add no default test

Author: phlptp

tests/ConfigFileTest.cpp

@@ -1016,15 +1016,18 @@ TEST_CASE_METHOD(TApp, "TOMLStringVector", "[config]") {
         out << "[default]\n";
         out << "zero1=[]\n";
         out << "zero2={}\n";
+        out << "zero3={}\n";
         out << "nzero={}\n";
         out << "one=[\"1\"]\n";
         out << "two=[\"2\",\"3\"]\n";
         out << "three=[\"1\",\"2\",\"3\"]\n";
     }
 
-    std::vector<std::string> nzero, zero1, zero2, one, two, three;
+    std::vector<std::string> nzero, zero1, zero2, zero3, one, two, three;
     app.add_option("--zero1", zero1)->required()->expected(0, 99)->default_str("{}");
     app.add_option("--zero2", zero2)->required()->expected(0, 99)->default_val(std::vector<std::string>{});
+    // if no default is specified the argument results in an empty string
+    app.add_option("--zero3", zero3)->required()->expected(0, 99);
     app.add_option("--nzero", nzero)->required();
     app.add_option("--one", one)->required();
     app.add_option("--two", two)->required();
@@ -1034,6 +1037,7 @@ TEST_CASE_METHOD(TApp, "TOMLStringVector", "[config]") {
 
     CHECK(zero1 == std::vector<std::string>({}));
     CHECK(zero2 == std::vector<std::string>({}));
+    CHECK(zero3 == std::vector<std::string>({""}));
     CHECK(nzero == std::vector<std::string>({"{}"}));
     CHECK(one == std::vector<std::string>({"1"}));
     CHECK(two == std::vector<std::string>({"2", "3"}));