created new testcase for modulo operator

test/test.cpp

@@ -7,3 +7,9 @@ TEST_CASE( "some example calculations", "[calc]") {
   REQUIRE( evaluate("12+2-3*") == 3 );
   REQUIRE( evaluate("32%") == 1 );
 }
+
+TEST_CASE( "Test modulo function", "[calc]") {
+  REQUIRE( evaluate("11%") == 0 );
+  REQUIRE( evaluate("32%") == 1 );
+  REQUIRE( evaluate("51%") == 4 );
+}