rna-transcription: specify error cases using error-object

[NobbZ]

Currently there are 3 error cases in rna-transcriptions canonical-data.json.

Those are specified using an expected value of null instead of the “new” and more flexible way of using an error object.

Should we change this? And is this error-object described/specified somewhere in a human readable way?

[Insti]

Yes we should change this.

The error object is specified in the README in the Test Data Format section.

if an error is expected (because the input is invalid, or any other reason), the value at "expected" should be an object containing exactly one property, "error", whose value is a string.

[ErikSchierboom]

Should we change this?

Absolutely!