T/51: Used config.initialData instead of innerHTML to set the initial state of the editor

[oleq]

Suggested merge commit message (convention)

Internal: Used config.initialData instead of innerHTML to set the initial state of the editor. Closes #51.

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Additional information

Nuke the node_modules before running tests. The newer build-classic is required to support initialData.

[coveralls]

Pull Request Test Coverage Report for Build 85

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 83:	0.0%
Covered Lines:	30
Relevant Lines:	30

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💛 - Coveralls

[ma2ciek]

I see that now there're such warnings on CI:

ERROR: '[vue-test-utils]: Global error handler detected (Vue.config.errorHandler). 
Vue Test Utils sets a custom error handler to throw errors thrown by instances. If you want this behavior in your tests, you must remove the global error handler.'

Are they correct?
Can we somehow remove them?

[oleq]

They are incorrect. Or not very accurate. Because tests use Vue.nextTick, things are asynchronous and done() is used in places like this https://github.com/ckeditor/ckeditor5-vue/blob/t/51/tests/ckeditor.js#L50 in the past.

I added Vue.config.errorHandler = done; in all tests as recommended in the official guide to improve readability of errors.

Before:

After:

It helps a lot but for some reason, vue-tests-utils displays an error (which kinda contradicts their documentation...). Maybe this is because vue-tests-utils is still beta (?). Anyway, it's not changing anything but DX so we can either remove the Vue.config.errorHandler = done; line and live with ugly Mocha errors or just live with quirky errors from vue-tests-utils.

[oleq]

What about the PR itself? Does it make sense?

[ma2ciek]

Overall the PR is good and the change makes sense, I'm merging it.