By David Grieser

Is that feature done? Has that bug been fixed? These are the types of questions programmers get asked. Usually from a product manager that has a timeline and needs things done. This is their job. Yours is to provide the end result and know that what has been developed works! But sometimes you’re just not sure.

You may be fortunate to have a manager that pushes back for you to give you the time you need for development. If not, how do you manage these expectations? How do you go about gaining this confidence in yourself and the code? What can you do to bring about change? For now, focus on the small gains and what you have the most control over, the code you write.

Test Driven Development

One of the ways to gain confidence is to test your code. Often developers approach testing by placing debug statements in their code to make sure something works correctly. However, that is an ad hoc approach. It makes the code less readable, plus it doesn’t provide the reader (a future developer and maintainer of the code) any context!

You instead want to take a test driven development approach. You start by writing the test cases, along with the conditions that need to be satisfied to pass the tests, before you write your code.

The benefit to this approach is that you can repeatedly run that test to know your code still works the way you expect. The not so known advantage is that when a bug shows up 2-3 weeks later (or longer), when you look at that code, you’ll have a basis for how it functions and can fix it quickly.

Applying it to Legacy Systems

I suggest this style approach because I have taken it myself. Being tasked with adding a features to a legacy Classic ASP site, I knew making changes was going to be difficult. With very little structure and pages consisting of 1,000+ lines, introducing new code could cause things to break. Realizing this, I decided that a small library would be helpful; however, how would I write any tests?

To test this new library I happened upon a blog of someone who had done something similar. As to not repeat myself, I started with his code as a basis for testing.

The first tests were just to validate that a method call would produce a certain set of HTML tags.

Then I included some tests to handle both fetching and submitting data into the application’s database.

Once I had the pieces in place, I wrote some helper methods so inserting the code was as close to a single line as possible.

This code later went into production and I considered all was well. About a month later, the senior developer ping me and let me know there were 2 issues that had come up from the feature I had written.

After looking at the examples, I went straight to the tests. In both cases, I had not written a test for using this code in the way that was causing an issue in production. These tests were written (red) and then the functionality was implemented (green). I even got to refactor some of the duplication. All of this took only a few hours.

The final time there was an issue, I had it resolved in under an hour!

Taking a test driven development approach improves code quality and boosts your confidence as a coder. Plus it saves you time and make you a more productive developer.

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