Comments are deodorant for your code

Writing comments in a program is often considered a good habit. I hear people talking about code as "good and well commented". This always makes me skeptic. What do people mean with "well commented"? It turns out, they often mean that every method has a lot of comments.

Gradle and Cucumber-JVM

Gradle is a great build tool. Cucumber-JVM is a great tool for executing Gherkin. They don't really work well together. At least not out of the box. Gradle defaults to hide the output on stdout and stderr. This is very unfortunate since this means that the code snippets Cucumber-JVM suggests when there is a missing step are hidden.

Let me show you an example on how to setup a Gradle project so it can execute Cucumber-JVM and give you the snippets you want as starting points for your steps.

Expected exceptions

Sometimes you want to verify that an exception is thrown in your code.

Let me show you three different ways to verify that the expected exception has been thrown.

Packaging a zip file from Java using Apache Commons compress

How do you create a zip file with Java? One option is to use Apache Commons Compress.

This example shows you how.

Tell, don’t ask

Objects that expose wrong information are complicated to work with. They force you to dig for the information you really need. It is easy to create a model where the users are expected to know a lot about the domain and therefore force them to dig deep into an object structure to get the information they currently need. This can be avoided if you strive for telling objects what to do and only ask them occasionally.

Separating acceptance tests

It is very convenient to run the unit tests separated from other, slower, tests. There are different ways to do this. One way is to have a separate module for the acceptance tests.

Separating the modules is acceptable in some cases. It is not acceptable in others. There is a simple way to separate the source code for the acceptance tests while keeping the it in the same project if you use Gradle. Separate the tests with different source sets.

Separation on source sets means that you will keep all the acceptance tests in another directory structure than the unit tests. If you use the usual separation of production code and test code, then all you want to do is to add a new source set that contains the acceptance tests.

Stubbing a var arg method using Mockito

I had a need to stub a method the other day that had a var arg method. I failed in stubbing it using Mockito. It disturb me a lot. But after mulling on the problem a while, I searched and found a simple solution.

Mockito has a anyVararg() method that you should use when you try to stub a method that takes a var arg as argument.

A Gradle plugin written in Java

Gradle is a build automation system. You write your build script in Groovy. This is different compared to other build system such as Ant or Maven. They both use xml. Using Groovy instead of xml gives you a lot of benefits. You have an entire programming language at your disposal. This mean that you can easily customize the build behaviour.

If you, however, want to be able to do the same thing in many projects, it may be a good idea to write a plugin that you can refer to from other projects. I will show you, step by step, how to implement a Hello World Gradle plugin.

Hard code first

I came across this tweet the other day:

"Novice engineers have not yet grokked this: the number of modes or options in your system is the *exponent* in how hard it is to maintain." by @zooko.

This is very true. The more options a system has, the harder it is to understand, maintain and use. This is one of the reasons why I usually always try to hard code things like parameters to scripts in my first iteration.

Hard coding is something that some of my colleagues sometimes have a hard time to accept. It happens that the argument is "I don't like hardcoded things". I can understand that point of view and I extract parameters when I have got one use case working with a hard coded solution. But I don't do it before I have something working.

Cucumber data tables

Cucumber has a nice feature that will help you to use tables in your scenarios. The table can easily be converted to a list or a map that you can use in your step. I will show you a few examples that may help you get started.

Test drive an implementation using an Executable Specification

An example is perhaps the best way to describe something. Concrete examples are easier to understand then abstract descriptions.

I will show how Cucumber-JVM can be used to specify an example and how the example can be connected to the system under test, SUT. The example can then be executed using any IDE or using Maven.

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?