The obvious mistakes you still make as a senior developer

Original post at: https://siderite.dev/blog/obvious-mistakes-as-senior-developer

I want to write this post to talk about the most common mistake I make as a software developer, even after almost 20 years of experience. And it's not code related. It's more human. But I would also like to hear what you think your biggest mistakes are that are not related to lack of experience. Don't be shy!

My mistake: assumptions.

I was assigned this bug recently and, wanting to do a fast job and impress people, I investigated the code, noticed a bug, fixed it, then immediately gave it in for review. I had reasons for doing that, because I was new and did not know the application well. The leads would tell me if they thought I did not find the problem. But, out of the goodness of my heart, you see, I've decided to test the fix as well. And I discovered that the feature was barely implemented. It was not a bug, it was a full fuck up.

What happened here? I assumed a certain quality of the code and expected, without any reasonable evidence, to find a small typo or a logic bug that would be solved by writing a few lines of code. Instead, I had to reimplement the whole thing as a fix, I pissed off the lead devs because they had enough on their plate and made the entire team wonder what I was doing there. I mean, I haven't even tested the fix!

Doing things fast means working on valid assumptions that allow you to cut corners. In a new environment, with a team you are not familiar with and a code base you don't understand, you do not have the luxury to make assumptions. Instead, do a good job first: investigate thoroughly, see what the reported problem is, find the actual problem (which may be different), come with an attack plan, implement it, then test that it had the desired result. Yes, it takes more time than to quickly compile the logic flow in your head and hope for the best, but in some places you don't get second chances at fixing things, teams are more formal, processes need to be followed. Optimism is also based on assumptions. Be a realist instead.

In order to win a game you need to know its rules. That applies both to development process and to local politics, which sometimes are more important than the work. Once you are a good player, you can start experimenting. The title "senior developer" is not given in a vacuum, but is relevant (or not) depending on the environment. Yes, you have experience, but you don't have *this* experience yet. In my desire to be efficient and fast I didn't do anything right and I couldn't believe I have been that stupid.

Now, how about you? What are your silly mistakes that you can't believe you are still making?