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Make elements test no longer hang at cost of possible false negative #29

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Merged
merged 3 commits into from
Dec 5, 2020
Merged

Make elements test no longer hang at cost of possible false negative #29

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afa882a
Make `elements` test no longer hang at cost of possible false negative
JordanMartinez Nov 16, 2020
380d2b3
Explain why 1000 is used
JordanMartinez Nov 16, 2020
ea39a8c
Provide simpler way of getting deduplicated set of elements
JordanMartinez Nov 17, 2020
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23 changes: 17 additions & 6 deletions test/Main.purs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,10 @@ import Prelude
import Control.Monad.Gen as Gen
import Control.Monad.Gen.Common as GenC
import Control.Monad.Rec.Class (class MonadRec, tailRecM)
import Data.Array as Array
import Data.Bifunctor (bimap)
import Data.Int as Int
import Data.Foldable (foldl)
import Data.NonEmpty (NonEmpty, (:|))
import Data.Tuple (Tuple(..), snd)
import Effect (Effect)
Expand All @@ -32,12 +34,21 @@ main = do
log "`genNonEmpty` should not reduce the remainder size below zero"
one :: NonEmpty Array Int ← Gen.resize (const 0) $ GenC.genNonEmpty (Gen.sized pure)
liftEffect $ assertEqual { actual: one, expected: 0 :| [] }

log "Ensure that `elements` will produce all possible values (tests will hang if this fails)"
_ ← Gen.suchThat (Gen.elements ("A" :| ["B", "C", "D"])) (_ == "A")
_ ← Gen.suchThat (Gen.elements ("A" :| ["B", "C", "D"])) (_ == "B")
_ ← Gen.suchThat (Gen.elements ("A" :| ["B", "C", "D"])) (_ == "C")
_ ← Gen.suchThat (Gen.elements ("A" :| ["B", "C", "D"])) (_ == "D")

log "Ensure that `elements` will produce all possible values (low chance of false negative)"
let testElems = "A" :| ["B", "C", "D"]

-- use `resize` to generate an Array of 1,000 elements
-- to reduce the chance of a false positive.
elems :: Array String <- Gen.resize (\_ -> 1000) (Gen.unfoldable (Gen.elements testElems))

let
-- implement a Set-like value without depending on ordered-collections
-- because that library depends on this one.
actualElems = Array.sort $ Array.nub elems
expectedElems = foldl Array.snoc [] testElems

liftEffect $ assertEqual { actual: actualElems, expected: expectedElems }
pure unit

log "check frequency"
Expand Down