feat: unit testing framework

[akselthomsen]

Summary

Updates the unit testing workflow for a component.

A component being tested now has it's own class (mighty_component_test) that tracks test coverage,
and a separate and dedicated child R session to execute code in.

The new workflow is a follows:

1. Create test component with get_test_component()
2. Assign input data with $assign()
3. Execute and track coverage with $eval()
4. Retrieve results with $get()
5. Test results with expect_*() functions from {testthat}

The best way to see how a user will test components is see the updated tests/testthat/test-components.R that tests the dummy standard components currently inside the package.

I decided not to create a separate testing vignette in this PR.
I will include testing as part of the Getting Started vignette in #28.

Changes Made

• New mighty_component_test class. Inheriting from mighty_component_rendered.
• Corresponding get_test_component() function. On exit it by default checks if all lines of the test component has been covered by unit tests.
• The mighty_component_test has methods to $assign() and $get() variables from the child R session. The print() method also displays code coverage (in total and by each line).
• Updated $eval() method for mighty_component_rendered to print evaluated code to the console using zephyr verbosity_level option to suppress it. This was part of a previous iteration on the test development, but I liked it so much I wanted to keep it.
• Fixed legacy mentions of standards
• Fixed legacy use of .self in examples

Testing

• All code have unit tests
• New unit tests for mighty_component_test that checks if the workflow and coverage checks work. Snapshots for tracking the development in code coverage with the printing method.
• Updated tests for the dummy standard components to validate the general workflow.

Checklist

• Code changes have been tested
• Documentation has been updated, if applicable
• All automated tests pass
• Coding style and naming conventions have been followed
• The PR is ready for review and merge

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[github-actions]

Code coverage

Name	Coverage (%)
mighty.component	100
R/component.R	100
R/custom_r.R	100
R/mighty_component_rendered.R	100
R/mighty_component_test.R	100
R/mighty_component.R	100
R/standard.R	100
R/utils-validation.R	100
R/validate_component_code.R	100
R/validate_implicit_join.R	100

[github-actions]

Github pages

Review the pkgdown webpage for the PR here