Now have a simple stats test.

tests/stats.cpp

@@ -0,0 +1,27 @@
+#include <catch2/catch_test_macros.hpp>
+#include "stats.hpp"
+#include "rand.hpp"
+#include <cmath>
+#include <fmt/core.h>
+
+TEST_CASE("basic stats tests", "[stats]") {
+  Stats stat1;
+  stat1.sample(1.0);
+
+  for(int i = 0; i < 20; i++) {
+    double x = Random::normal(20.0,5.0);
+    stat1.sample(x);
+    REQUIRE(!std::isnan(stat1.stddev()));
+    REQUIRE(stat1.mean() < stat1.mean() + stat1.stddev() * 4.0);
+  }
+
+  stat1.dump();
+
+  stat1.reset();
+  REQUIRE(stat1.n == 0.0);
+
+  auto timer = stat1.time_start();
+  for(int i = 0; i < 20; i++) {
+    stat1.sample_time(timer);
+  }
+}