Most interesting links of December

Recommended Readings

• The Netflix Chaos Monkey – how to test your preparedness for dealing with a system failure so that you won’t experience nasty wakeup when something really fails in Sunday 3 am? Release a wild, armed monkey into your datacenter. Watch carefuly what happens as it randoly kills your instances. This is exactly what Netflix does with their with their cloud infrastructure – also a great inspiration for my recent project. Do you need to be always available? Than consider employing the chaos monkey – or a whole army of monkeys!
  (PS: There is also a post with a picture of the scary monky.)

Links to Keep

• BDD: Write specifications, not scripts (from the Concordion site) – relatively brief yet very enriching practical description of how to do behavior-driven development a.k.a. Specification by Example right, the key point here being “Write specifications, not scripts.” It says why not (for scripts overspecify -> are brittle, specs should be stable) and how to do it (decouple the stable spec and the volatile system via fixture code, expose minimal stuff to the spec, perhaps evolve a DSL between the fixture and the system). It also lists common “smells” of BDD done wrong. If it still isn’t clear to you, read the Script to Specification Makeover example (or perhaps read it anyway). BTW, Concordion is a new tool for doing BDD based on JUnit and HTML, which was created as a response to the weaknesses of Fit[Nesse], i.e. exactly the tendency to do scripting instead of specifications. It looks very promissing to me!

SW Utilities

• (Linux/Mac) Autojump – superfast navigation between favorite directories in the command line (via Jake McCrary) – it keeps track of how much time you spend in each directory and when you execute j <substring of directory path/name>, it jumps into the most frequently used one matching the substring. It awesome! (You can also run jumpstat to see the statistics.)
• (Linux) Tcpkill – service/network outage testing (via Jake McCrary) – kill connections to or from a particular host, network, port, or combination of all – useful e.g. when you want to test that your software is resilient to the outage of a particular service or server – less brutal than actually killing the database etc. instances. We need to test that our application recoveres properly when one of our MongoDB nodes dies so this may be quite useful.
• Manik Hot Deploy Plugin for Maven Projects (v1.0.2 in 5/2011; older version in the Marketplace) – plugin that can do hot and incremental deployment to any app server (simply by copying to its hotdeploy directory or the directory of an installed webapp) whenever you run mvn install or automatically whenever sources change, multi-module support

Clojure Corner

• Jake McCrary: Continuous Testing With Clojure and Expectations – continuous test runner lein-autoexpect for Clojure tests written using the library expectations by Jay Field.
• Jake McCrary: Quickly Starting a Powerful Clojure REPL – Clojure REPL only two steps away: 1) Run Emacs, 2) Execute M-x clojure-swank (no more need to open an existing Leinigen project) – the trick is to install the Leinigen plugin swank-clojure and use Jake’s elisp function clojure-swank that automatically starts the swank-clojure server. (I had to hack the function for the clojure-swank output contained “null” instead of “localhost”, likely due to incorrect DNS setup.)

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Most interesting links of May

Recommanded Readings

Acceptance testing / Specification by example:

• Gojko Adzic: Anatomy of a good acceptance test – an example of refactoring a bad acceptance test into a good one – good for learning about pitfalls and how a good one should look like
• Gojko: Top 10 reasons why teams fail with Acceptance Testing – acceptance testing is great and brings lot of value but must not be underestimated; some of the problems are bad collaboration, focusing on “how” instead of “what,” confusing AT with full regression tests. Brief, worth reading.
• Specification by Example: a love story (go directly to the PDF with the story): A nice, made-up story of going from low-level, workflow-based Selenium tests through similar Cucumber ones to true BDD tests describidng clearly what, not how – very well shows the point of specification by example and how it should (and should not) look like

(Enterprise) Java best practices:

•  Clean code, clean logs: 10 brief posts on logging best-practices – nothing really new here for me but in total it is a very good overview that every developer should know
• Make Large Scale Changes Incrementally with Branch By Abstraction – Continuous integration doesn’t work well with branches but as this article shows, you can manage even large-scale refactorings without branches using “branch by abstraction,” an approach reminding me of Fowler’s “strangler application” (an incremental replacement of a legacy system). The idea is: 1. Create an abstraction over the part of code to be changed;  2. Refactor the code to use it; 3. Implement new functionality using the new way / step by step move old functionality too, the abstraction layer delegating either to the new or old implementation … . It may be more work but: 1) your software is always working and deliverable; 2) (side-effect) in the end it will be more decoupled

Git:

• John Wiegley’s Git from the bottom upp (31p, Git 1.5.4.5, PDF) – a useful explanation of the fundamentals of Git, i.e. how it is constructed and how it works, which makes it much easier to understand how to  use it properly (recommended by Pål R.). Reading the The Git Parable first may be a good idea for an easy introduction into the fundamentals, though absolutely not necessary. This document introduces very well the important Git concepts (blob, index, commit, commit names such as branches, reflog) and how they cooperate to provide the rich set of functionality it has. It also explains well the value and usage of rebase. Among others I’ve appreciated the tip to use checkout, branch -m <new-branch> master, branch -D instead of the much more dangerous reset –hard and the tip to use stash / stash apply to create daily backups of your working tree in the reflog (with clearing it with ‘git reflog expire –expire=30.days refs/stash‘ instead of stash clear). Also git diff/log master..[HEAD] for reviewing work done in the current branch and and git diff/log ..master for checking the changes since the last merge/rebase after a fetch are interesting.

Tools:

• The secret power of bookmarklets – bookmarklets are an indispensable tool for every developer who works with web applications (to fill in test data, speed up log in, …), yet I’m sometimes surprised by meeting people who don’t know or use them; this blog explains them nicely, links to some useful ones and some useful tools for building them

Recommended Books

• (*****) Implementing Lean Software Development: From Concept to Cash by Mary Poppendieck, Tom Poppendieck – A great introduction into lean thinking (the values and principles it is build upon), clearly communicated with the help of “war stories”. I absolutely recommend it to anybody interested in lean/agile.
• (**** ) Agile Project Management with Scrum (Microsoft Professional) by Ken Schwaber – Even though you can’t understand Scrum without experiencing it, this book full of war stories will help you to avoid many Scrum implementation pitfalls and to understand its mantra of “the art of the possible” and will show you how to adapt Scrum to various situations. It’s very easy to read thanks to its format of brief case studies organized by topics (team, product owner, …).

Favourite Quotes of the Month

@unclebobmartin: Cleaning code does NOT take time. NOT cleaning code does take time.