Tests for formato_dbf.py module

[ABHISHEKSONI121]

Summary

Related to #161
This test file (test_formato_dbf.py) contains unit tests for the formato_dbf module. The tests cover the following functionality:

• Reading DBF files: The tests ensure that the leer function correctly reads data from DBF files and returns the expected dictionary structure.
• Writing DBF files: The tests verify that the escribir function writes data to DBF files in the correct format and structure.
• Handling different field types: The tests check that the module correctly handles various field types, such as numeric, alphanumeric, and date fields.
• Error handling: The tests ensure that the module gracefully handles error scenarios, such as missing or invalid files.

Checklist

• Classes, Variables, function and methods logic ok
• Comments written explaining what the code does
• All python code is PEP8 compliant (run black .)
• No lint issues (run flake8)
• Test coverage with pytest implemented
• Reviewers assigned (at least 1 mentor)

Manual test evidence