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Add replay hint to failure message #720

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Merged
merged 1 commit into from
Nov 9, 2025
Merged

Add replay hint to failure message #720

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9 changes: 6 additions & 3 deletions src/FsCheck/Runner.fs
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Original file line number Diff line number Diff line change
Expand Up @@ -499,9 +499,12 @@ module Runner =
| 1 -> sprintf "Label of failing property: %s%s" (labelsToString l) newline
| _ -> sprintf "Labels of failing property (one or more is failing):%s%s%s" newline (labelsToString l) newline

let onFailureToString name data originalArgs args usedSeed lastSeed lastSize =
sprintf "%sFalsifiable, after %i test%s (%i shrink%s) (%A)%sLast step was invoked with size of %i and seed of (%A):%s"
name data.NumberOfTests (pluralize data.NumberOfTests) data.NumberOfShrinks (pluralize data.NumberOfShrinks) usedSeed newline lastSize lastSeed newline
let onFailureToString name data originalArgs args usedSeed (lastSeed:Rnd) lastSize =
let replayHint =
if data.NumberOfTests > 1 then $".%s{newline}Replay directly at failing step with (%d{lastSeed.Seed},%d{lastSeed.Gamma},%d{lastSize})."
else ":"

$"%s{name}Falsifiable, after %i{data.NumberOfTests} test%s{pluralize data.NumberOfTests} (%i{data.NumberOfShrinks} shrink%s{pluralize data.NumberOfShrinks}) (%A{usedSeed}). %s{newline}Last step was invoked with size of %i{lastSize} and seed of (%A{lastSeed})%s{replayHint}%s{newline}"
+ maybePrintLabels data.Labels
+ sprintf "Original:%s%s%s" newline (argumentsToString originalArgs) newline
+ if (data.NumberOfShrinks > 0 ) then sprintf "Shrunk:%s%s%s" newline (argumentsToString args) newline else ""
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