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Unit testing is a type of software testing where individual components of code get tested. This is to make sure that each unit is performing the way it should. Unit testing is the smallest part of the software that you can test. It usually involves one or two inputs that result in a single output. There are two types of unit testing: manual and automated.
Automated is generally the preferred method as it saves the developer a lot of time and effort. To do unit testing, your developer needs to write clear test code to test a specific function against an expected outcome.
The tests will then run and any errors or failures to produce the expected outcome will be logged. NUnit is a unit testing framework that belongs to the xUnit family and it is written entirely in C. It provides support for all. It is an open source software which was initially ported from JUnit. The current production release is version 3 and has been completely rewritten to offer many new features. Many Java developers are well versed in writing unit tests.
These unit tests are automatically run during build time with the help of continuous integration tools like Jenkins or Team city. As the importance of automation testing is growing, unit testing frameworks such as JUnit are gaining traction.
JUnit is an open-source unit testing framework for a test-driven development environment. In this case, it is not running if part. Branch coverage ensures each branch in the program e. That means each branch has been executed at least once during testing. So, each branch condition must have been true at least once and false at least once during testing. Sorry for that bad explanation. Will clear that by the below example.
We can use the same example which we have used above. So that, the code will execute if condition like below. So here, the green coloured lines will execute branch. We have covered one path of the branch. But still, another path is there to test which else part. So, the 2nd test case will run through the else part. Just wait a minute. I have explained both the statement coverage and the branch coverage with the same example and the same test cases.
So, Does that mean, if we cover all the statements it will cover all the branches as well? In the above example YES. But if you see another example it is not true. For the above example, I am writing one test case. In such a case, the statement coverage is like below. The green coloured lines will be executed when condition is true. So now we will come to our question. Does that mean, we have achieved branch coverage also?
The point is to show how easy it is to unit test your code. See the MinUnit homepage. A CUnit implementation that is fairly new, and apparently still in early development. See the CUnit for Mr. Ando homepage.
Criterion is a cross-platform C unit testing framework supporting automatic test registration, parameterized tests, theories, and that can output to multiple formats, including TAP and JUnit XML. Each test is run in its own process, so signals and crashes can be reported or tested if needed.
See the Criterion homepage for more information. It can help to create Makefiles, generate massive test cases coded in minimal 'iteration tables', walk along state machines, generate C-stubs and more. The comparison function, though, is flexible. Thus, any type of script may be used for checking. It may be applied to any language that can produce standard output. It offers an optional BDD notation, a mocking library, the ability to run it in a single process to make debugging easier.
A test runner which discover automatically the test functions is available. But you can create your own programmatically.
All those features and more are explained in the CGreen manual. Wikipedia gives a detailed list of C unit testing frameworks under List of unit testing frameworks: C. Personally I like the Google Test framework. The real difficulty in testing C code is breaking the dependencies on external modules so you can isolate code in units. This can be especially problematic when you are trying to get tests around legacy code. In this case I often find myself using the linker to use stubs functions in tests.
This is what people are referring to when they talk about " seams ". In C your only option really is to use the pre-processor or the linker to mock out your dependencies. Note that you are actually including the C file and not the header file. This gives the advantage of access to all the static data members. Here I mock out my logger which might be in logger. This means that the test file compiles and links independently from the rest of the code base and executes in isolation.
As for cross-compiling the code, for this to work you need good facilities on the target. I have done this with googletest cross compiled to Linux on a PowerPC architecture. This makes sense because there you have a full shell and os to gather your results. For less rich environments which I classify as anything without a full OS you should just build and run on the host.
You should do this anyway so you can run the tests automatically as part of the build. Michael Feathers has an excellent book about testing legacy code. In one chapter he covers techniques for dealing with non-OO code which I highly recommend.
Edit : I've written a blog post about unit testing procedural code, with source available on GitHub. Edit : There is a new book coming out from the Pragmatic Programmers that specifically addresses unit testing C code which I highly recommend. Minunit is an incredibly simple unit testing framework. I'm using it to unit test c microcontroller code for avr. Unity - Highly recommended framework for unit testing C code. It's ideal for embedded systems as it's very lightweight and simple.
I had no problems getting it to work on the target platform as well as on the desktop. In addition to writing the unit tests, all that's required is:. The system needs to support a heap and some stdio functionality which not all embedded systems have.
But the code is simple enough that you could probably work in alternatives to those requirements if your platform doesn't have them. You also might want to take a look at libtap , a C testing framework which outputs the Test Anything Protocol TAP and thus integrates well with a variety of tools coming out for this technology. It's mostly used in the dynamic language world, but it's easy to use and becoming very popular.
There is an elegant unit testing framework for C with support for mock objects called cmocka. It only requires the standard C library, works on a range of computing platforms including embedded and with different compilers. The API is fully documented and several examples are part of the source code.
To get started with cmocka you should read the article on LWN. I didn't get far testing a legacy C application before I started looking for a way to mock functions. I needed mocks badly to isolate the C file I want to test from others. I gave cmock a try and I think I will adopt it. Cmock scans header files and generates mock functions based on prototypes it finds.
Mocks will allow you to test a C file in perfect isolation.
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