Test for issue #1977

Test that reproduces issue #1977 and will fail on ArchLinux with
Boost version: 1.58.0-1
gcc version: 4.9.2-4

test/libevm/vm.cpp

@@ -438,6 +438,15 @@ void doVMTests(json_spirit::mValue& v, bool _fillin)
 
 BOOST_AUTO_TEST_SUITE(VMTests)
 
+// test that reproduces issue https://github.com/ethereum/cpp-ethereum/issues/1977
+BOOST_AUTO_TEST_CASE(u256_overflow_test)
+{
+	dev::u256 a = 14;
+	dev::bigint b = dev::bigint("115792089237316195423570985008687907853269984665640564039457584007913129639948");
+	// to fix cast `a` to dev::bigint
+	BOOST_CHECK(a < b);
+}
+
 BOOST_AUTO_TEST_CASE(vmtests)
 {
 	dev::test::executeTests("vmtests", "/VMTests",dev::test::getFolder(__FILE__) + "/VMTestsFiller", dev::test::doVMTests);