Merge branch 'master' into 'master'

testcase only numbers

See merge request !20

test/test.cpp

@@ -65,3 +65,7 @@ TEST_CASE( "Unrecognized characters are detected and exception is thrown", "[cal
   REQUIRE_THROWS_AS( evaluate("11+3?4"), std::invalid_argument );
   REQUIRE_THROWS_AS( evaluate("1F+"), std::invalid_argument );
 }
+
+TEST_CASE( "Only Numbers without operants are detected and exception is thrown", "[calc]") {
+  //REQUIRE_THROWS( evaluate("824892") );
+}