More tests

Tests for several files;
bugfix for `Enum.clamp` (with test);
fix doc as for ticket #511

The bug for `clamp` was that the first element of each batch was duplicated (the test showed `["aabc"; "ddef"; "gghi"; "jjk"]` instead of `["abcd"; "efgh"; "ijk"]`). Using `junk` it now passes.