1 files changed, 33 insertions, 0 deletions
diff --git a/crypto/test/src/util/utiltest/IntegersTest.cs b/crypto/test/src/util/utiltest/IntegersTest.cs
index a661144db..91c0bf2b6 100644
--- a/crypto/test/src/util/utiltest/IntegersTest.cs
+++ b/crypto/test/src/util/utiltest/IntegersTest.cs
@@ -32,5 +32,38 @@ namespace Org.BouncyCastle.Utilities.UtilTests
             Assert.AreEqual(31, Integers.NumberOfTrailingZeros(int.MinValue));
             Assert.AreEqual(32, Integers.NumberOfTrailingZeros(0));
         }
+
+        [Test]
+        public void TestPopCount()
+        {
+            Random random = new Random();
+
+            for (int pos = 0; pos <= 24; ++pos)
+            {
+                int seed = Integers.RotateLeft(random.Next(0xFFFFFF) << 8, pos);
+                ImplTestPopCountRange(seed, pos, 0xFF);
+            }
+        }
+
+        private static void ImplTestPopCountRange(int seed, int pos, int count)
+        {
+            for (int i = 0; i < count; ++i)
+            {
+                int n = seed + (i << pos);
+                int expected = SimpleBitCount(n);
+                Assert.AreEqual(expected, Integers.PopCount(n));
+                Assert.AreEqual(expected, Integers.PopCount((uint)n));
+            }
+        }
+
+        private static int SimpleBitCount(int n)
+        {
+            int count = 0;
+            for (int i = 0; i < 32; ++i)
+            {
+                count += (n >> i) & 1;
+            }
+            return count;
+        }
     }
 }