basic calculus test

test/test.cpp

@@ -2,7 +2,10 @@
 
 #include <catch2/catch.hpp>
 
-TEST_CASE( "some example calculations", "[calc]") {
+TEST_CASE( "basic calculus", "[calc]") {
   REQUIRE( evaluate("11+") == 2 );
   REQUIRE( evaluate("12+2-3*") == 3 );
+  REQUIRE( evaluate("21-") == 1);
+  REQUIRE( evaluate("42/") == 2); 
+  REQUIRE( evaluate("22*") == 4);
 }