Add Shrink.suchThat #484
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Add Shrink.suchThat #484
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koterpillar
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ashawley
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Mar 2, 2020
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This is a nice contribution. I don't have any objection. It helps improve a correspondence in the APIs of generators and shrinks. If we can just fix the strange commits to the README, this looks good to me. |
ashawley
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Mar 2, 2020
ashawley
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Mar 11, 2020
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| /** Shrink a list, maintaining even length */ | ||
| val shrinkEvenList: Shrink[List[Int]] = | ||
| implicitly[Shrink[List[Int]]].suchThat(_.length % 2 == 0) |
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Is it possible to make shrinkEvenList implicit? Even if I make it lazy, I get an infinite loop when I use it in a property test.
In your test, you use the explicit shrink version of forAll. Unfortunately, that only works for single arity forAll.
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Please review #644 when you get a chance, thanks.
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When using
Gen.suchThator generators that maintain invariants by construction, shrinking can break those invariants. AddShrink.suchThatto ensure no invalid values are shrunk to.