Using sinon spies

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. Continue reading Using sinon spies

The division by zero bell – Dependencies in unit tests

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. Continue reading The division by zero bell – Dependencies in unit tests

What is Test Driven Development?

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. Continue reading What is Test Driven Development?

What is a unit test and why should I care?

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.

Continue reading What is a unit test and why should I care?

When developers cannot unit test

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

Continue reading When developers cannot unit test

On the left-pad drama

This week the internet exploded in drama after 11 lines of code got unpublished from npm. If you didn’t read about it, the summary is that the developer of left-pad removed his package from npm, after npm renamed another package of his because of some name conflict with some other company’s trademark or so. Lots of other packages broke because of this due to the missing dependency. What is interesting here, is that this removed left-pad package consists of a single function (only 11 lines of code). How can that tiny package break the internet? Continue reading On the left-pad drama

Code coverage for open source .NET with AppVeyor and Coveralls

Code coverage is a useful metric of the quality of your code. It shows how much code is being covered by unit tests. It doesn’t necessarily mean that the unit tests are well written, but no metric can probably tell you that. However, aiming for a specific code coverage, let’s say 70%, is a good practice, because failing to meet the goal might mean somebody didn’t write enough unit tests.

I’d like to have code coverage as part of the CI I had set up in a previous post with Travis. The bad news is that code coverage and Mono seem to be strangers. There is an open source module called monocov but I couldn’t get it to work. In fact in the homepage it says it’s not maintained. In my opinion, these kind of tools are essential and they should be included in the core Mono package. I hope they change this some day. Continue reading Code coverage for open source .NET with AppVeyor and Coveralls