t/: migrate helper/test-example-decorate to the unit testing framework

helper/test-example-decorate.c along with t9004-example.sh provide
an example of how to use the functions in decorate.h (which provides
a data structure that associates Git objects to void pointers) and
also test their output.

Migrate them to the new unit testing framework for better debugging
and runtime performance.

Mentored-by: Christian Couder <chriscool@tuxfamily.org>
Mentored-by: Kaartic Sivaraam <kaartic.sivaraam@gmail.com>
Signed-off-by: Ghanshyam Thakkar <shyamthakkar001@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: spectre10

Makefile

@@ -793,7 +793,6 @@ TEST_BUILTINS_OBJS += test-dump-fsmonitor.o
 TEST_BUILTINS_OBJS += test-dump-split-index.o
 TEST_BUILTINS_OBJS += test-dump-untracked-cache.o
 TEST_BUILTINS_OBJS += test-env-helper.o
-TEST_BUILTINS_OBJS += test-example-decorate.o
 TEST_BUILTINS_OBJS += test-example-tap.o
 TEST_BUILTINS_OBJS += test-find-pack.o
 TEST_BUILTINS_OBJS += test-fsmonitor-client.o
@@ -1334,6 +1333,7 @@ THIRD_PARTY_SOURCES += compat/regex/%
 THIRD_PARTY_SOURCES += sha1collisiondetection/%
 THIRD_PARTY_SOURCES += sha1dc/%
 
+UNIT_TEST_PROGRAMS += t-example-decorate
 UNIT_TEST_PROGRAMS += t-mem-pool
 UNIT_TEST_PROGRAMS += t-strbuf
 UNIT_TEST_PROGRAMS += t-ctype

decorate.h

@@ -3,7 +3,7 @@
 
 /*
  * A data structure that associates Git objects to void pointers. See
- * t/helper/test-example-decorate.c for a demonstration of how to use these
+ * t/unit-tests/t-example-decorate.c for a demonstration of how to use these
  * functions.
  */
 

t/helper/test-example-decorate.c

@@ -29,7 +29,6 @@ static struct test_cmd cmds[] = {
 	{ "dump-split-index", cmd__dump_split_index },
 	{ "dump-untracked-cache", cmd__dump_untracked_cache },
 	{ "env-helper", cmd__env_helper },
-	{ "example-decorate", cmd__example_decorate },
 	{ "example-tap", cmd__example_tap },
 	{ "find-pack", cmd__find_pack },
 	{ "fsmonitor-client", cmd__fsmonitor_client },

t/helper/test-tool.c

@@ -23,7 +23,6 @@ int cmd__dump_split_index(int argc, const char **argv);
 int cmd__dump_untracked_cache(int argc, const char **argv);
 int cmd__dump_reftable(int argc, const char **argv);
 int cmd__env_helper(int argc, const char **argv);
-int cmd__example_decorate(int argc, const char **argv);
 int cmd__example_tap(int argc, const char **argv);
 int cmd__find_pack(int argc, const char **argv);
 int cmd__fsmonitor_client(int argc, const char **argv);

t/helper/test-tool.h

@@ -0,0 +1,80 @@
+#include "test-lib.h"
+#include "object.h"
+#include "decorate.h"
+#include "repository.h"
+
+struct test_vars {
+	struct object *one, *two, *three;
+	struct decoration n;
+	int decoration_a, decoration_b;
+};
+
+static void t_add(struct test_vars *vars)
+{
+	void *ret = add_decoration(&vars->n, vars->one, &vars->decoration_a);
+
+	if (!check(ret == NULL))
+		test_msg("when adding a brand-new object, NULL should be returned");
+	ret = add_decoration(&vars->n, vars->two, NULL);
+	if (!check(ret == NULL))
+		test_msg("when adding a brand-new object, NULL should be returned");
+}
+
+static void t_readd(struct test_vars *vars)
+{
+	void *ret = add_decoration(&vars->n, vars->one, NULL);
+
+	if (!check(ret == &vars->decoration_a))
+		test_msg("when readding an already existing object, existing decoration should be returned");
+	ret = add_decoration(&vars->n, vars->two, &vars->decoration_b);
+	if (!check(ret == NULL))
+		test_msg("when readding an already existing object, existing decoration should be returned");
+}
+
+static void t_lookup(struct test_vars *vars)
+{
+	void *ret = lookup_decoration(&vars->n, vars->one);
+
+	if (!check(ret == NULL))
+		test_msg("lookup should return added declaration");
+	ret = lookup_decoration(&vars->n, vars->two);
+	if (!check(ret == &vars->decoration_b))
+		test_msg("lookup should return added declaration");
+	ret = lookup_decoration(&vars->n, vars->three);
+	if (!check(ret == NULL))
+		test_msg("lookup for unknown object should return NULL");
+}
+
+static void t_loop(struct test_vars *vars)
+{
+	int i, objects_noticed = 0;
+
+	for (i = 0; i < vars->n.size; i++) {
+		if (vars->n.entries[i].base)
+			objects_noticed++;
+	}
+	if (!check_int(objects_noticed, ==, 2))
+		test_msg("should have 2 objects");
+}
+
+int cmd_main(int argc UNUSED, const char **argv UNUSED)
+{
+	struct object_id one_oid = { { 1 } }, two_oid = { { 2 } }, three_oid = { { 3 } };
+	struct test_vars vars = { 0 };
+
+	vars.one = lookup_unknown_object(the_repository, &one_oid);
+	vars.two = lookup_unknown_object(the_repository, &two_oid);
+	vars.three = lookup_unknown_object(the_repository, &three_oid);
+
+	TEST(t_add(&vars),
+	     "Add 2 objects, one with a non-NULL decoration and one with a NULL decoration.");
+	TEST(t_readd(&vars),
+	     "When re-adding an already existing object, the old decoration is returned.");
+	TEST(t_lookup(&vars),
+	     "Lookup returns the added declarations, or NULL if the object was never added.");
+	TEST(t_loop(&vars), "The user can also loop through all entries.");
+
+	clear_decoration(&vars.n, NULL);
+
+	return test_done();
+}