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https://gerrit.wikimedia.org/r/mediawiki/extensions/MultimediaViewer
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This test was leaving behind the black overlay, obscuring the test results interface. Upon closer inspection, it appears not one part of this test is doing anything that actually works. * Assertion 1: `viewer.isOpen === false` This is the initial and default state. Not essential for the test, but so far so good. * Prep for Assertion 2 & 3: We call loadImageByTitle. One might think that this will set isOpen to true, but, this isn't asserted. If one did, the test would fail, because loadImageByTitle returns early from its first branch in `!this.thumbs.length` and is thus a no-op, and adds nothing to the test. We set `location.hash = 'Foo'`. * Assertion 2: `location.hash === '#Foo'` Assertion 3: `viewer.isOpen === false` Assertion 2 is meaningless because handling of hash changes appears to be asynchronous. Perhaps not always, but at least the indirection used in this codebase makes it async. Hence, the fact that it is correctly normalised to '#Foo' is meaningless as the popstate and hashchange event handler haven't been processed yet. If they were, it would still be meaningless since viewer.isOpen was never true in the first place and MMV's event handlers for popstate/hashchange are guarded by `isOpen`. * Prep for Assertion 4: location.hash = Bar * Assertion 4: `location.hash === '#Bar'` Idem. * Prep for Assertion 5: Replace the viewer.loadImageByTitle function with a function that performs a nested assertion. This function is never called and its assertion never reached. This is a textbook example why assertions should never be nested. If you rewrite this in following with the advice from <https://api.qunitjs.com/assert/verifySteps/>, we find that the array is in fact empty by the end of the test() function. ```js var seen = []; viewer.loadImageByTitle = function ( title ) { // assert.strictEqual( … ); seen.push( title.getPrefixedText() ); }; location.hash = …; location.hash = …; location.hash = …; location.hash = …; assert.deepEqual( seen, [ 'File:' + imageSrc' } ); // Actual: [] ``` == Misc notes == The test ends with "#/media/File:Foo bar.jpg" set on location.hash, and the black overlay covering the page. It seems that the hashchange are async, and that the first in a given event loop tick "wins", with later ones being ignored. Observing this with debugger/breakpoints is hard given that each pause results in the effect not being observable. console.log(location.href) at the end of the test shows hash='#', but placing a debugger at the end of the test results in the hash being "#/media/…" instead. Exprienced in Firefox 117 on macOS. Change-Id: Ib37bec1b3e67fcab1da89d23381a3adbb6312827 |
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