What is a good test?

A colleague asked that question the other day. What is a good test? It is a really difficult question to answer. There are a number of properties that hold true for a good test. I will list some of them and discuss why I think they are important. Others may think that the order of importance is different or that other properties are more important then those that I list.

I will show some examples using Java and JUnit of what I think are bad tests and how they can be refactored to something better.

Tests are automated in my world. I always try to avoid manually testing. The main reason for this is that manual testing is slow and hard to repeat arbitrary many times. Therefore, test should be read as automated test in for the rest of this text.

How many train wrecks are lurking in your code?

Train accidents are mostly considered to be bad things. People tend to get hurt when trains have accidents. Never the less, it is not so uncommon with train wrecks in software development.

Train wreck code is code that calls a method on the return value of another method call. This chain can be very long if a value is excavated deep down in a object graph.

The simplest possible solution

The simplest possible solution that could work. Ever heard that expression? What does it mean? Really?

The answer is obviously something that in a really simple way satisfies the test you currently are working on. Nothing more, nothing less.

Testing a web application with Selenium 2

Selenium a great tool for testing web applications. The current version, Selenium 2, is a merge between Selenium and WebDriver. I will walk you through an example where we test a web site using Selenium in a few different ways. This is the same example as I demonstrated at Scandev on tour in Stockholm 18 October 2011.

What is the difference between i++ and ++i?

During a coaching session I got a question about a loop.

Would there be any difference in the output from a loop defined as

for (int i = 0; i < 3; i++) {
    System.out.print(i + " ");
}

and a loop defined as

for (int i = 0; i < 3; ++i) {
    System.out.print(i + " ");
}

in Java?

Do not return null

Using your IDE to automatically create methods for you maybe a disaster waiting to happen.

Magic numbers

The other day a colleague asked me, what is a magic number? He had noticed that one of the things our Sonar was complaining about was Magic numbers. I got a great teaching moment and told him my view of Magic numbers.

Magic numbers are any numbers in the source code that just appears without any explanation.