I wrote two negative tests for the Unparse capability of the TDML Runner, where I would expect Unparse Errors. In the first scenario, the element in the input infoset is longer than the specified length in the schema. In the second, the element is shorter than specified. In both cases, the data unparses with no error.

See tests:
negativeUnparseTest03
negativeUnparseTest04
In the following files:
daffodil-test/src/test/resources/edu/illinois/ncsa/daffodil/section00/general/testUnparserGeneral.tdml
daffodil-test/src/test/scala-debug/edu/illinois/ncsa/daffodil/section00/TestUnparserGeneralDebug.scala