Did a full code coverage review and improved many of the tests and a bunch of code. I'll do one more final walk through all the code before getting back to work on the new combat system.

tests/easings.cpp

@@ -0,0 +1,17 @@
+#include <catch2/catch_test_macros.hpp>
+#include "easings.hpp"
+#include <cmath>
+
+TEST_CASE("make sure the easing functions at least run", "[easings]") {
+  double out = ease::sine(1.3);
+  REQUIRE(out <= 1.0);
+
+  out = ease::out_circ(3.444);
+  REQUIRE(std::isnan(out));
+
+  out = ease::out_bounce(1.13);
+  REQUIRE(out <= 10 );
+
+  out = ease::in_out_back(3.4);
+  REQUIRE(out < 250.0);
+}