What a week! After multiple iterations in converting the t-hash.c test file to use the Clar testing framework, and with valuable guidance from my mentor, Patrick Steinhardt, I successfully submitted a patch accepted by the community. Link to commit here

Pre-Conversion Steps

The process began with me spending significant time understanding the existing hash test script, including its structure, functions, and macros. While analyzing the test setup, I noted custom assertions from the homegrown unit tests imported via the test-lib.h header file. The impostor syndrome I mentioned here crept in a little as I juggled learning and delaying the start of the conversion.

Eventually, I realized that the best way to learn was by doing. I decided to dive in, knowing I could ask my mentor for help. This approach enabled me to raise key, focused questions about specific functions and macros in the test script. As a result, I gained a much clearer understanding of the hash test structure.

Before diving into the conversion, I needed to understand the Clar testing framework and how it differed from the existing homegrown framework. I started by reviewing the Clar documentation and examining examples of existing test files (u-strvec.c, u-ctype.c) that had already transitioned to Clar. This gave me insight into its structure, such as how test suites and test cases were defined using simple function declarations rather than intricate macros. My mentor also gave me a link to the email thread discussion that birthed the conversion of homegrown unit tests to clar, and with his help, I was able to set clear objectives for the conversion.

t-hash.c code breakdown

The custom macro TEST_HASH_STR facilitated testing both SHA1 and SHA256 hashes for input strings by wrapping the core logic into a concise test statement. Similarly, TEST_HASH_LITERAL handled literal strings. These macros relied on Git’s homegrown framework to assert conditions and print diagnostic messages when assertions failed.

The macro check() acted as a lightweight assertion mechanism, signaling errors when a condition was not met. The function test_msg() printed diagnostic messages for failed checks. The function check_hash_data() abstracted the process of initializing, updating, and finalizing hash contexts using Git’s hash algorithms, and assertions verified that computed hashes matched expected values for each test case.

Conversion Phase

The conversion kicked off with the check_hash_data() function. The function was refactored to use clar assertions in place of the custom-made assertions used in the homegrown unit tests. Next were the macros TEST_HASH_STR, and TEST_HASH_LITERAL which followed a similar transformation by replacing the custom assersion with clar. The capacity to report a custom-made message in the event of any failure was lost after conversion, but Clar displays both the test suite names as well as the test function name, which makes up for this. This has been noted down to be implemented in Clar upstream.

Before conversion, the script had the function cmd_main() which served as the entry point to the different hash test cases. The core of the testing lies in using the two macros mentioned above. Each test cases was refactored as standalone function testing each scenario individually. This modular approach improves readability and makes it easier to maintain or expand specific test cases without affecting others. Functions like test_hash__aaaaaaaaaa_100000() and test_hash__alphabet_100000() handle resource allocation and deallocation (strbuf_release()) within their scope, ensuring memory is managed cleanly. This helps avoid memory leaks and improves the code’s overall robustness.

Difficulties

The major problem encountered was coming up with a sufficient commit message. In the Git project, the commit messages and the cover letter are just as important as the changes made, even more so in some cases. The clear articulation of the technical changes made during patch development proved a little difficult. A balance of concise communication with sufficient technical detail to explain the reasoning behind changes is instrumental to getting one’s changes accepted by the community.

Another problem faced was meeting up to Git’s code standards. Git’s code standards play a crucial role in ensuring the long-term success, maintainability, and collaborative development of the project. In achieving the standards, I had to make a few iterations to fix the code formatting of the changes made.

Next Steps

The next step involves converting the files earmarked for initial conversions found here, to use the Clar framework.