Why HammocKing?
Short story short:
HammocKing automates the generation of mockups of C-code in
Google Test/Mock styles
or mockups, fakes, stubs of the framework of your choice.
=> Ready to unit test of legacy code in under a minute. <=
Short story long:
Unit testing
“The absence of unit tests may indicate a lack of maturity in engineering …”
“…unit tests should be performed by developers as soon as a function is coded…”
Prerequisites for a successful process implementation:
Unit test framework must be integral part of …
Mature
Simple-to-use
Well documented
Developer’s IDE/Editor
Build system,
Continuous Integration system.
Usecase
Problem: Big amount of legacy code base.
This often leads to a very long getting started time before you can write your first unit test.
Why?
(Embedded) software consists of a set of software units. They share data through interfaces.
“Legacy” code means that code base has grown WITHOUT unit tests.
(At least some of the) units have many interfaces.
Let’s isolate unit a to be item-under-test (iut) for unit testing. Such a unit usually consists of one c file. Occassionally it consists of more than one source files.
Without HammocKing
The typical mood of a developer who does that is …
In the language of a C/C++ developer the “required interfaces” are “external dependencies”. So when isolated, these external dependencies which are
global variables or
global functions
do not exist. You need some “glue code” between your isolated production unit (unit under test) and your test file.
When building the test executable the linker complains about them unless you define them. This you do usually either in the source code of your test file(s) or in dedicated source files or you dedicate special mock source file(s) for that.
Especially when beginning unit testing of large legacy units never have seen test driven developers’ hands it becomes very tedious to do the manual task of …
Filter the linker’s error messages for undefined reference. Then …
- For each reference …
Search through source code to find the declaration of that reference (symbol)
Add include of header file where declaration is found to test code
Convert the declaration to a definition and …
If the symbol is a function then write the body to establish the data flow between unit under test and test code (so write a mock, stub or fake).
Below example shows the linker’s output for just 2 undefine references:
gcc -c -g -MMD -o a.c.obj a.c
gcc -c -g -MMD -o a_test.c.obj a_test.c
gcc -g -o a_test.exe a.c.obj a_test.c.obj
c:/users/manna/scoop/apps/mingw-winlibs-llvm-ucrt/current/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: a.c.obj: in function `a_some_func':
C:\d\repos\hammock\doc\source\usage\examples\one_compile_unit/a.c:6: undefined reference to `b_getX'
c:/users/manna/scoop/apps/mingw-winlibs-llvm-ucrt/current/bin/../lib/gcc/x86_64-w64-mingw32/12.2.0/../../../../x86_64-w64-mingw32/bin/ld.exe: C:\d\repos\hammock\doc\source\usage\examples\one_compile_unit/a.c:8: undefined reference to `c_setY'
collect2.exe: error: ld returned 1 exit status
make: *** [makefile:14: a_test.exe] Error 1
PS C:\d\repos\hammock\doc\source\usage\examples\one_compile_unit>
Back on the abstract level what the developer manually does is to create such adaptors (Mocks) between production code and test code:
With HammocKing
Or you let hammocking do this tedious job of creating these adaptors:
PS C:\d\repos\hammock\doc\source\usage\examples\one_compile_unit> make
gcc -c -g -MMD -o a.c.obj a.c
python -m hammocking --source a.c --plink a.c.obj --style plain_c --outdir . -g
INFO: HammocKing: Will create mockup for function b_getX
INFO: HammocKing: Will create mockup for function c_setY
gcc -c -g -MMD -o a_test.c.obj a_test.c
gcc -c -g -MMD -o mockup.c.obj mockup.c
gcc -g -o a_test.exe a.c.obj a_test.c.obj mockup.c.obj
./a_test.exe
PS C:\d\repos\hammock\doc\source\usage\examples\one_compile_unit>
Remark: This means to can directly start with your (first) unit tests for that unit.
Google Test is only the default.
Why is the Google Test (including Google Mock) test framework the default?
See https://cuhkszlib-xiaoxing.readthedocs.io/en/latest/external/gtest/googletest/docs/FAQ.html
Mockups, stubs, fakes.
See https://stackoverflow.com/questions/346372/whats-the-difference-between-faking-mocking-and-stubbing
Test frameworks.
See https://en.wikipedia.org/wiki/List_of_unit_testing_frameworks#C
See Mockup styles.
Appendix
