To all Companies Currently Recruiting

I am writing this on behalf of all developers/engineers out there. Please stop with the take home coding challenge questions. Really. Just stop it. They are a lazy and frankly an unprofessional way of sorting the wheat from the chaff. Before closing your browser in disgust hear me out on this one and hopefully I can convince you of the error of your ways.

There has become an alarming trend these days of companies during the hiring process to issue lengthy coding challenges in order to prove that the individual they are hiring knows their stuff. I totally understand why you might be doing this but frankly its flawed. Lets go through several reasons why.

1. It shows that you have a lack of regard for the individuals time. This is a serious red flag. After all if you fail to respect my time why should I respect yours? Consider it this way, for every hour of time that your test takes you are taking away 1 hour of that persons family/rest/sleep/eating/hobby time. What is your commitment in this situation? If you aren’t willing to invest the time in the hiring process then why should we? Sure you need to review the code (and hopefully give feedback) but that usually takes less than 15 minutes (yes I have done this and you can do it very quickly). The time investment balance is horribly skewed in your favour, which starts the relationship off to a bad start. Lets also consider those who do consulting or contracting outside. If you ask them to do a 3 hour coding challenge then you are asking them to forgo somewhere in the region of $300-700. Even worse is that usually at the end of these tests all you get back is “Pass” or “Fail”. Even when you do give some feedback there is no way it pays back the amount of time that went in.

2. Long tests are irrelevant anyway. When you set someone up to solve a problem that takes several hours you are setting them up to fail. The test you set is usually set up such that you are looking for a specific answer and only that answer. It might be obvious to you that using the strategy pattern is the best way to solve your test, but what about those who’s development backgrounds require business logic rules to be user editable and hence live in a database where it can be modified? You are also going to nitpick over every little detail in a classic case of bike shedding. “They didn’t clean up some spaces!” “They didn’t comment this method!” “They did comment this method!” Even aware of this problem I still find myself falling into the trap of nitpicking over the small stuff that usually doesn’t matter. You are going to be investing time in training them how you want things anyway so why expect them to know it without even working with you?

3. It’s going to drive away talented individuals. I am not counting myself in this category but I know of many talented dev’s who simply refuse to do any sort of test. Why? They have a huge online portfolios of work they have previously done. Why do you even ask for our Github/Gitlab profiles if not to look at them? Surely 5 minutes of looking though would let you know if this person is a pretender or knows their stuff.

4. The hiring process is skewed towards the hirer. People looking for work are usually in one of two situations. Either they have a role and are looking around or they don’t have one. Lets consider the risk for both groups.

For those with a job they will need to resign from their current position to take an opportunity with you. There is usually a probation period following the hiring that either party can say “No this isn’t for me lets agree to be friends”. The hiree is the one taking on the largest risk in this situation. They have already left what possibly was a stable situation for an unstable situation. The company takes on the risk of potentially investing in someone and they leave. Realistically though the company is in the position to hire so renumeration is the least of their problems. For the hiree though the potential is that they join and after a month get the boot. They are now without income and back to looking for a job, only now they are in the latter category.

For those without a job, they have the situation that they might find employment and in doing so passing on other opportunities only to get the boot after a few months. Once again its skewed towards the company.

5. They are easily gamed. A quick check on freelancer or other such sites shows that I can probably buy a solution to any coding challenge you have for less than $300. For a job with a steady pay-check even if its only for a few months (before you find out I can’t code a damn) this is a no brainer especially if I know my coding chops aren’t up to standard. But why pay at all? A lot of the solutions are posted on online forums and Github already. Heck just ask your best mate who happens to know their stuff to do it for you. Whats the cost to the organisation here? Well assuming you do hire me based on my fraudulent test I could lurk in the company for months, either contributing nothing or perhaps causing all sorts of damage. At the very least you have paid several months salary.

A-hah you say! I can defeat what you have written above! I will just have another test during the interview process I can hear you thinking. DING DING DING WINNER! However, if you are going to do that anyway why not drop the initial challenge? After all what are you gaining?

Here’s what I propose. Bring the person you want to interview in and have them actually code on a machine in front of you. Work through a few simple problems together. It dons’t need to be complex. Ask them to write a function that reverses all the words in a string but not the string itself. Ask them how to find elements that existing in list A that are not in B. Ask them why they implemented certain patterns, how did they decide on data types, why did they comment/not comment a method. Let them know in advance that this is what is going to happen and what will be expected. You will learn far more in this short investment of time then with any coding challenge. If you want to get more in depth then why not offer to pay them for a single day to come in and actually work. The monetary cost will be less than making the wrong hire and you both get to decide if things are going to work out.

The best interview process I have been with to date was actually the Microsoft one for a intern role many many moons ago. It involved several hours of interviews with different individuals discussing different technology roles to try and ascertain the best fit.

When I walked out (I didn’t get the role BTW) I felt like a better person. Not only were the discussions interesting, I learnt a lot from those conducting them and I felt like my time was valued. They even offered to cover my travel expenses which made me feel like they cared about my time investment. This is how the process is meant to work. Its as much about the person being interviewed as about the company. Consider it an investment in your advertising budget if you are tracking the time investment (yes it is an investment!) as a cost. Good interviews stick with people a long time and GREAT ones make those people want to praise your company.

More interview snippets….

Since I wrote the code to these snippets I thought I may as well add them here in case I ever need them again or want to review them. As the other interview ones they are the answers to a question I was asked, slightly modified to protect the innocent. These ones are written in Python.

Q. Write a function to reverse each word in a string.

def reverse_each_word(words):
    Reverse each word in a string 
    return " ".join([x[::-1] for x in words.split(' ')])

The only thing of note in here is the x[::-1] which is extended slice syntax which reverses a string. You could also to reversed(x) although I believe at the time of writing it is MUCH slower.

Q. Given two arrays find which elements are not in the second.

def find_not_in_second(first, second): 
    Find which numbers are not in the
    second array
    return [x for x in first if x not in second]

I am especially proud of the second snippet as it is very easy to read and rather Pythonic. It takes in two lists such as [1,2,3] and [2,3,6] and returns a new list with the missing elements.

Another day another interview…

Another day another interview. I actually have been getting some good results from them so far. In particular the last two I have been on. I will discuss them briefly.

The first had an interesting coding test. Rather then asking me to solve Fizzbuzz or implement a depth first algorithm over a binary tree (seriously, I have been programming for 10 years and never needed to do that. I can, but its something I did in uni and not really applicable to anything I have done since then). It was to implement a simple REST service.

You created your service, hosted it online (heroku was suggested as its free) passed in the URL to a form, submitted and it hit your service looking for error codes and correct responses/output to input. Since you got to implement it in any language you want I went with Python/Django and produced the following code.

def parse_json(self, data):
	filtered = self.filter_drm(data['payload'])
	filtered = self.filter_episode_count(filtered)

	return self.format_return(filtered)

def filter_drm(self, data):
	if data is None or data == []:
		return []

	result = [x for x in data if 'drm' in x and x['drm'] == True]
	return result

def filter_episode_count(self, data, count=0):
	if data is None or data == []:
		return []

	result = [x for x in data if 'episodeCount' in x and x['episodeCount'] > count]
	return result

def format_return(self, data):
	if data is None or data == []:
		return {"response": []}

	result = [{	"image": x['image']['showImage'], 
				"slug": x['slug'],
				"title": x['title']} for x in data 
				if 'image' in x and 'slug' in x and 'title' in x]
	return {"response": result}

Essentially its the code from the model I created. It takes in some JSON data, filters it by the field DRM and Episode count, then returns a subset of the data in it. The corresponding view is very simple, with just some JSON parsing (with error checks) and then calling the above code. I did throw in quite a few unit tests though to ensure it was all working correctly.

Thankfully, after writing the logic, some basic testing (curl to fake a response) it all looked OK to me. I uploaded on heroku (never used it before and it took most of the time) and submitted the form. First go everything worked correctly passing all of the requirements listed which made me rather happy.

As for the second interview, it raised a good question which highlights the fact while I know how to write a closure and lambda I cannot actually say what they are. It also highlighted I really need to get better at Javascript since while I am pretty comfortable with it on the front end for backend processes such as node.js I am an absolute notice.

For the first, I was right about a lambda, which is just an anonymous function. As for the second part a closure is a function which closes over the environment allowing it to access variables not in its function list. An example would be,

def function1(h):
    def function2():
        return h
    return function2()

In the above function2 closes over function1 allowing it to access the the variables in function1’s environment such as h.

The other thing that threw me was implementing a SQL like join in a nice way. See the thing is I have been spoilt by C# which makes this very simple using LINQ. You literally join the two lists in the same way SQL would and it just works. Not only that the implementation is really easy to read.

I came up with the following which is ugly for two reasons,

1. its not very functional
2. it has very bad  O(N^2) runtime performance.

var csv1 = [
    {'name': 'one'},
    {'name': 'two'}

var csv2 = [
    {'name': 'one', 'address': '123 test street'},
    {'name': 'one', 'address': '456 other road'},
    {'name': 'two', 'address': '987 fake street'},

function joinem(csv1, csv2) {
    var ret = [];
    $.each(csv1, function(index, value) {
        $.each(csv2, function(index2, value2) {
            if( == {

    return ret;

var res1 = joinem(csv1, csv2);

Assuming I get some more time later I want to come back to this. I am certain there is a nice way to do this in Javascript using underscore.js or something similar which is just as expressive as the LINQ version.

Sample Coding Test

Being in the job market again I been doing quite a few tests. Since I have already put in the effort to a test without result I thought I would post it here.

The test involved producing output from a supplied CSV input file which contained insurance claims. Something about taking the input and using it to predict future claims. Please forgive my explanation as I am not a financial expert. Anyway the idea was to take an input such as the following,

One, 1992, 1992, 110.0
One, 1992, 1993, 170.0
One, 1993, 1993, 200.0
Two, 1990, 1990, 45.2
Two, 1990, 1991, 64.8
Two, 1990, 1993, 37.0
Two, 1991, 1991, 50.0
Two, 1991, 1992, 75.0
Two, 1991, 1993, 25.0
Two, 1992, 1992, 55.0
Two, 1992, 1993, 85.0
Two, 1993, 1993, 100.0

into the following,

1990, 4
One, 0, 0, 0, 0, 0, 0, 0, 110, 280, 200
Two, 45.2, 110, 110, 147, 50, 125, 150, 55, 140, 100

The test was mostly about proving that you can write maintainable code which is unit testable and the like. Anyway here is my solution. It takes in a list of objects which represent each of the four columns of the input.

The feedback I received back was that the coverage I achieved was high (I had a collection of tests over the methods), the code clean and well documented.

public class TriangleCSVLine
    public string product { get; set; }
    public int originYear { get; set; }
    public int developmentYear { get; set; }
    public double incrementalValue { get; set; }

public List TranslateToOutput(List parsedCsv)
    var output = new List();

    // Sanity checks...
    if (parsedCsv == null || parsedCsv.Count == 0)
        return output;

    // Used to determine where we are looking
    var totalYears = parsedCsv.Select(x => x.developmentYear).Distinct().OrderBy(x => x);
    var minYear = totalYears.Min();
    var maxYear = totalYears.Max();

    foreach (var product in parsedCsv.Select(x => x.product).Distinct())
        // All of the products values and the years it has
        var productValues = parsedCsv.Where(x => product.Equals(x.product));
        var originYears = Enumerable.Range(minYear, (maxYear - minYear) + 1);

        var values = new List();

        foreach (var year in originYears)
            // For each of the development years for this "period"
            var developmentYears = parsedCsv.Where(x => x.originYear == year)
                                                .Select(x => x.developmentYear).Distinct();

            // If we have no development years
            // that means we have an origin year without a year 1 
            // development year. This means we have no idea how many values
            // of zero should be in the file, so lets bail
            // should probably go into a pre validation
            if (developmentYears.Count() == 0)
                throw new MissingOriginDevelopmentTrangleCSVException(
                    string.Format("Missing development years for origin {0} in product {1}", year, product)

            // The values are running values...
            // so we keep the total and increment it as we go
            double runningTotal = 0;
            foreach (var rangeYear in Enumerable.Range(developmentYears.Min(), (developmentYears.Max() - developmentYears.Min()) + 1))
                var value1 = productValues.Where(x => x.originYear == year && x.developmentYear == rangeYear).SingleOrDefault();
                if (value1 != null)
                    runningTotal += value1.incrementalValue;
        output.Add(string.Format("{0}, {1}", product, string.Join(", ", values)));

    return output;

private string GenerateHeader(List parsedCsv)
    // Get distinct list of all the years
    var years = parsedCsv.Select(x => x.developmentYear).Distinct();

    // 1990-1990 counts as 1 year so add one
    var developmentYears = (years.Max() - years.Min()) + 1; 
    var header = string.Join(", ", years.Min(), developmentYears);

    return header;