t: move reftable/tree_test.c to the unit testing framework

reftable/tree_test.c exercises the functions defined in
reftable/tree.{c, h}. Migrate reftable/tree_test.c to the unit
testing framework. Migration involves refactoring the tests to use
the unit testing framework instead of reftable's test framework and
renaming the tests to align with unit-tests' standards.

Also add a comment to help understand the test routine.

Note that this commit mostly moves the test from reftable/ to
t/unit-tests/ and most of the refactoring is performed by the
trailing commits.

Mentored-by: Patrick Steinhardt <[email protected]>
Mentored-by: Christian Couder <[email protected]>
Signed-off-by: Chandra Pratap <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Chandra Pratap

Makefile

@@ -1336,6 +1336,7 @@ THIRD_PARTY_SOURCES += sha1dc/%
 UNIT_TEST_PROGRAMS += t-ctype
 UNIT_TEST_PROGRAMS += t-mem-pool
 UNIT_TEST_PROGRAMS += t-prio-queue
+UNIT_TEST_PROGRAMS += t-reftable-tree
 UNIT_TEST_PROGRAMS += t-strbuf
 UNIT_TEST_PROGRAMS += t-strcmp-offset
 UNIT_TEST_PROGRAMS += t-strvec
@@ -2681,7 +2682,6 @@ REFTABLE_TEST_OBJS += reftable/record_test.o
 REFTABLE_TEST_OBJS += reftable/readwrite_test.o
 REFTABLE_TEST_OBJS += reftable/stack_test.o
 REFTABLE_TEST_OBJS += reftable/test_framework.o
-REFTABLE_TEST_OBJS += reftable/tree_test.o
 
 TEST_OBJS := $(patsubst %$X,%.o,$(TEST_PROGRAMS)) $(patsubst %,t/helper/%,$(TEST_BUILTINS_OBJS))
 

reftable/reftable-tests.h

@@ -16,7 +16,6 @@ int pq_test_main(int argc, const char **argv);
 int record_test_main(int argc, const char **argv);
 int readwrite_test_main(int argc, const char **argv);
 int stack_test_main(int argc, const char **argv);
-int tree_test_main(int argc, const char **argv);
 int reftable_dump_main(int argc, char *const *argv);
 
 #endif

reftable/tree_test.c

@@ -8,7 +8,6 @@ int cmd__reftable(int argc, const char **argv)
 	basics_test_main(argc, argv);
 	record_test_main(argc, argv);
 	block_test_main(argc, argv);
-	tree_test_main(argc, argv);
 	pq_test_main(argc, argv);
 	readwrite_test_main(argc, argv);
 	merged_test_main(argc, argv);

t/helper/test-reftable.c

@@ -0,0 +1,60 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "test-lib.h"
+#include "reftable/tree.h"
+
+static int t_compare(const void *a, const void *b)
+{
+	return (char *)a - (char *)b;
+}
+
+struct curry {
+	void *last;
+};
+
+static void check_increasing(void *arg, void *key)
+{
+	struct curry *c = arg;
+	if (c->last)
+		check_int(t_compare(c->last, key), <, 0);
+	c->last = key;
+}
+
+static void t_tree(void)
+{
+	struct tree_node *root = NULL;
+	void *values[11] = { 0 };
+	struct tree_node *nodes[11] = { 0 };
+	size_t i = 1;
+	struct curry c = { 0 };
+
+	/*
+	 * 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);
+		i = (i * 7) % 11;
+	} while (i != 1);
+
+	for (i = 1; i < ARRAY_SIZE(nodes); i++) {
+		check_pointer_eq(&values[i], nodes[i]->key);
+		check_pointer_eq(nodes[i], tree_search(&values[i], &root, &t_compare, 0));
+	}
+
+	infix_walk(root, check_increasing, &c);
+	tree_free(root);
+}
+
+int cmd_main(int argc, const char *argv[])
+{
+	TEST(t_tree(), "tree_search and infix_walk work");
+
+	return test_done();
+}