When running with -XX:+ExecuteInternalVMTest, we get the following verbose output:
...
Running test: Test_log_file_startup_truncation
Running test: Test_invalid_log_file
Running test: DirectivesParser_test
Internal error on line 1 byte 2: Directive missing required match.
  Got EOS.
  At '}'.
{}
Internal error on line 1 byte 3: Directive missing required match.
  At '}]'.
[{}]
Internal error on line 1 byte 3: Directive missing required match.
  At '},{}]'.
[{},{}]
Internal error on line 1 byte 2: Directive missing required match.
  At '},{}'.
{},{}
Syntax error on line 2 byte 3: DirectivesParser can only start with an array containing directive objects, or one single directive.
  At '['.
  [
    {
      match: "foo/bar.*",
      inline : "+java/util.*",
      PrintAssembly: true,
      BreakAtExecute: true,
    }
  ]
]

Value error on line 4 byte 20: The key 'PrintInlining' does not allow an array of values.
  At '['.
    PrintInlining: [
      true,
      false
    ],
  }
]

Warning: +LogCompilation must be set to enable compilation logging from directives
Warning: +LogCompilation must be set to enable compilation logging from directives
Value error on line 7 byte 9: Method pattern error: Missing leading inline type (+/-)
  At '"foo",'.
        "foo",
        "bar",
      ]
    }
  }
]

Value error on line 8 byte 9: Method pattern error: Missing leading inline type (+/-)
  At '"bar",'.
        "bar",
      ]
    }
  }
]

Key error on line 1 byte 7: Key 'c1' not allowed after 'c1' key.
  At 'c1:{c1:{c1:{c1:{c1:{c1:{}}}}}}}}]'.
[{c1:{c1:{c1:{c1:{c1:{c1:{c1:{}}}}}}}}]
Value error on line 5 byte 12: Key of type match needs a value of type string
  At 'true,'.
    match: true,
    inline: true,
    enable: true,
    c1: {
      preset: true,
    }
  }
]

Running test: Test_TempNewSymbol
Running test: VMStructs_test
...

It would be good to hide this output behind the -XX:+VerboseInternalVMTests flag.