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NCrunch and Continuous Testing: The Must-Have Setup

Most of this post was taken from the transcript of my Pluralsight course on NCrunch. If you are interested in watching the course but are not a Pluralsight subscriber, feel free to email me or leave a comment requesting a trial, and I’ll get you a 7 day subscription to check it out.

Understanding the Legitimate, Root-Cause Objection to TDD

In my experience, there are three basic “camps” of reactions to the concept of test driven development (TDD) from those not experienced with it: willing students, healthy skeptics and reactionary curmudgeons. The first group is basically looking for a chance to practice and needs no convincing. The last group will have to be dragged along, kicking and screaming, and so there’s no persuading them without the threat of negative consequences. It is the middle group that tends to have rational objections, some of which are well-founded and others of which aren’t so much. A lot of the negative reaction from this group is the result of reacting to the misconceptions that I mentioned in this post about what TDD is and isn’t. But even once they understand how it works, there are still some fairly common and legitimate objections that are not simply straw man arguments.

  1. The most common and prevalent objection is that coding this way means that you’re doing a lot more work. You’re taking more time and writing more code and people don’t necessarily see the benefit, especially in cases where they already know what code they want to write.
  2. Many of the misconception objections and other inexplicable resistance is really the result of people simply not knowing how to write tests or practice TDD, and perhaps at times being reluctant to admit it. Others may freely admit it. Either way, the objection is that TDD, like any other discipline, would take time to learn and require an investment of effort.
  3. There is also more code that is going into a project since you now have an additional test class for each single class you would otherwise have created. More code means more maintenance time and effort.
  4. Many astute observers also realize that a lot of legacy code, particularly that involving large-work constructors, singletons, and static state is very hard to test, making attempts to do so effort-intensive.
  5. And, along the same lines , they also realize that there would be more effort required than simply learning how to do TDD – it would also mean learning different design techniques such as dependency injection, polymorphism, and inversion of control.

When you consider all of these objections, they all have a common thread. At the core of it, they’re really all variants on the theme of not having enough time. Writing the tests, maintaining the test code, learning new ways of doing things, and applying them to new and old code are all things that take time, and for most developers, time is precious. Someone selling TDD is a lot like someone selling you on a 401K: they’re convincing you that sacrificing now is going to be worth it later and asking you to take this, to some degree, on faith.

Could TDD be better?

Justifying the adoption of TDD to a healthy skeptic hinges largely on demonstrating that it provides a net benefit in terms of time, and thus cost. So how can these objections be reconciled and the concerns addressed?

Well first up are the learning curve oriented objections. And the truth is that there’s no way around this one being a time sink. Learning how to do TDD and learning how to write testable code are going to take time, no matter what. If you do not have the time to learn, this is a perfectly valid objection, but only in the shorter term. After all, we work in an industry where change is the only constant and learning new languages, frameworks, and methodologies is pretty much table stakes for staying relevant.

Regarding development time overall, a very common argument made by TDD proponents is that the practice saves time over the long haul. This is reminiscent of the parable of the tortoise and the hare where the TDD practitioner is a tortoise plodding along, getting everything right and the hare is generating reams of code quickly but with mistakes. The hare will declare himself done more quickly, but he’ll spend a lot more time later troubleshooting, reading log files, debugging, and fixing errors. The tortoise may not finish as quickly, but when he does, he truly is done.

But what about in the short term? Is there anything that can be done to make things go more quickly in the short term for TDD practitioners? Could we strap a rocket pack to the tortoise and make him go faster than the hare while preserving his accuracy?


Speeding up the Feedback Loop

What if I told you a story? What if I told you that you could write code and know whether or not it was working nearly instantaneously? In this world of development, you don’t have to wait while your application starts up, and then navigate through various user interface screens to get to the action that will trigger the bit of code you want to verify. There is no more repetitive clicking and typing and waiting for screens to load. In fact, in this world you don’t even need to build your project or compile your code. All you need to do is type and see, as you’re typing, whether or not the changes you’re making are right. And, you can see a visual metric for how much confidence you can have in your changes by virtue of how much your code is covered by the unit tests.
Does that story sound too good to be true? Well, I’ll admit that it does sound pretty good, but I’ll let you in on a little secret – it is true. There is a name for this paradigm, and it’s called “continuous testing.” And there are various tools out there for different platforms that make it a reality, right now as we speak.

To understand the magic of continuous testing, it’s essential to understand one of the most important, but often overlooked, concepts in computer science. I’m talking about the feedback loop. At its core, programming is a series of experiments. Whenever you approach a programming task, you have a code base that does something, and you have a goal to make it do something different or new. To achieve this goal, you identify intermediate behaviors that you’d like to see to mark progress, and then you make changes that you think will result in those behaviors. Then, you run the application to see if what you thought would happen does, in fact, happen.

For example, perhaps you want to have your application display customer information stored in a database to the screen when the user clicks a certain button. You might first say “forget the database – let’s just get the button click to result in some hard-coded value being displayed,” and then set about altering the code to make that happen. When you’d made your changes to the code, you’d run the program and click that button to see what had happened.

Considered closely, this process is actually a lot like the scientific method. For step (1) you read the code. For step (2) you hypothesize what you’ll need to do to the code. For step (3) you predict the outcome of your changes, and for step (4) you make the changes and observe the results. The amount of time that it takes to perform an iteration of your coding version of the scientific method is what I’m calling the “feedback loop.” How long does it take for you to have an idea, implement it, and verify that it had the desired effect?


In the early days of programming when the use of punch cards was common, feedback times were very lengthy. Programmers would reason carefully about everything that they did because feedback times were extremely slow, meaning mistakes were very costly. While many improvements have been made across the board to feedback times, situations persist to this day when the feedback loop is excruciatingly slow. This includes long running or resource-intensive applications and distributed systems with high latency. With such systems, programmers on projects often devise schemes to try to shorten the feedback loop, such as mocking out bottlenecks to allow fast verification of the rest of the system.

What they’re really trying to do is shorten the feedback loop to allow themselves to be more productive. When a great deal of time elapses between trying something and seeing what happens, attention tends to wander to distractions like twitter or reddit, exacerbating the inefficiency in this already-slow process. Developers innately understand this problem and are frustrated by the long build and run times of behemoth and slow-running applications.

To combat this problem, developers intuitively favor faster schemes. Ask yourself whether you prefer to work on a small project that builds quickly or a large one. How about a slow test suite versus a fast one? By speeding up the feedback loop you trade frustration and wandering attention span for engagement and a feeling of accomplishment. Techniques like relying on fast-running unit tests and keeping modules small and decoupled help a great deal with this, but we can get even faster.

If short feedback is good, immediate is definitely better. Anyone who has done extensive work at a command line or, in general used a Read-Evaluate-Print-Loop (REPL) understands this. Attention does not wander at all during a session like this. Historically, such a thing wasn’t possible in a compiled language, but with the advent of multicore systems and increasingly sophisticated compiler technology, times are changing. It is now possible to have a build running in the background of an IDE like Visual Studio even as you modify the code.


If you’ve been watching my series on building a chess game using TDD you couldn’t help but notice the red and green dots on the left side of the code window, since they catch the eye. What you were seeing was the tool, NCrunch, in action. Now it’s time to get properly acquainted.

NCrunch is a software product by Remco Software and was written by software developer Remco Mulder, who owns the company. It is a tool written specifically to allow developers to practice continuous testing in Visual Studio. NCrunch is a commercial product with a tiered pricing model and full-blown customer support. And it operates as a plugin to Visual Studio so there is no need to integrate or operate any kind of standalone application. It drops right in, comfortably with a tool with which you are already familiar.

For the first several years of its existence, NCrunch was free, since it was in an extended state of Beta release. During the course of these years, it grew a substantial and loyal user base. In the fall of 2012, Remco decided to issue version 1.0 and release NCrunch as a full, commercial product with a licensing model and production support. It is now on version 2.5 and is most certainly an excellent, commercial-grade product that is worth every penny.

As I write my code using this tool, you may notice things that I rarely or never do. I rarely, if ever, run an application. I rarely, if ever, use the unit test runner. I rarely even compile my code, though I do this sometimes simply because I happen to be quite accustomed to looking at compiler feedback in the errors window. Continuous testing tools like NCrunch may have been a novelty when they came out, but I would argue that they’re rapidly becoming table stakes for efficient development these days.

Before NCrunch, the viability of TDD for me was tied up in the idea that investing extra time up front meant that I wouldn’t later be revisiting my code, debugging, tweaking, fixing, when I was further removed and it’s more time consuming. With NCrunch, I don’t even need to make that case. Now, if you took TDD and NCrunch away, my development process would be substantially slower as I sat there waiting for the application to compile or the test runner to do its thing.

If you don’t have this, get it. You won’t be sorry. Forget clean code, unit testing, TDD, all of that stuff (well, not really — but indulge me here for a second). Just get this setup for the tight feedback loop alone. There is nothing like the feeling of productivity you get from typing a line of code and knowing in less than a second, without doing anything else, whether the change is what you want. That incredible power makes it all worth it — the learning curve of the tool, the cost of the tool, adopting TDD, learning to unit test. It’s like getting a car with 500 horse power and feeling that acceleration; it ruins you for anything less.

By the way, if you liked this post and you're new here, check out this page as a good place to start for more content that you might enjoy.
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dave falkner
dave falkner
10 years ago

I learned this lesson while working on an application which collected information from the user across a ~10 screen wizard. Then at the end, when the user clicked the “submit it all” button, tons of data processing would occur. Manually debugging the application to ensure my latest lines of code that I added to this final data processing was incredibly tedious, and being able to simply launch a test of my code proved a huge benefit.

I have since come to say that setting breakpoints and launching the debugger, particularly for freshly-written code, is a pretty big process smell.

Erik Dietrich
10 years ago
Reply to  dave falkner

Couldn’t agree more about the process smell. I cringe when I watch people developing this way and I think, “you must be so bored…” Every time I’ve figured something out to speed up my feedback loop, there’s no going back.

Rudi Larno
10 years ago

I’ve been bitten by the usefulness of NCrunch a number of times, where Visual Studio would produce some blue squiggle lines under some code, yet NCrunch would report all tests as green already. I’d then wonder why the compile error was there, rerun the NCrunch tests and only after a little while remember to hit Ctrl-B to have Visual Studio compile the code and be up to date 😉

Erik Dietrich
10 years ago
Reply to  Rudi Larno

I haven’t hit that, myself. If anything, I’ve had the opposite problem here and there — NCrunch goes yellow for non-compile and stays that way when I fix the error. If I Ctrl-Shift-B, it then sorts itself out. Doesn’t happen to me much, though particularly lately.

Sudhir Mangla
10 years ago

Please provide me trial for your NCrunch course. I am very much interested in learning about NCrunch

Erik Dietrich
10 years ago
Reply to  Sudhir Mangla

Can-do. Drop me an email at erik at daedtech, and I’ll reply with an activation code. (I won’t paste it here since the first person happening by would just snap it up).

Jacob Appleton
Jacob Appleton
10 years ago

Erik, have you used Continuous Test (http://www.continuoustests.com/)? How does it compare to NCrunch? Is the code coverage aspect of NCrunch that important (Without having yet watched your Pluralsight course on NCrunch, I believe this to be the key feature difference)?

Erik Dietrich
10 years ago
Reply to  Jacob Appleton

I haven’t used that product enough to speak very intelligently about it, but I do remember trying it out back when it was called Mighty Moose (and when it was a pay tool and NCrunch was free). I do recall that it lacked the visual trace into the code that NCrunch has. To the point, I’ll say that it isn’t just about knowing or visualizing the test coverage. It’s really about visualizing paths through the code and tracing them back to tests. For instance, NCrunch supports turning the dots off for all tests except for a single one, which turns… Read more »


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