Add test to detect save file shifting (#8030)

test/save.c

@@ -0,0 +1,35 @@
+#include "global.h"
+#include "pokemon_storage_system.h"
+#include "test/test.h"
+
+// If you would like to ensure save compatibility, update the values below with those for your hack. You can find these through the debug menu.
+// Please note that this simple check is not 100% foolproof, but should be able to catch most unintended shifts.
+#define T_SAVEBLOCK1_SIZE 15568
+#define T_SAVEBLOCK2_SIZE 3884
+#define T_SAVEBLOCK3_SIZE 4
+#define T_POKEMONSTORAGE_SIZE 34144
+
+TEST("SaveBlock1 is backwards compatible")
+{
+    EXPECT_EQ(sizeof(struct SaveBlock1), T_SAVEBLOCK1_SIZE);
+}
+
+TEST("SaveBlock2 is backwards compatible")
+{
+    EXPECT_EQ(sizeof(struct SaveBlock2), T_SAVEBLOCK2_SIZE);
+}
+
+TEST("SaveBlock3 is backwards compatible")
+{
+    EXPECT_EQ(sizeof(struct SaveBlock3), T_SAVEBLOCK3_SIZE);
+}
+
+TEST("PokemonStorage is backwards compatible")
+{
+    EXPECT_EQ(sizeof(struct PokemonStorage), T_POKEMONSTORAGE_SIZE);
+}
+
+#undef T_SAVEBLOCK1_SIZE
+#undef T_SAVEBLOCK2_SIZE
+#undef T_SAVEBLOCK3_SIZE
+#undef T_POKEMONSTORAGE_SIZE