diff --git a/src/core_test/codec/common_code.cc b/src/core_test/codec/common_code.cc
index 3bd4ecd..68afc8a 100644
--- a/src/core_test/codec/common_code.cc
+++ b/src/core_test/codec/common_code.cc
@@ -198,8 +198,7 @@ TEST(CommonCode, code_string) {
 }
 
 TEST(CommonCode, DISABLED_global_verify) {
-    BS::thread_pool pool;
-    auto futures = pool.submit_blocks(0ULL, 0x10'0000'0000ULL, [](auto start, auto end) {
+    const auto result = parallel_spawn(0x10'0000'0000ULL, [](uint64_t start, uint64_t end) {
         std::vector<uint64_t> codes;
         for (uint64_t common_code = start; common_code < end; ++common_code) { // brute-force search
             if (CommonCode::check(common_code)) {
@@ -207,13 +206,6 @@ TEST(CommonCode, DISABLED_global_verify) {
             }
         }
         return codes;
-    }, 0x1000); // split as 4096 pieces
-
-    std::vector<uint64_t> result;
-    result.reserve(ALL_CASES_NUM_);
-    for (auto &future : futures) {
-        const auto data = future.get();
-        result.insert(result.end(), data.begin(), data.end()); // combine sections
-    }
+    });
     EXPECT_EQ(result, all_common_codes());
 }
diff --git a/src/core_test/codec/helper/codec.h b/src/core_test/codec/helper/codec.h
index f6e9baa..7d8182a 100644
--- a/src/core_test/codec/helper/codec.h
+++ b/src/core_test/codec/helper/codec.h
@@ -36,3 +36,19 @@ void common_code_parallel(std::function<void(std::span<CommonCode>)> &&func);
 #define COMMON_CODE_PARALLEL(impl) CODE_PARALLEL(Common, common, impl)
 
 // ----------------------------------------------------------------------------------------- //
+
+/// Calculate multiple ranges separately and combine the results.
+template<typename T, typename F>
+requires std::is_integral_v<T> && std::is_invocable_v<F, T, T>
+auto parallel_spawn(T limit, F &&func) -> std::invoke_result_t<F, T, T> {
+    BS::thread_pool pool;
+    std::invoke_result_t<F, T, T> result;
+    for (auto &&future : pool.submit_blocks((T)0, limit, func, 0x1000)) {
+        const auto data = future.get();
+        result.insert(result.end(), std::begin(data), std::end(data)); // combine sections
+    }
+    pool.wait();
+    return result;
+}
+
+// ----------------------------------------------------------------------------------------- //
diff --git a/src/core_test/codec/raw_code.cc b/src/core_test/codec/raw_code.cc
index 4547e0f..2ab3167 100644
--- a/src/core_test/codec/raw_code.cc
+++ b/src/core_test/codec/raw_code.cc
@@ -165,22 +165,14 @@ TEST(RawCode, DISABLED_global_verify) {
         return raw_code;
     };
 
-    BS::thread_pool pool;
-    auto futures = pool.submit_blocks(0ULL, 0x10'0000'0000ULL, [](auto start, auto end) {
+    const auto result = parallel_spawn(0x10'0000'0000ULL, [](uint64_t start, uint64_t end) {
         std::vector<uint64_t> codes;
         for (uint64_t common_code = start; common_code < end; ++common_code) {
             if (RawCode::check(force_convert(common_code))) {
-                codes.emplace_back(common_code); // store valid raw code
+                codes.emplace_back(common_code); // store valid code
             }
         }
         return codes;
-    }, 0x1000); // split as 4096 pieces
-
-    std::vector<uint64_t> result;
-    result.reserve(ALL_CASES_NUM_);
-    for (auto &future : futures) {
-        const auto data = future.get();
-        result.insert(result.end(), data.begin(), data.end()); // combine sections
-    }
+    });
     EXPECT_EQ(result, all_common_codes());
 }
diff --git a/src/core_test/codec/short_code.cc b/src/core_test/codec/short_code.cc
index ca0851d..c587ea9 100644
--- a/src/core_test/codec/short_code.cc
+++ b/src/core_test/codec/short_code.cc
@@ -222,8 +222,7 @@ TEST(ShortCode, code_string) {
 
 TEST(ShortCode, DISABLED_global_verify) {
     speed_up_reset();
-    BS::thread_pool pool;
-    auto futures = pool.submit_blocks(0U, SHORT_CODE_LIMIT, [](auto start, auto end) {
+    const auto result = parallel_spawn(SHORT_CODE_LIMIT, [](uint32_t start, uint32_t end) {
         std::vector<uint64_t> codes;
         codes.reserve(end - start);
         for (uint32_t short_code = start; short_code < end; ++short_code) {
@@ -232,13 +231,6 @@ TEST(ShortCode, DISABLED_global_verify) {
             codes.emplace_back(common_code.unwrap());
         }
         return codes;
-    }, 0x1000); // split as 4096 pieces
-
-    std::vector<uint64_t> result;
-    result.reserve(ALL_CASES_NUM_);
-    for (auto &future : futures) {
-        const auto data = future.get();
-        result.insert(result.end(), data.begin(), data.end()); // combine sections
-    }
+    });
     EXPECT_EQ(result, all_common_codes());
 }