[Tarantool-patches] [PATCH v3 luajit 3/6] test: introduce utils.h helper for C tests

[Sergey Kaplun via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

This header contains generic init and close functions for tests and
helpers for loading auxiliary Lua script with functions to run inside a
C test.  See more information in the <README.md> file.

It will be properly used in the next commit.

Part of tarantool/tarantool#7900
---
 test/tarantool-c-tests/CMakeLists.txt |  3 ++
 test/tarantool-c-tests/README.md      | 36 +++++++++++++
 test/tarantool-c-tests/utils.h        | 75 +++++++++++++++++++++++++++
 3 files changed, 114 insertions(+)
 create mode 100644 test/tarantool-c-tests/README.md
 create mode 100644 test/tarantool-c-tests/utils.h

diff --git a/test/tarantool-c-tests/CMakeLists.txt b/test/tarantool-c-tests/CMakeLists.txt
index da128457..17255345 100644
--- a/test/tarantool-c-tests/CMakeLists.txt
+++ b/test/tarantool-c-tests/CMakeLists.txt
@@ -26,6 +26,9 @@ set_target_properties(libtest PROPERTIES
 # lj_arch.h in compiled test are consistent with the LuaJIT library
 # to link.
 AppendFlags(TESTS_C_FLAGS ${TARGET_C_FLAGS})
+# Use directory for absolute path to the Lua script helper. So,
+# test binary can be run from any directory.
+AppendFlags(TESTS_C_FLAGS "-D__LJ_TEST_DIR__='\"${CMAKE_CURRENT_SOURCE_DIR}\"'")
 
 set(CTEST_SRC_SUFFIX ".test.c")
 file(GLOB tests "${CMAKE_CURRENT_SOURCE_DIR}/*${CTEST_SRC_SUFFIX}")
diff --git a/test/tarantool-c-tests/README.md b/test/tarantool-c-tests/README.md
new file mode 100644
index 00000000..102ec151
--- /dev/null
+++ b/test/tarantool-c-tests/README.md
@@ -0,0 +1,36 @@
+This directory contains C tests for Tarantool's fork of LuaJIT.
+
+They should test C API, some unit functionality, etc..
+
+The group of unit tests is declared like the following:
+```c
+void *t_state = NULL;
+const struct test_unit tgroup[] = {
+      test_unit_new(test_base),
+      test_unit_new(test_simple),
+};
+return test_run_group(tgroup, t_state);
+```
+
+Sometimes we need to test C API for modules, that show some Lua metrics (like
+`luaM_metrics` or sysprof). In these cases, the required Lua script should be
+named like the following: `<ctestname-script.lua>` and contains a table with a
+bunch of Lua functions named the same as the unit C test, that uses this
+function.
+
+```lua
+local M = {}
+M.base = function()
+  -- ...
+end
+
+M.test_simple = function()
+  -- ...
+end
+
+return M
+```
+
+The script is loaded via `utils_load_aux_script(L, script_name)`. It loads the file
+and place the table with functions at the top of Lua stack. Each function is get
+from the table via `utils_get_aux_lfunc(L)` helper in the corresponding test.
diff --git a/test/tarantool-c-tests/utils.h b/test/tarantool-c-tests/utils.h
new file mode 100644
index 00000000..714aa61a
--- /dev/null
+++ b/test/tarantool-c-tests/utils.h
@@ -0,0 +1,75 @@
+#ifndef TARANTOOL_LUAJIT_TEST_UTILS_H
+#define TARANTOOL_LUAJIT_TEST_UTILS_H
+
+#include <limits.h>
+#include <string.h>
+
+#include "lauxlib.h"
+#include "lua.h"
+#include "luajit.h"
+#include "lualib.h"
+
+#include "test.h"
+
+#define UTILS_UNUSED __attribute__((unused))
+
+/* Generic init for our tests. */
+static lua_State *utils_lua_init(void)
+{
+	lua_State *L = luaL_newstate();
+	if (!L)
+		bail_out("Can't init Lua state");
+	/* Stop collector during library initialization. */
+	lua_gc(L, LUA_GCSTOP, 0);
+	luaL_openlibs(L);
+	lua_gc(L, LUA_GCRESTART, -1);
+	return L;
+}
+
+/* Generic close for our tests. */
+static void utils_lua_close(lua_State *L)
+{
+	lua_close(L);
+}
+
+/*
+ * Load the pair to the test file <filename-script.lua>.
+ * Each file should return the table with functions (named the
+ * same as the corresponding unit tests) to call in unit tests.
+ * Script file name is given as the second argument.
+ * Push the table with those functions on the Lua stack.
+ */
+UTILS_UNUSED static void utils_load_aux_script(lua_State *L, const char *file)
+{
+	/*
+	 * Format script name.
+	 * `__LJ_TEST_DIR__` is set via CMake.
+	 */
+	char script[PATH_MAX] = __LJ_TEST_DIR__;
+	char *script_name = script + sizeof(__LJ_TEST_DIR__) - 1;
+	/* Replace '\0' with '/'. */
+	*script_name++ = '/';
+	/* Append script filename. */
+	strcpy(script_name, file);
+
+	if (luaL_dofile(L, script) != LUA_OK) {
+		test_comment("Can't load %s: '%s'", script,
+			     lua_tostring(L, -1));
+		bail_out("Can't load auxiliary script");
+	}
+
+	if (!lua_istable(L, -1))
+		bail_out("Returned value from script is not a table");
+}
+
+/*
+ * Accept a table on top of the Lua stack which containing the
+ * function named as the unit test we currently executing.
+ */
+#define utils_get_aux_lfunc(L) do {					\
+	lua_getfield((L), -1, __func__);				\
+	if (!lua_isfunction((L), -1))					\
+		bail_out("Can't get auxiliary test function");		\
+} while (0)
+
+#endif /* TARANTOOL_LUAJIT_TEST_UTILS_H */
-- 
2.34.1