diff --git a/test/test_binary.cpp b/test/test_binary.cpp
index 9878c608..30c1fd4f 100644
--- a/test/test_binary.cpp
+++ b/test/test_binary.cpp
@@ -62,6 +62,39 @@ size_t test_parity(T value)
   return count & 1;
 }
 
+// Power of 2.
+uint64_t test_power_of_2(int power)
+{
+  uint64_t result = 1;
+
+  for (int i = 0; i < power; ++i)
+  {
+    result *= 2;
+  }
+
+  return result;
+}
+
+// Fold bits.
+template <typename TReturn>
+TReturn test_fold_bits(uint64_t value, int size)
+{
+  int bits_remaining = 64;
+  uint64_t mask = test_power_of_2(size) - 1;
+  TReturn  result = 0;
+
+  while (bits_remaining > size)
+  {
+    result = result ^ (value & mask);
+    value  = value >> size;
+    bits_remaining -= size;
+  }
+
+  result = result ^ (value & mask);
+
+  return result;
+}
+
 namespace
 {
   SUITE(test_binary)
@@ -667,5 +700,75 @@ namespace
         CHECK_EQUAL(test_parity(value), etl::parity(value));
       }
     }
+
+    //*************************************************************************
+    TEST(test_fold_bits)
+    {
+      const uint64_t data = 0xF8E9DACBBCAD9E8F;
+
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  1), (etl::fold_bits<uint64_t,  1>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  2), (etl::fold_bits<uint64_t,  2>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  3), (etl::fold_bits<uint64_t,  3>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  4), (etl::fold_bits<uint64_t,  4>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  5), (etl::fold_bits<uint64_t,  5>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  6), (etl::fold_bits<uint64_t,  6>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  7), (etl::fold_bits<uint64_t,  7>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  8), (etl::fold_bits<uint64_t,  8>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data,  9), (etl::fold_bits<uint64_t,  9>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 10), (etl::fold_bits<uint64_t, 10>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 11), (etl::fold_bits<uint64_t, 11>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 12), (etl::fold_bits<uint64_t, 12>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 13), (etl::fold_bits<uint64_t, 13>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 14), (etl::fold_bits<uint64_t, 14>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 15), (etl::fold_bits<uint64_t, 15>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 16), (etl::fold_bits<uint64_t, 16>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 17), (etl::fold_bits<uint64_t, 17>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 18), (etl::fold_bits<uint64_t, 18>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 19), (etl::fold_bits<uint64_t, 19>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 20), (etl::fold_bits<uint64_t, 20>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 21), (etl::fold_bits<uint64_t, 21>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 22), (etl::fold_bits<uint64_t, 22>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 23), (etl::fold_bits<uint64_t, 23>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 24), (etl::fold_bits<uint64_t, 24>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 25), (etl::fold_bits<uint64_t, 25>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 26), (etl::fold_bits<uint64_t, 26>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 27), (etl::fold_bits<uint64_t, 27>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 28), (etl::fold_bits<uint64_t, 28>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 29), (etl::fold_bits<uint64_t, 29>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 30), (etl::fold_bits<uint64_t, 30>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 31), (etl::fold_bits<uint64_t, 31>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 32), (etl::fold_bits<uint64_t, 32>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 33), (etl::fold_bits<uint64_t, 33>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 34), (etl::fold_bits<uint64_t, 34>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 35), (etl::fold_bits<uint64_t, 35>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 36), (etl::fold_bits<uint64_t, 36>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 37), (etl::fold_bits<uint64_t, 37>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 38), (etl::fold_bits<uint64_t, 38>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 39), (etl::fold_bits<uint64_t, 39>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 40), (etl::fold_bits<uint64_t, 40>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 41), (etl::fold_bits<uint64_t, 41>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 42), (etl::fold_bits<uint64_t, 42>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 43), (etl::fold_bits<uint64_t, 43>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 44), (etl::fold_bits<uint64_t, 44>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 45), (etl::fold_bits<uint64_t, 45>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 46), (etl::fold_bits<uint64_t, 46>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 47), (etl::fold_bits<uint64_t, 47>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 48), (etl::fold_bits<uint64_t, 48>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 49), (etl::fold_bits<uint64_t, 49>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 50), (etl::fold_bits<uint64_t, 50>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 51), (etl::fold_bits<uint64_t, 51>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 52), (etl::fold_bits<uint64_t, 52>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 53), (etl::fold_bits<uint64_t, 53>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 54), (etl::fold_bits<uint64_t, 54>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 55), (etl::fold_bits<uint64_t, 55>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 56), (etl::fold_bits<uint64_t, 56>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 57), (etl::fold_bits<uint64_t, 57>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 58), (etl::fold_bits<uint64_t, 58>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 59), (etl::fold_bits<uint64_t, 59>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 60), (etl::fold_bits<uint64_t, 60>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 61), (etl::fold_bits<uint64_t, 61>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 62), (etl::fold_bits<uint64_t, 62>(data)));
+      CHECK_EQUAL(test_fold_bits<uint64_t>(data, 63), (etl::fold_bits<uint64_t, 63>(data)));
+    }
   };
 }