Test Doubles ~ How do jasmine/jest/mocha/chai and sinon stack-up

In the real world, jargon is sometimes confusing to the point some words may lose their intended meaning to some audiences. This blog re-injects clarity on some misconceptions around testing jargon.

In this article we will talk about:

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Show me the code

	.exec(function(err, order){ 
        /** ... */

new Order(params).save((error, order, next) => {
    if(error) return next(error, null);
    new OrderService(order).scheduleShipping();
    return next(null, order);

Example: Used to showcase test double usage

Asking the right questions

When trying to figure out the “what does what” with testing stacks, the following questions gives a clue on how to differentiate one concept from the next and one tool from the next:

This article is unfinished business and will be adding more content as I gather more confusing terms, or find some more interesting use cases.

In the test double universe, there is a clear distinction between a stub, a fake, a mock, and a spy. The stub is a drop-in replacement of a function or method we are not willing to run when testing a code block. A Mock, on the other hand, is a drop-in replacement of an object, most of the time used when data encapsulated in an object is expensive to get. The object can either be just data, or instance of a class, or both. A spy tells us when a function has been called, without necessarily replacing a function. A fake and a stub are pretty close relatives, and both replace function implementations.


In this blog, we explored differentiations around test strategies and testing tools. Without prescribing a solution, we let our thoughts play with possibilities around solutions and strategies that we can adapt for various use cases and projects.


#snippets #code #annotations #question #discuss