As programmers adopt test-driven development, they are going to prevent many defects that would have escaped to testers. Programmers that write unit tests just after programming are going to find many of the defects that would have escaped. Keep in mind that the programmer tests only check what the programmer thinks the code is supposed to do. The tests do not assure the code meets the customers’ needs. But making sure the code is doing what the programmer thinks it is supposed to do is needed for high quality systems. They work on purpose, rather than by the accident of offsetting defects.
Testers, and the whole team, are responsible for making sure the product does what they think the customer needs. These are different tests, they cover more code per test as well as checking the interactions between modules. As testers adopt automated testing, they need different skills than the manual tester that is following a script or exploring. Some adopt Acceptance Test Driven Development. For testers in this environment, the world is changing. Changing for the better with the intellectual challenges of automation, keeping the cost of retest low, and reducing the repetitive, error prone and boring manual tests. Not all manual tests go away, but we work to automate what is repetitive. In addition ATDD moves testers upstream from reacting to the code written to specifying system behavior by example.
All that said, most of the world of software development still practices Debug Later Programming and manual test, the same practices I used in my first job as a programmer. Congratulations for using 1979 programming techniques! We’ve learned a lot since then.
For some adopting TDD and ATDD is changing their world. For most it is not. There is so much legacy code out there, as well as people and organizations that do not know how or why to automate their tests, that the status quo of testing will likely have a long life.
Upper management actually asked me to share my TDD experience as well & so I just published an article internally to our Embedded Software newsletter describing how TDD helped my project. Here’s the summary from that article (I think the dates really say it all):
While in Singapore, we visited the Leonardo da Vinci exhibit at the Marina Bay ArtScience Museum. We took the guided tour with expert from Milan. We think he was a Catholic priest by the roman collar. We were both amazed at the great influence and knowledge da Vinci had in math, science, art, music, technology, weapons, architecture…
Kent Beck told me years ago, if the code does not need to work, then there is no need to test it. He continued and observed, why bother writing it if it does not need to work. Since hearing that and discovering how frequently I make coding mistakes, I want thorough tests.
Maybe you are asking yourself “I’ve got integration and system tests, why do I need unit tests?”. The answer is simple, simple math.
Here is a good question, and my reply, from a recent attendee of my Test-Driven Development for Embedded C training.
As I work more with TDD, one of the concepts I am still struggling to grasp is how to test “leaf” components that touch real hardware. For example, I am trying to write a UART driver. How do I test that using TDD? It seems like to develop/write the tests, I will need to write a fake UART driver that doesn’t touch any hardware. Let’s say I do that. Now I have a really nice TDD test suite for UART drivers. However, I still need to write a real UART driver…and I can’t even run the TDD tests I created for it on the hardware. What value am I getting from taking the TDD approach here?
One of the biggest challenges for someone experiencing TDD the first time is working in the small steps. The small steps of TDD appear to be an independent discovery of John Gall’s observation described in the Systems Bible:
I’ve heard people say that software should be like building. You make a plan; buy the materials; and build it. Would remodeling be like new construction? Kind of. You make a plan, find a contractor, agree on the specs, order materials, demo (demolish) the unwanted parts of the building and build it out. Simple step by step.
Does it go that way?
Do business people care about clean code? They behave like they don’t. Well, they do and I can prove it using proof by contradiction. For the best results, read this proof first.
Suppose that a business person does not care about clean code. The business person wants features and they want them fast. So they pressure engineers to just get the code working. This causes the code to deteriorate. The business person wants more features, but the code is a mess so features take longer to add and things that work start to break. If the business person wants features fast, they need clean code and if they need clean code they must care about it too, which contradicts the statement that business people don’t care about clean code. The contradiction proves the original supposition to be false, proving that business people care about code structure, even if they don’t realize it.
(this article is not just for embedded developers)
A few months back I was reading Doug Schmidt’s blog, on The Growing Importance of Sustaining Software for the DoD, and he made the claim
“although software does not wear out, firmware and hardware become obsolete, thereby requiring software modifications”.
It was a bit of a clarifying moment for me. Doug clarified two terms that I suppose were obvious, or maybe not. Software is this thing that can have a long useful life, where firmware is going to be regularly be made obsolete as hardware evolves.
I’d like to add to Doug’s statement:
although software does not wear out, it can be destroyed from within by unmanaged dependencies on firmware and hardware.
Think of all the code denied the potential long life of software due to being infected with dependencies on hardware.
Maybe you read Part 1 of this article. If you did you’ll know it concerns adding tests to legacy code (legacy code is code without tests). You will also know that the code has file scope functions and data that we want to test directly.
My opinion on accessing private parts of well designed code, is that you do not need to. You can test well design code through its public interface. Take it as a sign that the design is deteriorating when you cannot find a way to fully test a module through its public interface.
Part 1 showed how to
#include the code under test in the test file to gain access to the private parts, a pragmatic thing to do when wrestling untested code into a test harness. This article shows another technique that may have an advantage for you over the technique shown in Part 1. Including the code under test in a test case can only be done once in a test build. What if you need access to the hidden parts in two test cases? You can’t. That causes multiple definition errors at link time.
This article shows how to create a test access adapter to overcome that problem.