[yul-phaser] Tests for random number generators

test/CMakeLists.txt

@@ -141,6 +141,7 @@ detect_stray_source_files("${libyul_sources}" "libyul/")
 set(yul_phaser_sources
     yulPhaser/Chromosome.cpp
     yulPhaser/Program.cpp
+    yulPhaser/Random.cpp
 
     # FIXME: yul-phaser is not a library so I can't just add it to target_link_libraries().
     # My current workaround is just to include its source files here but this introduces

test/yulPhaser/Random.cpp

@@ -0,0 +1,95 @@
+/*
+	This file is part of solidity.
+
+	solidity is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	solidity is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <tools/yulPhaser/Random.h>
+
+#include <boost/test/unit_test.hpp>
+
+#include <cassert>
+
+using namespace std;
+
+namespace solidity::phaser::test
+{
+
+BOOST_AUTO_TEST_SUITE(Phaser)
+BOOST_AUTO_TEST_SUITE(RandomTest)
+
+BOOST_AUTO_TEST_CASE(uniformRandomInt_returns_different_values_when_called_multiple_times)
+{
+	constexpr uint32_t numSamples = 1000;
+	constexpr uint32_t numOutcomes = 100;
+
+	vector<uint32_t> samples1;
+	vector<uint32_t> samples2;
+	for (uint32_t i = 0; i < numSamples; ++i)
+	{
+		samples1.push_back(uniformRandomInt(0, numOutcomes - 1));
+		samples2.push_back(uniformRandomInt(0, numOutcomes - 1));
+	}
+
+	vector<uint32_t> counts1(numSamples, 0);
+	vector<uint32_t> counts2(numSamples, 0);
+	for (uint32_t i = 0; i < numSamples; ++i)
+	{
+		++counts1[samples1[i]];
+		++counts2[samples2[i]];
+	}
+
+	// This test rules out not only the possibility that the two sequences are the same but also
+	// that they're just different permutations of the same values. The test is probabilistic so
+	// it's technically possible for it to fail even if generator is good but the probability is
+	// so low that it would happen on average once very 10^125 billion years if you repeated it
+	// every second. The chance is much lower than 1 in 1000^100 / 100!.
+	//
+	// This does not really guarantee that the generated numbers have the right distribution or
+	// or that they don't come in long, repeating sequences but the implementation is very simple
+	// (it just calls a generator from boost) so our goal here is just to make sure it's used
+	// properly and we're not getting something totally non-random, e.g. the same number every time.
+	BOOST_TEST(counts1 != counts2);
+}
+
+BOOST_AUTO_TEST_CASE(binomialRandomInt_returns_different_values_when_called_multiple_times)
+{
+	constexpr uint32_t numSamples = 1000;
+	constexpr uint32_t numTrials = 100;
+	constexpr double successProbability = 0.6;
+
+	vector<uint32_t> samples1;
+	vector<uint32_t> samples2;
+	for (uint32_t i = 0; i < numSamples; ++i)
+	{
+		samples1.push_back(binomialRandomInt(numTrials, successProbability));
+		samples2.push_back(binomialRandomInt(numTrials, successProbability));
+	}
+
+	vector<uint32_t> counts1(numSamples, 0);
+	vector<uint32_t> counts2(numSamples, 0);
+	for (uint32_t i = 0; i < numSamples; ++i)
+	{
+		++counts1[samples1[i]];
+		++counts2[samples2[i]];
+	}
+
+	// See remark for uniformRandomInt() above. Same applies here.
+	BOOST_TEST(counts1 != counts2);
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+BOOST_AUTO_TEST_SUITE_END()
+
+}