diff --git a/selfpatch/CMakeLists.txt b/selfpatch/CMakeLists.txt
index acd075e..5b26d44 100644
--- a/selfpatch/CMakeLists.txt
+++ b/selfpatch/CMakeLists.txt
@@ -1,8 +1,20 @@
+add_library(spslr_randomizer STATIC
+	src/randomizer.c
+)
+
+target_include_directories(spslr_randomizer PUBLIC
+	$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src>
+)
+
 add_library(spslr_selfpatch STATIC src/selfpatch.c src/randomizer.c src/env.c)
 
+target_link_libraries(spslr_selfpatch PUBLIC spslr_randomizer)
+
 target_include_directories(spslr_selfpatch PUBLIC
 	$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
 	$<INSTALL_INTERFACE:include>
 )
 
 target_include_directories(spslr_patchcompile PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/src) # For spslr_list.h
+
+add_subdirectory(test)
diff --git a/selfpatch/src/randomizer.c b/selfpatch/src/randomizer.c
index a162edd..d51a01c 100644
--- a/selfpatch/src/randomizer.c
+++ b/selfpatch/src/randomizer.c
@@ -60,10 +60,13 @@ int spslr_randomizer_get_target(uint32_t target, uint32_t* size, uint32_t* field
 }
 
 int spslr_randomizer_get_field(uint32_t target, uint32_t field, int field_idx_mode,
-		uint32_t* size, uint32_t* offset, uint32_t* initial_offset) {
+		struct spslr_randomizer_field_info* info) {
 	if (target >= spslr_target_cnt)
 		return -1;
 
+	if (!info)
+		return 0;
+
 	const struct spslr_target* t = &spslr_targets[target];
 
 	if (field >= t->fieldcnt)
@@ -85,14 +88,11 @@ int spslr_randomizer_get_field(uint32_t target, uint32_t field, int field_idx_mo
 			return -1;
 	}
 
-	if (size)
-		*size = of->size;
-
-	if (offset)
-		*offset = rf->offset;
-
-	if (initial_offset)
-		*initial_offset = of->offset;
+	info->size = of->size;
+	info->offset = rf->offset;
+	info->initial_offset = of->offset;
+	info->alignment = of->alignment;
+	info->flags = of->flags;
 
 	return 0;
 }
diff --git a/selfpatch/src/randomizer.h b/selfpatch/src/randomizer.h
index 34dbb76..d2bafaf 100644
--- a/selfpatch/src/randomizer.h
+++ b/selfpatch/src/randomizer.h
@@ -6,12 +6,20 @@
 #define SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL 1
 #define SPSLR_RANDOMIZER_FIELD_IDX_MODE_FINAL 2
 
+struct spslr_randomizer_field_info {
+	uint32_t size;
+	uint32_t offset;
+	uint32_t initial_offset;
+	uint32_t alignment;
+	uint32_t flags;
+};
+
 int spslr_randomizer_init();
 int spslr_randomize();
 void spslr_randomizer_clear();
 
 int spslr_randomizer_get_target(uint32_t target, uint32_t* size, uint32_t* fieldcnt);
 int spslr_randomizer_get_field(uint32_t target, uint32_t field, int field_idx_mode,
-	uint32_t* size, uint32_t* offset, uint32_t* initial_offset);
+	struct spslr_randomizer_field_info* info);
 
 #endif
diff --git a/selfpatch/src/selfpatch.c b/selfpatch/src/selfpatch.c
index 7a02aee..3b2cf6c 100644
--- a/selfpatch/src/selfpatch.c
+++ b/selfpatch/src/selfpatch.c
@@ -46,12 +46,11 @@ void reorder_object(void* dst, const void* src, uint32_t target) {
 	uint8_t* dst_countable = (uint8_t*)dst;
 
 	for (uint32_t i = 0; i < field_count; i++) {
-		uint32_t field_offset, field_size, field_initial_offset;
-		if (spslr_randomizer_get_field(target, i, SPSLR_RANDOMIZER_FIELD_IDX_MODE_FINAL,
-				&field_size, &field_offset, &field_initial_offset))
+		struct spslr_randomizer_field_info finfo;
+		if (spslr_randomizer_get_field(target, i, SPSLR_RANDOMIZER_FIELD_IDX_MODE_FINAL, &finfo))
 			spslr_env_panic("failed to get ordered field descriptor");
 
-		spslr_env_memcpy(dst_countable + field_offset, src_countable + field_initial_offset, field_size);
+		spslr_env_memcpy(dst_countable + finfo.offset, src_countable + finfo.initial_offset, finfo.size);
 	}
 }
 
@@ -118,46 +117,42 @@ int64_t spslr_calculate_ipin_value(uint32_t start) {
 				break;
 			case SPSLR_IPIN_OP_ADD_INITIAL_OFFSET:
 				{
-					uint32_t initial_offset;
+					struct spslr_randomizer_field_info finfo;
 					if (spslr_randomizer_get_field(op->op0.add_initial_offset_target,
-							op->op1.add_initial_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL,
-							NULL, NULL, &initial_offset))
+							op->op1.add_initial_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL, &finfo))
 						spslr_env_panic("failed to get initial field offset");
 
-					res += initial_offset;
+					res += finfo.initial_offset;
 				}
 				break;
 			case SPSLR_IPIN_OP_ADD_OFFSET:
 				{
-					uint32_t offset;
+					struct spslr_randomizer_field_info finfo;
 					if (spslr_randomizer_get_field(op->op0.add_initial_offset_target,
-							op->op1.add_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL,
-							NULL, &offset, NULL))
+							op->op1.add_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL, &finfo))
 						spslr_env_panic("failed to get initial field offset");
 
-					res += offset;
+					res += finfo.offset;
 				}
 				break;
 			case SPSLR_IPIN_OP_SUB_INITIAL_OFFSET:
 				{
-					uint32_t initial_offset;
+					struct spslr_randomizer_field_info finfo;
 					if (spslr_randomizer_get_field(op->op0.add_initial_offset_target,
-							op->op1.sub_initial_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL,
-							NULL, NULL, &initial_offset))
+							op->op1.sub_initial_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL, &finfo))
 						spslr_env_panic("failed to get initial field offset");
 
-					res -= initial_offset;
+					res -= finfo.initial_offset;
 				}
 				break;
 			case SPSLR_IPIN_OP_SUB_OFFSET:
 				{
-					uint32_t offset;
+					struct spslr_randomizer_field_info finfo;
 					if (spslr_randomizer_get_field(op->op0.add_initial_offset_target,
-							op->op1.sub_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL,
-							NULL, &offset, NULL))
+							op->op1.sub_offset_field, SPSLR_RANDOMIZER_FIELD_IDX_MODE_ORIGINAL, &finfo))
 						spslr_env_panic("failed to get initial field offset");
 
-					res -= offset;
+					res -= finfo.offset;
 				}
 				break;
 			case SPSLR_IPIN_OP_ADD_CONST:
diff --git a/selfpatch/src/spslr_list_link.h b/selfpatch/src/spslr_list_link.h
index 0486861..0418a3f 100644
--- a/selfpatch/src/spslr_list_link.h
+++ b/selfpatch/src/spslr_list_link.h
@@ -3,19 +3,19 @@
 
 #include "spslr_list.h"
 
-extern uint32_t spslr_target_cnt;
-extern struct spslr_target spslr_targets[];
+extern const uint32_t spslr_target_cnt;
+extern const struct spslr_target spslr_targets[];
 
-extern uint32_t spslr_target_field_cnt;
-extern struct spslr_target_field spslr_target_fields[];
+extern const uint32_t spslr_target_field_cnt;
+extern const struct spslr_target_field spslr_target_fields[];
 
-extern uint32_t spslr_ipin_cnt;
-extern struct spslr_ipin spslr_ipins[];
+extern const uint32_t spslr_ipin_cnt;
+extern const struct spslr_ipin spslr_ipins[];
 
-extern uint32_t spslr_ipin_op_cnt;
-extern struct spslr_ipin_op spslr_ipin_ops[];
+extern const uint32_t spslr_ipin_op_cnt;
+extern const struct spslr_ipin_op spslr_ipin_ops[];
 
-extern uint32_t spslr_dpin_cnt;
-extern struct spslr_dpin spslr_dpins[];
+extern const uint32_t spslr_dpin_cnt;
+extern const struct spslr_dpin spslr_dpins[];
 
 #endif
diff --git a/selfpatch/test/CMakeLists.txt b/selfpatch/test/CMakeLists.txt
new file mode 100644
index 0000000..daf43cd
--- /dev/null
+++ b/selfpatch/test/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_executable(spslr_randomizer_test randomizer_test.c)
+target_link_libraries(spslr_randomizer_test PRIVATE spslr_randomizer)
diff --git a/selfpatch/test/randomizer_test.c b/selfpatch/test/randomizer_test.c
new file mode 100644
index 0000000..73db796
--- /dev/null
+++ b/selfpatch/test/randomizer_test.c
@@ -0,0 +1,96 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include <spslr_list_link.h>
+#include <randomizer.h>
+
+void *spslr_env_malloc(size_t size) {
+	return malloc(size);
+}
+
+void spslr_env_free(void *ptr) {
+	free(ptr);
+}
+
+uint32_t spslr_env_random_u32(void) {
+	return ((uint32_t)rand() << 16) ^ (uint32_t)rand();
+}
+
+const uint32_t spslr_target_cnt = 1;
+const uint32_t spslr_target_field_cnt = 4;
+
+const struct spslr_target spslr_targets[] = {
+	{
+		.size = 24,
+		.fieldcnt = 4,
+		.fieldoff = 0,
+	},
+};
+
+const struct spslr_target_field spslr_target_fields[] = {
+	{ .offset = 0,  .size = 4, .alignment = 4, .flags = 0 },
+	{ .offset = 4,  .size = 4, .alignment = 4, .flags = 0 },
+	{ .offset = 8,  .size = 4, .alignment = 4, .flags = 0 },
+	{ .offset = 16, .size = 8, .alignment = 8, .flags = 0 },
+};
+
+static int check_target(uint32_t tidx) {
+	uint32_t tsize, fieldcnt;
+
+	if (spslr_randomizer_get_target(tidx, &tsize, &fieldcnt) < 0)
+		return -1;
+
+	uint32_t cur_end = 0;
+
+	for (uint32_t i = 0; i < fieldcnt; i++) {
+		struct spslr_randomizer_field_info finfo;
+		if (spslr_randomizer_get_field(tidx, i, SPSLR_RANDOMIZER_FIELD_IDX_MODE_FINAL, &finfo) < 0)
+			return -1;
+
+		if (finfo.offset < cur_end)
+			return -1;
+
+		if (finfo.offset % finfo.alignment != 0)
+			return -1;
+
+		if ((finfo.flags & SPSLR_FLAG_FIELD_FIXED) && finfo.offset != finfo.initial_offset)
+			return -1;
+
+		if (finfo.offset + finfo.size > tsize)
+			return -1;
+
+		cur_end = finfo.offset + finfo.size;
+	}
+
+	return 0;
+}
+
+int main(void) {
+	srand((unsigned)time(NULL));
+
+	for (uint32_t iter = 0; iter < 1000000; iter++) {
+		if (spslr_randomizer_init() < 0) {
+			fprintf(stderr, "init failed\n");
+			return 1;
+		}
+
+		if (spslr_randomize() < 0) {
+			fprintf(stderr, "randomize failed at iter %u\n", iter);
+			return 1;
+		}
+
+		for (uint32_t tidx = 0; tidx < spslr_target_cnt; tidx++) {
+			if (check_target(tidx) < 0) {
+				fprintf(stderr, "check failed at iter %u target %u\n", iter, tidx);
+				return 1;
+			}
+		}
+
+		spslr_randomizer_clear();
+	}
+
+	printf("ok: 1000000 iterations\n");
+	return 0;
+}