Unit tests for alias_unit added

test/unit_test/static/quantity_test.cpp

@@ -24,6 +24,7 @@
 #include "units/physical/si/area.h"
 #include "units/physical/si/frequency.h"
 #include "units/physical/si/velocity.h"
+#include "units/physical/si/volume.h"
 #include <chrono>
 #include <utility>
 
@@ -202,6 +203,13 @@ static_assert(999q_m < 1q_km);
 static_assert(1000q_m >= 1q_km);
 static_assert(1000q_m <= 1q_km);
 
+// alias units
+
+static_assert(2q_l + 2q_ml == 2002q_ml);
+static_assert(2q_l + 2q_ml == 2002q_cm3);
+static_assert(2q_l + 2q_cm3 == 2002q_ml);
+static_assert(2q_dm3 + 2q_cm3 == 2002q_ml);
+
 // is_quantity
 
 static_assert(Quantity<length<millimetre, int>>);