ncd: tests: value.ncd: add some more testing with different representations of strings

ncd/tests/value.ncd

@@ -198,6 +198,9 @@ process main {
     value(buf) v;
     val_equal(v, "123") a;
     assert(a);
+    v->substr("2") sub_v;
+    val_equal(sub_v, "3") a;
+    assert(a);
     v->append("456789012345");
     val_equal(v, "123456789012345") a;
     assert(a);
@@ -208,6 +211,20 @@ process main {
     val_equal(sub_v, "345") a;
     assert(a);
     
+    concat("hello", "world") cnc;
+    value(cnc) v;
+    val_equal(v, "helloworld") a;
+    assert(a);
+    v->substr("2") sub_v;
+    val_equal(sub_v, "lloworld") a;
+    assert(a);
+    v->append("!!");
+    val_equal(v, "helloworld!!") a;
+    assert(a);
+    v->substr("1") sub_v;
+    val_equal(sub_v, "elloworld!!") a;
+    assert(a);
+    
     exit("0");
 }