905 add unit tests for enhancement config infrastructure

[thijsoo]

Context

• We want to add unit tests.

Summary

This PR can be summarized in the following changelog entry:

• Adds tests for the enhancement config infrastructure.

Relevant technical choices:

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• N/A

Relevant test scenarios

• [ ] Changes should be tested with the browser console open
• [ ] Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
• [ ] Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
• [ ] Changes should be tested on different browsers
• [ ] Changes should be tested on multisite

Test instructions for QA when the code is in the RC

• [X] QA should use the same steps as above.

QA can test this PR by following these steps:

Impact check

This PR affects the following parts of the plugin, which may require extra testing:

Other environments

• [ ] This PR also affects Shopify. I have added a changelog entry starting with [shopify-seo], added test instructions for Shopify and attached the Shopify label to this PR.

Documentation

• [ ] I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

Quality assurance

• [x] I have tested this code to the best of my abilities.
• [ ] During testing, I had activated all plugins that Yoast SEO provides integrations for.
• [ ] I have added unit tests to verify the code works as intended.
• [ ] If any part of the code is behind a feature flag, my test instructions also cover cases where the feature flag is switched off.
• [ ] I have written this PR in accordance with my team's definition of done.
• [ ] I have checked that the base branch is correctly set.
• [ ] I have ran grunt build:images and commited the results, if my PR introduces new images or SVGs.

Innovation

• [ ] No innovation project is applicable for this PR.
• [ ] This PR falls under an innovation project. I have attached the innovation label.
• [ ] I have added my hours to the WBSO document.

Fixes #

[coveralls]

Pull Request Test Coverage Report for Build 8318f10e7eaa281c1756d24dec7e22a9ebe8c201

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 51.903%

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Totals
Change from base Build ad4f5d1decd5ba72026241af5b5f9afbe1d92e93:	-0.5%
Covered Lines:	31868
Relevant Lines:	61801

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💛 - Coveralls