Write tests

[cyyynthia]

Not sure what the best strategy would be here...

[mary-ext]

We can move the transformations out of the load hook so that we can do snapshot tests of the resulting SVG and JS code, that should be good for a start.

After that we can move on to browser screenshot testing, to make it easier to see if the SVGs are being shown correctly

[cyyynthia]

Sounds good to me. https://playwright.dev/docs/test-snapshots should be the most appropriate tool for the screenshot job; Ideally all browsers should have a very similar output but I don't know if the difference between render engines will require using different screenshots to compare.

Points to test are:

• Width/Height preservation, if enabled (unit)
• Width/Height configuration, if enabled (unit)
• Behavior when both of the above are enabled (unit)
• ViewBox restoration, if enabled (unit)
• Fill/Stroke replacement, if enabled (unit)
  • none should never be replaced
• The generated code should work (visual)
• Correct processing of referenced resources within the SVG
  • image, use, ...
  • The generated SVG should be visually identical to the source SVG
• All targets render the same (happydom/jsdom should be enough for this one)