Even though not all errors are caught by these new tests, it could
expose if otb is broken or if processing api is changed to adopt
optional status of parameters at run-time.
`alg.processAlgorithm()` is running and failing correctly.
But `parameter.checkValueIsAcceptable()` and `alg.checkParameterValues()`
aren't working as expected.
This can easily go into GuiTests.py but we tend to keep it out due to
usage of create_from_metadata(). All widget in GuiTests uses
create_from_class() which will not work for this special widget
