Add unit tests for the tid allocator

[loganek]

Also, as part of the PR I've added simple infrastructure to add more unit tests in the future. At the moment tests are only executed on Linux, but can be extended to other platforms if needed.

I'd like to get feedback on the approach for unit tests; we have extensive e2e tests (wasi, spec) but I think ability to run unit tests would allow us to test some of the smaller functionality quicker and make testing more granular.

I did use https://github.com/google/googletest/ as a framework; seems like it's quite popular in the industry, and nicely integrates with CMake. I didn't do any major research though so I'm open for suggestions. The major limitation is the fact that GTest requires C++ compiler, but not sure if that's an issue for testing infrastructure.

[yamt]

can't googletest test plain C code? (just asking, i'm not familiar with googletest.)

[loganek]

no, gtest is implemented fully in C++, therefore test files must be C++ files as well.

[yamt]

FYI, i have been using cmocka for the other C project on macOS and ubuntu w/o any major issues.
(i'm not saying cmocka is better than other framework. actually i dunno.
i'm just saying i can share my experience.)

sample code: https://github.com/yamt/toywasm/blob/master/test/test.c

its output:

[==========] tests: Running 8 test(s).
[ RUN      ] test_leb128
[       OK ] test_leb128
[ RUN      ] test_endian
[       OK ] test_endian
[ RUN      ] test_functype
[       OK ] test_functype
[ RUN      ] test_idalloc
[       OK ] test_idalloc
[ RUN      ] test_timeutil
[       OK ] test_timeutil
[ RUN      ] test_timeutil_int64
[       OK ] test_timeutil_int64
[ RUN      ] test_list
[       OK ] test_list
[ RUN      ] test_xstrnstr
[       OK ] test_xstrnstr
[==========] tests: 8 test(s) run.
[  PASSED  ] 8 test(s).

[loganek]

Thanks for sharing; I don't have a strong opinion, I used gtest because it nicely integrates with CMake, is quite widely used, well documented, and I'm quite familiar with it. But let's see if others have any preferences, I don't mind moving to other framework.

[yamt]

one negative thing in cmocka is that its "mocking" functionality assumes ld --wrap and thus doesn't work on macOS. (i simply don't use the mocking functionality.)

[eloparco]

I've used gtest in the past for c code. There are some annoyances, like having to explicitly cast the return type of a malloc to compile (for instance, char* c = (char*)malloc(10);). From what I remember it has no (great) support for mocking in c.
For the rest, I don't recall any meaningful constraints.

[eloparco]

Suggested change

	void SetUp() override
	void TidAllocatorTest()

I think constructors/destructors are the preferred way to do the same https://github.com/google/googletest/blob/main/docs/faq.md#should-i-use-the-constructordestructor-of-the-test-fixture-or-setupteardown-ctorvssetup

[loganek]

I'll stick to setup/teardown, mainly because of this:

in the body of a constructor (or destructor), it's not possible to use the ASSERT_xx macros. Therefore, if the set-up operation could cause a fatal test failure that should prevent the test from running, it's necessary to use abort and abort the whole test executable, or to use SetUp() instead of a constructor.