Replace Zeus with process forking strategy #271
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We specifically want test negative `raise_error` expectations, which is normally a no-no in RSpec.
This should maintain the speedup that Zeus provided by doing effectively the same thing, namely avoiding the startup cost of loading frameworks like RSpec and Rails by loading before fork. This may make it impossible to develop on Windows without further treatment.
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📖 A new version of the docsite has been published at: https://splitwise.github.io/super_diff/branches/speed-up-integration-tests/91fe143eff6806c708e5a0eb5931c4b915b87673 |
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📖 A new version of the docsite has been published at: https://splitwise.github.io/super_diff/branches/speed-up-integration-tests/58705a1a40e5321fdb8f054a98cdb5b83e20e3e0 |
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📖 A new version of the docsite has been published at: https://splitwise.github.io/super_diff/branches/speed-up-integration-tests/ec7a32f9770134896c58117080a6774d39817439 |
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📖 A new version of the docsite has been published at: https://splitwise.github.io/super_diff/branches/speed-up-integration-tests/9a15b48e838ecd770d3df92a5c58a5ba4e8ad889 |
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📖 A new version of the docsite has been published at: https://splitwise.github.io/super_diff/branches/speed-up-integration-tests/ad73d2824ce3772918c7f61db23dae630e71e554 |
Summary
Integration tests without Zeus are very slow because we run each example in a new process, which has to load all dependencies and frameworks – like RSpec, SuperDiff, ActiveSupport, etc – from scratch.
Zeus improved on this, but has a client-server architecture and has been proving somewhat difficult to use. If we instead load the dependencies and then run RSpec in a new forked subprocess, we don't have to reload anything loaded before fork time, and don't have to use Zeus.
Performance
Run on a 10-core Apple M1 Pro with 16 GB RAM.
Bench:
Before
387.17s user 146.91s system 95% cpu 9:18.77 total
After
88.45s user 21.43s system 97% cpu 1:52.32 total
This represents a ~5x speed-up.