Posts Tagged unittest
As we all know, unit test has been a crucial part of software development. I feel I was walking on ice if I was coding without writing tests. But even if we have unit tests, things may still go wrong if the tests have bad coverage. Fortunately, there are many tools today to help us analyze our code and give us every detail of the quality of our unit tests. GNU gcov is such a tool for code compiled with GCC.
gcov is very easy to use. If you’re developing a C/C++ project, all you have to do is to compile your project with “-g -O0 –coverage”. “–coverage” is a synonym for-fprofile-arcs, -ftest-coverage(compiling) and-lgcov(linking). This tells the compiler to generate additional information and code needed by gcov.
OK, let’s run our tests. GCC will generate a bunch of files(profiles) that will be used later. These files know how your tests was executed and record many information such as arc transition counts and some summary information. Now we’re ready to view our test coverage now with gcov. But gcov doesn’t give us a report that is easy to read and it’s not convenient. Here comes the tool called “LCOV”.
Recently I started working on the libbash project. I will write several articles talking about it in future. Now I’d just like to write something about the problem we encountered during development.
Our project will be a shared library. The C++ visibility support could improve the overall performance. Put simply, it hides most of the ELF symbols which would have previously (and unnecessarily) been public. Well it’s good for the library, it’s not good for unit tests(namely gtest) because they need to know the symbols.
Of course we don’t want the unit tests to be part of our library. So we need to find some way to let the unit test know the symbols and separate them into different automake targets. Our first solution is to use hidden visibility for the library and create an internal target with default visibility for the unit test. However, that requires compiling the source code twice. Finally Petteri Räty come with a solution (He is too busy to write a post :P):
lib_LTLIBRARIES = libcppbash.la
libcppbash_la_SOURCES = blah
libcppbash_la_CXXFLAGS = $(AM_CXXFLAGS) -fvisibility=hidden -fvisibility-inlines-hidden
cppunittests_SOURCES = blah
cppunittests_LDADD = libcppbash.la $(GTEST_LIBS)
cppunittests_LDFLAGS = -static
Here’s his explanation:
libtool by default builds both a shared and a static library for our project. This is why you see it building things twice (with PIC and without). Giving -static to libtool is just telling it to use the static version. Using the static version means everything ends up in the unit test binaries.