tests: use custom assertion define

tests/test_assert.h

@@ -0,0 +1,13 @@
+#pragma once
+
+#include <stdio.h>
+#include <stdio.h>
+
+#define TEST_ASSERT(x) { \
+  if (!((x))) { \
+    fflush(stdout); \
+    fprintf(stderr, "FAILED: [%s:%d] %s\n", __FILE__, __LINE__, #x); \
+    fflush(stderr); \
+    exit(1); \
+  } \
+}