Vulnerability detector test module refactor: test_validate_feed_content

[fedepacher]

Related issue
#2599

Description

This PR adds changes and enhancements to the testing framework for vulnerability detector.

The changes made are as follows:

Added

• Add testing module: test_validate_feed_content and data.

Improvements

• Added a new structure to the test.
• Refactor the test in order to get PASSED.

Tests

• All vulnerability detector tests
• test_download_feeds

Outputs

test_validate_feed_content

======================== test session starts =========================
platform linux -- Python 3.6.8, pytest-6.2.3, py-1.10.0, pluggy-0.13.1
rootdir: /mnt/qa/tests/integration, configfile: pytest.ini
plugins: metadata-1.11.0, testinfra-5.0.0, html-3.1.1
collected 38 items                                                   

test_vulnerability_detector/test_feeds/test_validate_feed_content.py . [  2%]
.....................................                          [100%]

=================== 38 passed in 409.23s (0:06:49) ===================