### Question:
DMNValidationServiceImpl implements DMNValidationService { @Override public boolean isValidVariableName(final String source) { return FEELParser.isVariableNameValid(source); }  @Override boolean isValidVariableName(final String source);  }### Answer:
@Test public void testIsValidVariableNameWhenSourceIsValid() { assertTrue(service.isValidVariableName("drools")); }
@Test public void testIsValidVariableNameWhenSourceIsNotValid() { assertFalse(service.isValidVariableName("9drools")); }