By Chris Oldwood

Overload, 29(165):20, October 2021

It’s useful to step back and evaluate from time to time. Chris Oldwood reflects on reflection.

Way back in 2014, I gave a slightly extended lightning talk at the ACCU Conference titled ‘The Art of Code’ [Oldwood14]. One of the ‘humorous’ code snippets I presented lampooned the hidden complexity that can arise from the overuse of reflection based libraries and frameworks, most notably of the dependency injection kind. At the time, I had found myself face-to-face with a C# codebase that was difficult to reason about due to this very affliction and it also lead me to make the following pun on Twitter:

They say C# & Java developers have a habit of overusing reflection. Given the quality of their code, I’d say they’re not reflecting enough...

The vast majority of my Twitter puns are poor attempts at wordplay and throwaway comments, but every once in a while I realise there may be something deeper in the punchline that I wasn’t immediately aware of. Consequently, I now find myself reflecting on reflection, which feels awfully meta!

While I had never realised it until very recently, I believe my own interest in reflection is another one of those characteristics which I can attribute to Steve Maguire’s 90’s book Writing Solid Code. One of the ideas he introduces quite early on is the notion that when you find a bug, before fixing it, you ask yourself some questions, such as “How could I have prevented this?” and “How could I have automatically detected it?” The book goes on to introduce the use of ASSERTs to verify assumptions, along with cranking up optional compiler diagnostics and using static analysers to work smarter instead of harder.

Initially, I limited this practice to what the book was addressing – writing code – but as my experience as a programmer grew and I got to branch out into other disciplines, I found myself adopting the questions more and more whenever something went awry. Around the same time, Ed Nisley’s column in Dr Dobbs Journal began to explore some of the post mortems that NASA had been publishing and while I took solace in even their ability to fail spectacularly on occasion with the vast resources they had available, their desire to reflect and improve at every scale was an attitude I felt was laudable.

Consequently, that question grew from being a way to help avoid bugs in native code to being one that pervaded more and more aspects of both my professional and personal life. It wasn’t just limited to trying to help avoid my own mistakes either but became a more natural question to ask whenever something went wrong. I found I started developing a strong desire to avoid settling for simply fixing incidents in isolation and instead to see if there might be an underlying pattern and therefore find a way to avoid the entire class of incidents in future.

After many late nights in those early days of debugging native code, I was perfectly happy to buy into Maguire’s advice around leveraging tooling and practices that would minimise these problems. It didn’t take me long to be sold on unit testing and then Test Driven Development (TDD) once I became aware of them and my own inadequacies at manual testing. (Interestingly, Maguire only makes a passing comment about unit tests: if you have them, you should run them. I now wonder what unit tests looked like back in the early ’90s!)

In a metaphorical sense, you might consider a test-first mentality to be the ‘reflection’ in a timeline from a post-debugging retrospective – a desire to unearth defects as early as possible is a natural consequence of frustration after being by bitten by a problem that could have easily been avoided. Even if the problem was unavoidable, being in a position to automatically validate and deploy the resulting fix quickly is still a much better place to be than facing another phase of handovers and manual testing.

That level of pessimism which comes with hard won experience was once summed up wonderfully by @fioroco on Twitter in 2017 [Fioroco17]:

junior dev: “i found the bug”
senior dev: “i found a bug”

Naturally, there is a balance here. Sometimes it is just a simple mistake but other times it’s a more fundamental misunderstanding. I once discovered a memory leak caused by a non-virtual destructor in a base class. Rather than fix it and move on, I checked for a pattern and quickly found the same author had done it another 19 times and, although not in my team any more, was still only a few desks away. They really appreciated the heads up and I managed to stem the tide in two systems.

On the interviewing front, I’ve begun to feel that a tendency to reflect on one’s work is probably a strong indicator of quality, even if they haven’t performed it as a formal exercise like a retrospective. I’ve never really been one to ask classic interview questions like “What does SOLID stand for?” but I wanted candidates to try and embellish more on the ‘why’ when talking about what they’ve worked on – I like decisions to be conscious rather than done by rote. Hence if a candidate lists something like SOLID on their CV, I’d ask them “Give me an example of a time when you applied one of the SOLID principles as part of a refactoring.” I’ve found this style of question provides more avenues to explore their thought processes and understanding of a topic.

Even if behaviours are apparently done by rote now, maybe they were once done more consciously and it’s been a while since any reflection was performed on the practice or the conditions under which it once applied. It’s taken a beating over the last few years due to misuse in some circles but the principle of ‘strong opinions, weakly held’ is still one I feel is valuable. The school of hard knocks can send us down a more cautious path which often bears fruit for a considerable time, but we should be open to being challenged and accept that progress may have been made in the intervening years. I now find that usually comes from others, but not as direct criticism, more as a fleeting comment which I once might have simply dismissed but now embrace as an opportunity to re-evaluate past decisions.

Maguire’s book also taught me to “step through your code [with a debugger]” – a practice which I found invaluable for so many years. Even after adopting unit testing and then TDD, I struggled to let go of the debugger even when writing tests. But what caused me to drop it in the end wasn’t more confidence in my ability to solve problems correctly first time but that the massively reduced cost of failure and recovery in modern software development meant that I could be far less paranoid of the consequences.


[Fioroco17] Tweet posted 4 Dec 2017, available at

[Oldwood14] Chris Oldwood (2014) ‘The Art of Code’, ACCU Conference 2014, available at

Chris Oldwood is a freelance programmer who started out as a bedroom coder in the 80s writing assembler on 8-bit micros. These days it’s enterprise grade technology plush corporate offices the comfort of his breakfast bar. He has resumed commentating on the Godmanchester duck race but continues to be easily distracted by messages.

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