Fear Driven Development and How To Tackle It

On the internet there are a few different perspectives on Fear Driven Development (FDD). The perspective I want to focus on here is below:

The impact of fear on decision making whilst one is making software changes to a system.

Close your eyes and imagine someone looking at some code on a computer screen, they need to make a change to that code. They then do something you would not expect, and you want to ask them why they chose to make that decision (you can't because they are in your imagination). This decision was not driven by rational thinking, it was driven by something far worse. That is where we will focus our attention in this article. The code.

1. Where the fear starts

FDD is alluded to in the C2 wiki as "maintaining the code is hard because you don't know what unintended effects your changes have" in reference to what is known as "legacy code". Let's start there and define what legacy code is:

Code that you are afraid to change

Nice and simple right? That definition is simple, and deliberately so. The focus of this post is not to define what legacy code is.

In another post by Scott Hanselman, there are descriptions of FDD pertaining to organisational fear and the fear of losing your job. However, we will focus our attention on the small section at the bottom about changing code.

So where does this fear start? Well, it could be some of the following:

  • unfamiliar with codebase
  • new to the team (and don't want to screw this up)
  • lack of context of what needs to be done
  • pressure from others on this change (e.g. management)

Let's take a closer look at each of these, adding some more context.

Unfamiliar with codebase

You arrive for work one day and your manager (if you have one) informs you there is a requirement for something to be changed on system x. The name system x rings a bell, was it from a water cooler chat last week? You know what's coming. They ask who would like to volunteer to implement this change in the dark and mysterious system x. So like the good person you are, you raise your hand and announce "I will!". Everyone is staring at you, in envy of your bravery.

You now wonder what you have got yourself into, and soon you will find out.

After you clone the project, you search in vain for a README, this search continues as you tell yourself "there must be something to tell me about this system". Well sadly for you there isn't, this project was finished two years ago and the third party who built it left immediately.

Without any documentation or anybody to ask, you are left all alone. Sure you can ask for help but nobody will help because everyone who knew anything about the system left a long time ago.

The scenario I have just described can create fear.

New to the team

Day one, an exciting day indeed. It is your first day on your new team, you want to be accepted by your new team, and so feel the need to prove yourself (no bread jokes here). It is the standup and you are extremely excited to pick up a story, so like Mr. Unfamiliar in the previous scenario, you volunteer.

As you settle in back at your desk, the reality sets in. Sure, you know the language and have been using it in production for a while now. But as you get further and further into the ticket, you realise you might have to change a few different parts of the system. This feeling of not wanting to screw up your first feature on the new team fills you with fear:

  • "what if I break something?"
  • "how will the team lead react?"

The scenario I have just described can create fear.

Lack of context

This can be found in both the previous sections, in that Mr. Unfamiliar:

  • did not have any documentation to work with
  • had not previously worked with the codebase

and Mrs. New:

  • possibly did not have sufficient knowledge of the system in her new team

Therefore, these can be categorised as symptoms of fear, they culminate with other factors to create a recipe for FDD.

Context is everything, and if I have not done a good enough job of setting this at the start of the post, then you will probably be wondering what I am talking about right now. As a reader, did the fact that I switched the format from the previous section throw you? Context is delicate, and assuming that you incorrectly framed a piece of information, the recipient(s) of this will now have a broken-context.

Many of us will have experienced a broken-context, and some examples are below:

  • a user story where the details are vague and fuzzy
  • unsure why a particular story is relevant
  • uncertain how your team fits into the bigger picture

To keep scope-creep from happening here, I will leave it at that. Just be aware that a lack of context can be a contributing factor to FDD.

Pressure from others

"Is it ready yet?" is the sound of your manager. Now, you like your manager, but the way he seems stuck to your desk when something "needs" to be delivered can sometimes be distracting. This is the story of pressure, and how it can evoke fear.

The pressure applied to you by your manager might make you fearful of what you are doing. It might even result in you doing something that is rushed and could actually make the system worse.

The scenario I have just described can create fear.

2. Where the fear leads

We have looked at what can create fear, now we look at what fear can do. In particular, what havoc fear can reap on a codebase. It might start small, but as the FDD is practised time and time again, the codebase suffers.

Let's look at some code examples of how FDD can manifest itself.

Append-only programming

Imagine the following is a method within a system

method save(people) {
    for each person save them to the database

Now one day there is a requirement to also save products in a system, fear could cause someone to do the below:

method save(people, products) {
    for each person save them to the database

    for each product save them to the database

Resulting in a method which now saves people and products, the programmer has appended a new feature to an existing feature, without considering whether this is the right thing to do. This is what fear does, it makes us miss things, a step in a process.

Furthermore, what if there is a requirement to save dogs in the system (what kind of system is this), if FDD takes the guise of append-only programming you might see:

method save(people, products, dogs) {
    for each person save them to the database

    for each product save them to the database

    for each dog save them to the database

Many could argue "well it's all in one place isn't it?". This is true, it most definitely is and this is in danger of becoming a very large and unwieldy method, with low cohesion. It does not stop there, it also means:

  • merging code is going to be a nightmare due to many people touching the same method for multiple reasons
  • it is much harder to identify who owns this method, due to the "save whatever you want" code present in there
  • more time consuming to implement features because you will have to resolve merge conflicts very frequently

The cascading effects of append-only programming are very real, and will have could have been mitigated by taking more time, with the absence of fear, to think about the change being made to a software system.

Copy and paste programming

There are other ways FDD can inflict pain on a codebase, one such way is copy and paste programming. Let's look at an example to help demonstrate this. Imagine in a codebase there is some code which retrieves data from a database, namely selecting all products where their price is greater than £100:

method getProductsOverOneHundredPounds() {
    select all products where price is greater than £100
    return products found

Now the above is pseudo-code, but imagine that in the actual code the first line of the method contains some SQL query that will be responsible for selecting the products, based on the aforementioned criteria.

What if, due to fear a programmer when having to perform the exact same query copies the code elsewhere:

method getProductsOverOneHundredPounds() {
    select all products where price is greater than £100
    return products found

method howManyProductsAreOverOneHundredPounds() {
    select all products where price is greater than £100
    return how many products found 

Now, this choice means that the SQL required to execute this query is now spread over two places in the codebase. This will create many problems:

  • if the query is to be changed (e.g. schema changes), it has to be done in two places, and a developer won't necessarily know this is the case
  • who owns the data? Should the second method know how to get this information, or should it simply call another part of the system (e.g. getProductsOverOneHundredPounds) to get this information (not knowing or caring how this is done)? This can be achieved by modularising code in your codebase.

Tunnel-vision programming

This infliction on a codebase can be found in both the aforementioned examples. It is simply when one is so focused on a particular task, that they do not step back to see the bigger picture. You are so concerned with implementing feature x, that you do not consider how it fits together with y and z.

Tunnel-vision programming could be described as selfish, I might be tempted to define it as the below:

Satisfying one's immediate needs whilst degrading the health of the codebase

Now, this can happen with or without fear. There are many different types of people working on codebases all around the world. Not all of them will be motivated to keep a codebase tidy, the decisions made might be driven by many factors, including fear.

3. Where the fear stops

Everything before now has provided context of how a codebase can be negatively impacted by fear, now I want to look at some techniques and tips for how we can avoid FDD being practised on our codebases.


The title above is simple. Having meaningful tests can instill confidence that you are not breaking anything. If you are a practitioner of TDD, then this will also help you to have confidence, and most importantly for me, structure to how you work. Furthermore, testing can help provide a direction for the production code to follow, often providing an accessible way for teammates to clarify their understanding of requirements.

If you want to come along and change the below:

method getProductsOverOneHundredPounds() {
    select all products where price is greater than £100
    return products found

And in the codebase there is also a test for this:

method testForGetProductsOverOneHundredPounds() {
    get result from getProductsOverOneHundredPounds

    result should equal expected result

Then when you are going to make a change in getProductsOverOneHundredPounds, you will get quick feedback that something has been broken by the change you have made, because you will have run the tests (say it once more!). For instance, you might "accidentally" have changed the code to:

method getProductsOverOneHundredPounds() {
    select all products where price is greater than £1000
    return products found

Fortunately, your test might catch that extra 0 you added and you can revert your change. No fear.

Taking a step back

The technique of taking a step back from a situation is a skill that is not just appropriate for creating and designing software. However, in a software context it can be practised by methods such as the below:

  • having breaks during pairing sessions to reflect on what was done in the last session
  • taking time to review the design of a codebase/system at regular intervals
  • before rushing to merge some code, spending some time reading your code, analysing it
  • get someone else's view on your code/decision (feedback)

Now if this all sounds simple, there is a good reason for this. It is simple to explain but often people find this difficult in practice. For example, factors such as an inflated ego could mean that one rushes their code to be merged, without accepting the fact that it could be in a better place first.

It is important to note for readers not to take this advice to the extreme. Don't spend 10 days agonising over the name of a method/function, or spend months reviewing the design of your system. Of course, everything depends on context and spending 10 days agonising over the name of a method might be acceptable if you are a maintainer of a library where the public interfaces you provide to your consumers are of paramount importance. It depends!

A final message

This post provides examples of how fear can start, and where it can lead. As a reader (and maybe a developer/programmer/wizard) you are in control, it is your decisions and those of your teammates that will decide whether your code is consumed by fear, or guarded by courage.

We are all in this together trying to do our best, and if you spot someone practising FDD, help them out and share the wisdom.

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