Add Tests

[m3nu]

Every module will need some tests. I suggest one test-module per module. E.g. test_facturx.py, test_pdfwriter.py, etc.

There is already a folder with test PDFs. We could have some Json files to compare against for each.

[duskybomb]

Will be working on tests tomorrow. Making list of functions for which we need tests:

• _xml_from_file(): checking for pdf with and without embedded metadata.
  • for pdf without pdf check whether metadata has been added or not
  • what should I do for pdf with embedded data?
• write_pdf()
  • check for pdf in directory
• write_xml()
  • should I parse it and compare?

@m3nu feel free to add more.

[m3nu]

Those are good to start with.