Welcome!

Java IoT Authors: Zakia Bouachraoui, Elizabeth White, Liz McMillan, Pat Romanski, Yeshim Deniz

Related Topics: Java IoT

Java IoT: Blog Feed Post

Is Test Overlap A Necessary Evil?

The overlap is not total because a layer tend to reduce the granularity of the unhappy paths it faces internally

In a recent blog post titled "The Limitations of TDD", Jolt Awards colleague Andrew Binstock shared some reservations Cédric Beust has about TDD.

When a person of extensive experience like Cédric speaks about testing, you pay attention. And I did.

Among the very interesting quotes from Cédric that Andrew has reproduced, the following really struck me:

Another important point is that unit tests are a convenience for *you*, the developer, while functional tests are important for your *users*. When I have limited time, I always give priority to writing functional tests. Your duty is to your users, not to your test coverage tools.

You also bring up another interesting point: overtesting can lead to paralysis. I can imagine reaching a point where you don't want to modify your code because you will have too many tests to update (especially in dynamically typed languages, where you can't use tools that will automate this refactoring for you). The lesson here is to do your best so that your tests don't overlap.

Trust me, as a test-infected developer, I would love to stay in a state of self-delusion and pretend that test-induced paralysis doesn't exist. But that would be a lie: the reality is grimmer than the wonderland of testing I would wish to live in. The reality is that tests both encourage and resist change.

On the one hand, tests encourage and support refactoring: when the behavior of the application should not change but the code needs to be re-organized, tests are a blessing. They give you the courage to dare changing code because of the immediate feedback they give when you've been refactoring a little too aggressively. And this is priceless.

On the other hand, tests resist behavioral changes. Because tests have captured all the nitty-gritty of your application, when comes the time to change its behavior, you will need to invest time to adapt your tests accordingly, and this whether you rework the tests first or not. As Cédric pointed out, in a dynamically typed language, this is immensely painful as development tools are almost useless in assisting you with the required changes. Similarly, if you use mock objects, you are good for going down a deeper Circle of Hell, where more painful and frustrating manual fixes await you.

So, is there any hope out of this love / hate relationship? Knowing that "the only way to go fast is to go well" dumping tests altogether is certainly not an option. Could the solution lies in Cédric's very last words: "do your best so that your tests don't overlap"?

At this point, I don't know yet but I've decided that, as a starting point, I should start to estimate the amount of overlap I'm dealing with in the Erlang game server I'm working on. Interestingly, what I've found could pretty much apply to the vast majority of Java projects I've been previously working on. Maybe it applies to your projects too?
The first thing I've looked at is the testing overlap that exists between two layers of our application:
As you can see, the overlap exists because tests of the upper layer rely on mocks to simulate all the happy paths and most of the unhappy paths of the underlying layer.

The overlap is not total because a layer tend to reduce the granularity of the unhappy paths it faces internally in order to expose the upper layer to a limited amount of bad situations to deal with.

Hence the limited amount of mocked features in the overlap area.

When applied to a typical vertical slice of our system, it looks like this:

This is not too bad. Until the wind of feature change comes blowing on this mock-based card-house of tests, life is peachy.

Until now, the tests I have been looking at were only unit and database ones. If I add our functional tests on top of the overlap diagram, here is what I get:

Now the application container is also tested, plus we get an insane amount of overlap.

But the amount of overlap is not what I want to discuss first: it's the test coverage profile that I want to look at first. Notice how the functional tests explore less unhappy paths as they exercise deeper application layers. This can be explained simply: some unhappy paths are very hard to reproduce via the reduced set of functionalities exposed at the top level, oftentimes because they require a very specific and complex state to be established beforehand or conditions that could only be met in case of low level failures (loss of networking, for example).

It's obviously out of the question to consider dropping functional tests in order to reduce the testing overlap. As Cédric said, they are the only tests that have a true value for the end user of the system. My experience confirms that you can reach a nearly flawless first-time client integration if your functional tests have a coverage profile that is similar to the one in the last figure above.

The only problem lies in the quality of feedback you get from functional testing: because it's impossible to make the gory details of the errors encountered when exploring unhappy paths surface at the uppermost level, your system must have a solid logging strategy that allows you to precisely track issues, should you decide to code using functional tests as your only safety net.

So are the unit tests overlapped by the functional tests the ones that must go? Cédric again gives the answer: if time is short, it's better to focus on the functional tests. Of course, if you have a battery of unit tests in place, keep them.
But, maybe, just maybe, as you move to your next project, consider writing functional tests firsts? That way you would have built first the tests that truly matter and, if time permits, write unit tests as you implement the features expected by the functional tests.

Read the original blog entry...

More Stories By David Dossot

David Dossot has worked as a software engineer and architect for more than 14 years. He is a co-author of Mule in Action and is the project despot of the JCR Transport and a member of the Mule Community Committee. He is the project lead of NxBRE, an open source business rules engine for the .NET platform (selected for O'Reilly's Windows Developer Power Tools). He is also a judge for the Jolt Product Excellence Awards and has written several articles for SD Magazine. He holds a Production Systems Engineering Diploma from ESSTIN.

IoT & Smart Cities Stories
Bill Schmarzo, Tech Chair of "Big Data | Analytics" of upcoming CloudEXPO | DXWorldEXPO New York (November 12-13, 2018, New York City) today announced the outline and schedule of the track. "The track has been designed in experience/degree order," said Schmarzo. "So, that folks who attend the entire track can leave the conference with some of the skills necessary to get their work done when they get back to their offices. It actually ties back to some work that I'm doing at the University of San...
In his general session at 19th Cloud Expo, Manish Dixit, VP of Product and Engineering at Dice, discussed how Dice leverages data insights and tools to help both tech professionals and recruiters better understand how skills relate to each other and which skills are in high demand using interactive visualizations and salary indicator tools to maximize earning potential. Manish Dixit is VP of Product and Engineering at Dice. As the leader of the Product, Engineering and Data Sciences team at D...
When talking IoT we often focus on the devices, the sensors, the hardware itself. The new smart appliances, the new smart or self-driving cars (which are amalgamations of many ‘things'). When we are looking at the world of IoT, we should take a step back, look at the big picture. What value are these devices providing. IoT is not about the devices, its about the data consumed and generated. The devices are tools, mechanisms, conduits. This paper discusses the considerations when dealing with the...
Bill Schmarzo, author of "Big Data: Understanding How Data Powers Big Business" and "Big Data MBA: Driving Business Strategies with Data Science," is responsible for setting the strategy and defining the Big Data service offerings and capabilities for EMC Global Services Big Data Practice. As the CTO for the Big Data Practice, he is responsible for working with organizations to help them identify where and how to start their big data journeys. He's written several white papers, is an avid blogge...
Dynatrace is an application performance management software company with products for the information technology departments and digital business owners of medium and large businesses. Building the Future of Monitoring with Artificial Intelligence. Today we can collect lots and lots of performance data. We build beautiful dashboards and even have fancy query languages to access and transform the data. Still performance data is a secret language only a couple of people understand. The more busine...
If a machine can invent, does this mean the end of the patent system as we know it? The patent system, both in the US and Europe, allows companies to protect their inventions and helps foster innovation. However, Artificial Intelligence (AI) could be set to disrupt the patent system as we know it. This talk will examine how AI may change the patent landscape in the years to come. Furthermore, ways in which companies can best protect their AI related inventions will be examined from both a US and...
Enterprises have taken advantage of IoT to achieve important revenue and cost advantages. What is less apparent is how incumbent enterprises operating at scale have, following success with IoT, built analytic, operations management and software development capabilities - ranging from autonomous vehicles to manageable robotics installations. They have embraced these capabilities as if they were Silicon Valley startups.
Chris Matthieu is the President & CEO of Computes, inc. He brings 30 years of experience in development and launches of disruptive technologies to create new market opportunities as well as enhance enterprise product portfolios with emerging technologies. His most recent venture was Octoblu, a cross-protocol Internet of Things (IoT) mesh network platform, acquired by Citrix. Prior to co-founding Octoblu, Chris was founder of Nodester, an open-source Node.JS PaaS which was acquired by AppFog and ...
The deluge of IoT sensor data collected from connected devices and the powerful AI required to make that data actionable are giving rise to a hybrid ecosystem in which cloud, on-prem and edge processes become interweaved. Attendees will learn how emerging composable infrastructure solutions deliver the adaptive architecture needed to manage this new data reality. Machine learning algorithms can better anticipate data storms and automate resources to support surges, including fully scalable GPU-c...
Cloud-enabled transformation has evolved from cost saving measure to business innovation strategy -- one that combines the cloud with cognitive capabilities to drive market disruption. Learn how you can achieve the insight and agility you need to gain a competitive advantage. Industry-acclaimed CTO and cloud expert, Shankar Kalyana presents. Only the most exceptional IBMers are appointed with the rare distinction of IBM Fellow, the highest technical honor in the company. Shankar has also receive...