diff --git a/test/concur/test_concur_concurrent.cpp b/test/concur/test_concur_concurrent.cpp
index 80c6210..91f16b7 100644
--- a/test/concur/test_concur_concurrent.cpp
+++ b/test/concur/test_concur_concurrent.cpp
@@ -122,12 +122,12 @@ void test_unicast(std::size_t np, std::size_t nc, std::size_t k) {
     typename concur::traits<PC>::context ctx {};
     for (;;) {
       std::this_thread::yield();
-      std::uint64_t i;
-      while (!pc.dequeue(imp::make_span(circ), hdr, ctx, i)) {
+      std::uint64_t v;
+      while (!pc.dequeue(imp::make_span(circ), hdr, ctx, v)) {
         if (running == 0) return;
         std::this_thread::yield();
       }
-      sum += i;
+      sum += v;
     }
   };
 
@@ -170,55 +170,120 @@ namespace {
 template <typename PC>
 void test_broadcast(std::size_t np, std::size_t nc, std::size_t k) {
   LIBIMP_LOG_();
+  {
+    concur::element<std::uint64_t> circ[32] {};
+    PC pc;
+    typename concur::traits<PC>::header hdr {imp::make_span(circ)};
+    ASSERT_TRUE(hdr.valid());
 
-  concur::element<std::uint64_t> circ[32] {};
-  PC pc;
-  typename concur::traits<PC>::header hdr {imp::make_span(circ)};
-  ASSERT_TRUE(hdr.valid());
+    auto push_one = [&, ctx = typename concur::traits<PC>::context{}](std::uint32_t i) mutable {
+      return pc.enqueue(imp::make_span(circ), hdr, ctx, i);
+    };
+    auto pop_one = [&, ctx = typename concur::traits<PC>::context{}]() mutable {
+      std::uint64_t i;
+      if (pc.dequeue(imp::make_span(circ), hdr, ctx, i)) {
+        return i;
+      }
+      return (std::uint64_t)-1;
+    };
+    auto pop_one_2 = pop_one;
 
-  auto push_one = [&, ctx = typename concur::traits<PC>::context{}](std::uint32_t i) mutable {
-    return pc.enqueue(imp::make_span(circ), hdr, ctx, i);
-  };
-  auto pop_one = [&, ctx = typename concur::traits<PC>::context{}]() mutable {
-    std::uint64_t i;
-    if (pc.dequeue(imp::make_span(circ), hdr, ctx, i)) {
-      return i;
+    // empty queue pop
+    ASSERT_EQ(pop_one(), (std::uint64_t)-1);
+
+    // test one push & pop
+    for (int i = 0; i < 32; ++i) {
+      ASSERT_TRUE(push_one(i));
+      ASSERT_EQ(pop_one(), i);
     }
-    return (std::uint64_t)-1;
-  };
-  auto pop_one_2 = pop_one;
+    for (int i = 0; i < 100; ++i) {
+      ASSERT_TRUE(push_one(i));
+      ASSERT_EQ(pop_one(), i);
+    }
+    ASSERT_EQ(pop_one(), (std::uint64_t)-1);
 
-  // empty queue pop
-  ASSERT_EQ(pop_one(), (std::uint64_t)-1);
+    // test loop push & pop
+    for (int i = 0; i < 10; ++i) ASSERT_TRUE(push_one(i));
+    for (int i = 0; i < 10; ++i) ASSERT_EQ(pop_one(), i);
+    ASSERT_EQ(pop_one(), (std::uint64_t)-1);
 
-  // test one push & pop
-  for (int i = 0; i < 32; ++i) {
-    ASSERT_TRUE(push_one(i));
-    ASSERT_EQ(pop_one(), i);
+    // other loop pop
+    for (int i = 0; i < 32; ++i) ASSERT_TRUE(push_one(i));
+    for (int i = 0; i < 32; ++i) ASSERT_EQ(pop_one_2(), i);
+    ASSERT_EQ(pop_one_2(), (std::uint64_t)-1);
+
+    // overwrite
+    ASSERT_TRUE(push_one(123));
+    for (int i = 1; i < 32; ++i) {
+      ASSERT_EQ(pop_one(), i);
+    }
+    ASSERT_EQ(pop_one(), 123);
+    ASSERT_EQ(pop_one(), (std::uint64_t)-1);
   }
-  for (int i = 0; i < 100; ++i) {
-    ASSERT_TRUE(push_one(i));
-    ASSERT_EQ(pop_one(), i);
+
+  log.info("\n\tStart with: ", imp::nameof<PC>(), ", ", np, " producers, ", nc, " consumers...");
+  {
+    struct Data {
+      std::uint64_t n;
+      std::uint64_t i;
+    };
+    concur::element<Data> circ[32] {};
+    PC pc;
+    typename concur::traits<PC>::header hdr {imp::make_span(circ)};
+    ASSERT_TRUE(hdr.valid());
+
+    constexpr static std::uint32_t loop_size = 100'0000;
+
+    std::atomic<std::uint64_t> sum {0};
+    std::atomic<std::size_t> running {np};
+    std::array<std::atomic<std::size_t>, 64> counters {};
+
+    auto prod_call = [&](std::size_t n) {
+      typename concur::traits<PC>::context ctx {};
+      for (std::uint32_t i = 1; i <= loop_size; ++i) {
+        std::this_thread::yield();
+        counters[n] = 0;
+        do {
+          ASSERT_TRUE(pc.enqueue(imp::make_span(circ), hdr, ctx, Data{n, i}));
+          std::this_thread::yield();
+          // We need to wait for the consumer to consume the data.
+        } while (counters[n] < nc);
+        if (i % (loop_size / 10) == 0) {
+          log.info("[", n, "] put count: ", i);
+        }
+      }
+      --running;
+    };
+    auto cons_call = [&] {
+      typename concur::traits<PC>::context ctx {};
+      std::array<std::uint64_t, 64> last_i {};
+      for (;;) {
+        std::this_thread::yield();
+        Data v;
+        while (!pc.dequeue(imp::make_span(circ), hdr, ctx, v)) {
+          if (running == 0) return;
+          std::this_thread::yield();
+        }
+        // The v.i variable always increases.
+        if (last_i[v.n] >= v.i) {
+          continue;
+        }
+        last_i[v.n] = v.i;
+        sum += v.i;
+        ++counters[v.n];
+      }
+    };
+
+    std::vector<std::thread> prods(np);
+    for (std::size_t n = 0; n < np; ++n) prods[n] = std::thread(prod_call, n);
+    std::vector<std::thread> conss(nc);
+    for (auto &c : conss) c = std::thread(cons_call);
+
+    for (auto &p : prods) p.join();
+    for (auto &c : conss) c.join();
+
+    EXPECT_EQ(sum, k * np * (loop_size * std::uint64_t(loop_size + 1)) / 2);
   }
-  ASSERT_EQ(pop_one(), (std::uint64_t)-1);
-
-  // test loop push & pop
-  for (int i = 0; i < 10; ++i) ASSERT_TRUE(push_one(i));
-  for (int i = 0; i < 10; ++i) ASSERT_EQ(pop_one(), i);
-  ASSERT_EQ(pop_one(), (std::uint64_t)-1);
-
-  // other loop pop
-  for (int i = 0; i < 32; ++i) ASSERT_TRUE(push_one(i));
-  for (int i = 0; i < 32; ++i) ASSERT_EQ(pop_one_2(), i);
-  ASSERT_EQ(pop_one_2(), (std::uint64_t)-1);
-
-  // overwrite
-  ASSERT_TRUE(push_one(123));
-  for (int i = 1; i < 32; ++i) {
-    ASSERT_EQ(pop_one(), i);
-  }
-  ASSERT_EQ(pop_one(), 123);
-  ASSERT_EQ(pop_one(), (std::uint64_t)-1);
 }
 
 } // namespace