new file mode 100644
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+++ b/src/test/bignum_tests.cpp
@@ -0,0 +1,110 @@
+#include <boost/test/unit_test.hpp>
+#include <climits>
+
+#include "bignum.h"
+
+BOOST_AUTO_TEST_SUITE(bignum_tests)
+
+
+// For the following test case, it is useful to use additional tools.
+//
+// The simplest one to use is the compiler flag -ftrapv, which detects integer
+// overflows and similar errors. However, due to optimizations and compilers
+// taking advantage of undefined behavior sometimes it may not actually detect
+// anything.
+//
+// You can also use compiler-based stack protection to possibly detect possible
+// stack buffer overruns.
+//
+// For more accurate diagnostics, you can use an undefined arithmetic operation
+// detector such as the clang-based tool:
+//
+// "IOC: An Integer Overflow Checker for C/C++"
+//
+// Available at: http://embed.cs.utah.edu/ioc/
+//
+// It might also be useful to use Google's AddressSanitizer to detect
+// stack buffer overruns, which valgrind can't currently detect.
+
+// Let's force this code not to be inlined, in order to actually
+// test a generic version of the function. This increases the chance
+// that -ftrapv will detect overflows.
+void mysetint64(CBigNum& num, int64 n) __attribute__((noinline));
+
+void mysetint64(CBigNum& num, int64 n)
+{
+	num.setint64(n);
+}
+
+// For each number, we do 2 tests: one with inline code, then we reset the
+// value to 0, then the second one with a non-inlined function.
+BOOST_AUTO_TEST_CASE(bignum_setint64)
+{
+    int64 n;
+
+    {
+        n = 0;
+        CBigNum num(n);
+        BOOST_CHECK(num.ToString() == "0");
+        num.setulong(0);
+        BOOST_CHECK(num.ToString() == "0");
+        mysetint64(num, n);
+        BOOST_CHECK(num.ToString() == "0");
+    }
+    {
+        n = 1;
+        CBigNum num(n);
+        BOOST_CHECK(num.ToString() == "1");
+        num.setulong(0);
+        BOOST_CHECK(num.ToString() == "0");
+        mysetint64(num, n);
+        BOOST_CHECK(num.ToString() == "1");
+    }
+    {
+        n = -1;
+        CBigNum num(n);
+        BOOST_CHECK(num.ToString() == "-1");
+        num.setulong(0);
+        BOOST_CHECK(num.ToString() == "0");
+        mysetint64(num, n);
+        BOOST_CHECK(num.ToString() == "-1");
+    }
+    {
+        n = 5;
+        CBigNum num(n);
+        BOOST_CHECK(num.ToString() == "5");
+        num.setulong(0);
+        BOOST_CHECK(num.ToString() == "0");
+        mysetint64(num, n);
+        BOOST_CHECK(num.ToString() == "5");
+    }
+    {
+        n = -5;
+        CBigNum num(n);
+        BOOST_CHECK(num.ToString() == "-5");
+        num.setulong(0);
+        BOOST_CHECK(num.ToString() == "0");
+        mysetint64(num, n);
+        BOOST_CHECK(num.ToString() == "-5");
+    }
+    {
+        n = LLONG_MIN;
+        CBigNum num(n);
+        BOOST_CHECK(num.ToString() == "-9223372036854775808");
+        num.setulong(0);
+        BOOST_CHECK(num.ToString() == "0");
+        mysetint64(num, n);
+        BOOST_CHECK(num.ToString() == "-9223372036854775808");
+    }
+    {
+        n = LLONG_MAX;
+        CBigNum num(n);
+        BOOST_CHECK(num.ToString() == "9223372036854775807");
+        num.setulong(0);
+        BOOST_CHECK(num.ToString() == "0");
+        mysetint64(num, n);
+        BOOST_CHECK(num.ToString() == "9223372036854775807");
+    }
+}
+
+BOOST_AUTO_TEST_SUITE_END()