Added simple randomness test (Wald–Wolfowitz runs)

CMakeLists.txt

@@ -367,6 +367,7 @@ add_executable( all_tests tests/all_tests.cpp
                           tests/crypto/blind.cpp
                           tests/crypto/blowfish_test.cpp
                           tests/crypto/dh_test.cpp
+                          tests/crypto/rand_test.cpp
                           tests/crypto/sha_tests.cpp
                           tests/network/ntp_test.cpp
                           tests/thread/task_cancel.cpp

tests/crypto/rand_test.cpp

@@ -0,0 +1,41 @@
+#include <boost/test/unit_test.hpp>
+
+#include <fc/crypto/rand.hpp>
+
+static void check_randomness( const char* buffer, size_t len ) {
+    if (len == 0) { return; }
+    // count bit runs and 0's / 1's
+    unsigned int zc = 0, oc = 0, rc = 0, last = 2;
+    for (size_t k = len; k; k--) {
+        char c = *buffer++;
+        for (int i = 0; i < 8; i++) {
+            unsigned int bit = c & 1;
+            c >>= 1;
+            if (bit) { oc++; } else { zc++; }
+            if (bit != last) { rc++; last = bit; }
+        }
+    }
+    BOOST_CHECK_EQUAL( 8*len, zc + oc );
+    double E = 1 + (zc + oc) / 2.0;
+    double variance = (E - 1) * (E - 2) / (oc + zc - 1);
+    double sigma = sqrt(variance);
+    BOOST_CHECK( rc > E - sigma && rc < E + sigma);
+}
+
+BOOST_AUTO_TEST_SUITE(fc_crypto)
+
+BOOST_AUTO_TEST_CASE(rand_test)
+{
+    char buffer[128];
+    fc::rand_bytes( buffer, sizeof(buffer) );
+    check_randomness( buffer, sizeof(buffer) );
+}
+
+BOOST_AUTO_TEST_CASE(pseudo_rand_test)
+{
+    char buffer[10013];
+    fc::rand_pseudo_bytes( buffer, sizeof(buffer) );
+    check_randomness( buffer, sizeof(buffer) );
+}
+
+BOOST_AUTO_TEST_SUITE_END()