[GSoC][PATCH v6 0/5] t: port reftable/tree_test.c to the unit testing framework

[Chandra Pratap <chandrapratap3519@gmail.com>]

The reftable library comes with self tests, which are exercised
as part of the usual end-to-end tests and are designed to
observe the end-user visible effects of Git commands. What it
exercises, however, is a better match for the unit-testing
framework, merged at 8bf6fbd0 (Merge branch 'js/doc-unit-tests',
2023-12-09), which is designed to observe how low level
implementation details, at the level of sequences of individual
function calls, behave.

Hence, port reftable/tree_test.c to the unit testing framework and
improve upon the ported test. The first patch in the series is
preparatory cleanup, the second patch moves the test to the unit
testing framework, and the rest of the patches improve upon the
ported test.

Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>

---
Changes in v6:
- Fix a style issue in a comment introduced in patch 3

CI/PR: https://github.com/gitgitgadget/git/pull/1740

Chandra Pratap(5):
reftable: remove unnecessary curly braces in reftable/tree.c
t: move reftable/tree_test.c to the unit testing framework
t-reftable-tree: split test_tree() into two sub-test
t-reftable-tree: add test for non-existent key
t-reftable-tree: improve the test for infix_walk()

Makefile                       |  2 +-
reftable/reftable-tests.h      |  1 -
reftable/tree.c                | 15 +++-------
reftable/tree_test.c           | 60 ----------------------
t/helper/test-reftable.c       |  1 -
t/unit-tests/t-reftable-tree.c | 83 +++++++++++++++++++++++++++++++++++++
6 files changed, 89 insertions(+), 73 deletions(-)

Range-diff against v5:
1:  59d5c17d5e ! 1:  501ea6c05d t-reftable-tree: split test_tree() into two sub-test functions
    @@ t/unit-tests/t-reftable-tree.c: static void check_increasing(void *arg, void *ke
      	size_t i = 1;
     -	struct curry c = { 0 };

    - 	/* pseudo-randomly insert the pointers for elements between
    - 	 * values[1] and values[10] (included) in the tree.
    +-	/* pseudo-randomly insert the pointers for elements between
    +-	 * values[1] and values[10] (included) in the tree.
    ++	/* Pseudo-randomly insert the pointers for elements between
    ++	 * values[1] and values[10] (inclusive) in the tree.
    + 	 */
    + 	do {
    + 		nodes[i] = tree_search(&values[i], &root, &t_compare, 1);
     @@ t/unit-tests/t-reftable-tree.c: static void t_tree(void)
      		check_pointer_eq(nodes[i], tree_search(&values[i], &root, &t_compare, 0));
      	}
2:  c1ce79916b = 2:  ecadc1833e t-reftable-tree: add test for non-existent key
3:  d1a5ced526 = 3:  cda7509281 t-reftable-tree: improve the test for infix_walk()