What is a Scratchpad?
When you have a question like “what exception is thrown when I try to convert a long that is too big to an integer” or “what is the difference in performance between iterating over a list or a dictionary converted to a list” what do you do? Google it? Phone a friend? Open up an instance of your IDE and give it a try? I think that sooner or later, most developers ‘graduate’ to the latter, particularly for things that can’t be answered with a quick search or question of a coworker. And, if they wind up doing this enough times, they start creating a project or project(s) with titles like “dummy”, “scratchpad”, “throwaway”, “junk”, etc — you get the idea.
As this practice grows and flourishes, it starts to replace google searches and ask a coworker to a degree, even when those things might be quicker. If you get very used to setting up experiments in this fashion, it tends to be almost as quick as a search, and there’s less potential for wrong or misleading information. This is a very useful practice but, more interestingly for the purposes of this post, I think the makeup of this scratchpad (I’m using this term because it’s what I name mine) can tell you a lot about the developer using it. In fact, I believe strongly enough in this that I see a lot of value in the interview question “tell me about your scratchpad and how you use it.”
I’ll say in advance that I’m going to paint with some broad strokes here. So, please read the following while bearing in mind the caveat that there will, of course, be exceptions to the ‘rules’ that I’m describing. In the examples below that describe a single type of scratchpad, please note that I’m referring to situations where this is the primary or only scratchpad that the developer uses. I’ll describe the “arsenal” of scratchpads further down.
If someone doesn’t have something like this, they’re quite likely either not very seasoned as a developer or else not very inquisitive when it comes to understanding their craft. The lack of such a playpen project implies that they either don’t experiment or that they experiment in production code, which is pretty low rent and sloppy. (One possible exception is that they experiment in a project’s unit tests, which is actually a pretty reasonable thing to do, and an example of a reason for my “broad strokes” caveat). In either case, they’re lacking a place that they can go in and just throw some code around to see what happens.
Extrapolating out to the way a person with no scratchpad works, it seems very likely that you will observe a lot of “debugger driven development” and “programming by coincidence”. The reason I say this is that this person’s natural reaction to a lack of understanding of some facet of code will most likely be to try it in the production code, fire up the application, and hope it works. I mean, lacking a playpen and tests, what else can you really do? It’s all well and good to ask a coworker or read something on stack overflow, but at some point an implementation has to happen, and when it does, it’s going to be in the production code and it’s probably going to be copy-pasted in as a matter of faith.
I’d be leery of a programmer with no scratchpad. It might be lack of experience, lack of curiosity, or lack of interest, but I’d view this as most likely a lack of something.
This is a scratchpad project that has the kitchen sink, from persistence on up to the GUI. In shops/groups that make a single product, it may be as simple as a duplicate of that project. In shops with more projects, it may be one of them or a composite of them. But, whatever it is, it’s a full fledged application.
Extra points here for being clever enough to have a consequence-free, dummy environment and for recognizing the value of experimentation. This is usually a sign of an inquisitive developer who wants to take things apart and poke at them, or at least a conscientious one who wants to try things out in dress-rehearsal before going live. I’d take some points away, however, for the monolithic approach here, assuming that this is the primary scratchpad and not an auxiliary or temporary approach. The reason I’m not such a fan of this is that it’s indicative of someone who hasn’t yet learned to think of an application in seams, components, modules, units, etc.
I mean, think about how this goes. “I wonder what happens if I use a string array instead of a string list here” leads to trying out the change and then firing up an entire application, complete with GUI bells and whistles, database access, file reads/writes, loggers, etc. This represents a view of the software that essentially says “it’s all or nothing, baby — here we go.” Good on them for the experimentation, but we can certainly do better.
Console Based Scratchpad
The console scratchpad (and this is a little Visual Studio specific, though it’s applicable to other IDE/environments as well) is one in which the main running application is one that writes to and reads from the console. If you wanted to time stuff you’d be doing so using a lot of System.out.println() or Console.WriteLine() or whatever the equivalent in your choice of language.
This correlates with the good characteristics of the GUI/application scratchpad (curiosity, judiciousness) but adds a bit more sophistication. A developer with a console based scratchpad understands how to decompose and abstract concepts and how to isolate problems. I think that this is potentially indicative of a competent and potentially great developer perhaps ready for a push.
Class Library Scratchpad
The most sophisticated scratchpad, in my mind, is the class library scratchpad. This is a scratchpad that has no program output of any sort and cannot be run independently. What this means is that the developer is used to reasoning about units and experimenting in very small, isolated fast feedback loops. Someone doing things this way clearly understands that increasingly complex applications are assembled from solutions to manageable problems rather than with some kind of irreducibly complex, inter-connected gestalt. Someone with this style of scratchpad is almost certainly a unit tester and most likely a practitioner of TDD (I certainly recognize my own bias here). But the most important thing here is the ultra fast and simple feedback loop, where answers to “how does this work” are provided right in the IDE itself (and extra points for anyone running a continuous integration tool like NCrunch.
A monolithic scratchpad is one that tends to be a developer’s only scratchpad. I think that this tends to be indicative of an architecturally minded developer capable of thinking in significant abstractions. The monolithic scratchpad is one that encompasses all of the projects above in one. It has test projects for fast feedback. It has a persistence model or two and a domain of sorts. It has a web front end and a desktop front end and mobile front end. In short, the developer organically evolves this scratchpad to suit whatever experimentation needs arise, demonstrating an ability to grow an application in response to whatever needs arise. Someone with this sort of scratchpad setup is someone I’d keep my eye on as a potential architect.
Arsenal of Scratchpads
An arsenal of scratchpads is indicative of a developer seasoned enough to understand that different questions call for different environments, but someone more silo-oriented and, perhaps, very well organized in a sense. While it may not occur to this person to blend scratchpad needs into an ad-hoc, decently architected application, the work nevertheless exists in such a way that it’s easy to find, access, and use. Since the response to new situations is new scratchpads, the critical fast feedback loop is there since they never get very big. I think that this practice is indicative of someone who might excel in small to medium sized picture development work or, who might do well on the path to project management. A monolith scratchpadder and an arsenal scratchpadder could probably form a pretty good leadership tandem on a project.
What Does your Scratchpad Look Like?
I’d like to reemphasize that this is a fairly lighthearted post that I fully acknowledge may completely miss the mark in categorizing some people. But, I do think there’s a grain of truth to it, and I stand by my assertion that this would make for an excellent interview question. If you have one of these types of scratchpads and either reinforce or poke holes in my premise, please weigh in. Same if you have a scratchpad setup I hadn’t thought of.