Add a set of "chaos monkey" tests for rehydration. #991
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Some ideas that @krisselden just mentioned to me in DM:
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is this still a WIP? |
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Thanks for the reminder @krisselden, rebased and updated. Should be good to land once green. |
This adds tests that run a number of iterations removing a random node, and confirming that the final rehydrated (e.g. client rendered) HTML is correct. In order to make these tests actionable the infrastructure added here provides a way to replicate _specific_ iterations upon failure. The way this works is based on QUnit's internal `QUnit.config.seed` implementation. When a `QUnit` test suite is ran with the `seed` query param set (with no value e.g. `/tests/index.html?hidepassed&seed`), QUnit will choose a random seed and use that seed to choose a randomized test order. Then if a failure occurs with the randomized and seeded test run, you can run the tests again with **exactly** that seed value by specifying the `seed` query param _with_ the failing seed value (e.g. `/tests/index.html?hidepassed&seed=THEVALUEHERE`). The implementation here piggie backs on that system to use the QUnit's seed value (along with a copied version of their [hashing function](qunitjs/qunit:src/core/utilities.js@2.9.3#L144-L158) and [seeded randomizer](qunitjs/qunit:src/core/processing-queue.js@2.9.3#L134-L154)) in addition to the iteration being ran to always select a "known value" to remove. This means that given the correct seed (and iteration number) we can easily replicate **specific** failure scenarios without manually having to track it down. The way you'd do this is: 1. Run the tests with `/tests/index.html?hidepassed&seed` until a failure occurs. 2. Look at the failed tests assertion, grab the rerun URL printed in the failed assertion. 3. Run the tests again with that set of query params (e.g. `/tests/index.html?hidepassed&seed=SEED_HERE&iteration=ITERATION_HERE`).
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Based on an idea that @krisselden and I had while working on #988 this adds tests that run a number of iterations removing a random node, and confirming that the final rehydrated (e.g. client rendered) HTML is correct.
In order to make these tests actionable the infrastructure added here provides a way to replicate specific iterations upon failure. The way this works is based on QUnit's internal
QUnit.config.seedimplementation. When aQUnittest suite is ran with theseedquery param set (with no value e.g./tests/index.html?hidepassed&seed), QUnit will choose a random seed and use that seed to choose a randomized test order. Then if a failure occurs with the randomized and seeded test run, you can run the tests again with exactly that seed value byspecifying the
seedquery param with the failing seed value (e.g./tests/index.html?hidepassed&seed=THEVALUEHERE). The implementation here piggie backs on that system to use the QUnit's seed value (along with a copied version of their hashing functionand seeded randomizer) in addition to the iteration being ran to always select a "known value" to remove. This means that given the correct seed (and iteration number) we can easily replicate specific failure scenarios without manually having to track it down.
The way you'd do this is:
/tests/index.html?hidepassed&seeduntil a failure occurs./tests/index.html?hidepassed&seed=SEED_HERE&iteration=ITERATION_HERE).Currently includes the changes from #988, but will rebase once that lands.