer Int 
let tb = [null, ['oops', 'no int!']]

All tests return values inside the Tracer monad, e.g.

//  unit : () -> Tracer Bool 
let unit = () => {
    let expect = 1, 
        obtain = someIntFunction(); 
    return expect === obtain 
        ? [true, ['1 = 1']],
        : [false, [`1 != ${obtain}`]];
}

Running tests

Each testing file exports a collection of unit tests, which are functions to the Tracer monad.

    File = {Unit} 
    Unit = () -> Tracer a

Units are run one by one by providing test.run the files to be tested, e.g.

//  tests.js
let test = require('@opeltre/testo');

let a = require('./fileA.js'),
    b = require('./fileB.js');

test.run({a, b}); 

Running $ node tests.js will then log all encountered errors if any, and provide some feedback.

Writing unit tests

The main test object exports comparison functions to conveniently write these tests.

//  fileA.js
let test = require('@opeltre/testo');

//     .t1 : () -> Tracer ()
exports.t1 = () => {
    let expect = [0, 1, 2],
        obtain = [0, 1, 3]; 
    return test(expect, obtain);
}

//     .t2 : () -> Tracer ()
exports.t2 = () => 
    let expect = {a: [0, 1]},
        obtain = {a: [0, 1], b: [1, 2]};
    return test(expect, obtain); 
}

Using with npm

Edit your package.json to:

... "test": "node tests.js"

And run $ npm test