In the previous posts we had a look at sinon spies and stubs. There is one more technique we can use in order to orchestrate our test dependencies: mocks.

In the previous post we had a look at sinon spies. With spies, we are able to determine if a specific function was called or not. Usually the dependencies between units are more interesting, they involve units co-operating, exchanging data and so on. Spies do not suffice. Let’s have a look at another technique, using stubs.

In the previous post, we implemented a new feature for our calculator: it makes a bell sound when you divide by zero. The bell is a simple function that the calculator calls and it is provided as a constructor dependency. We wrote a unit test for this as well, but the code for that is a bit verbose. Let’s see how we can use a mocking library like sinon to reduce and standardize the testing code.

We left our calculator in the previous post in a decent state, being able to do the four basic mathematical operations. In the special case of division by zero, we want the calculator to make a noise like a bell. Let’s see what we can do about this.

Last time we had a look at test driven development and our calculator learned how to do multiplication. In this post, we’ll add division and talk a bit about code coverage and unit test quality.

Let’s continue building up our calculator with more mathematic operations. So far we have addition and subtraction, so multiplication comes up next.  In this post, we’ll have a look at test driven development. Even though the examples are a bit trivial, I hope they’ll outline the important points.

In the previous post we started writing a basic Calculator class and added the first unit test. Let’s have a closer look at that unit test and extend our calculator with more features.

So, let’s start with some basics. What is a unit test? A unit test is a piece of code that validates the expected behavior of a unit in isolation. I guess the next question is, what is a unit? A unit is the smallest piece of code in a given programming language. Typically that is a function or a class method. Let’s see it with an example.

Unit tests is an essential method of ensuring quality and predictability of software. In my current work, we have been going through a hard learning curve involving many factors:

• developers not familiar with unit tests.
• a proprietary technology ecosystem where the community is typically not practicing unit tests at all.
• a legacy code base not written with unit tests in mind

Some time ago, I stumbled upon this article regarding productivity tools by ProductHunt. It’s a long list, but I noticed the first section “Habit and Goal Trackers”. The term habit tracker was new to me.