Efficient falseToFailure

CHANGELOG.md

@@ -1,3 +1,9 @@
+## Version 0.14.0
+- No longer targeting .NET Framework ([#417][417], [@LyndonGingerich][LyndonGingerich])
+- The runtime of `Property.recheck` is now about the same as `Property.check`.  Previously, it was about ten times slower. ([#433][433], [@TysonMN][TysonMN])
+- The error message given when a deadend is reached during rechecking is improved to say that the cause is a change in generators. ([#436][436], [@TysonMN][TysonMN])
+- The implementation of `Property.falseToFailure` is now better.  As a result, `Property.recheckBool` now only tests the shrunken input. ([#437][437], [@TysonMN][TysonMN])
+
 ## Version 0.13.0 (2022-07-23)
 
 - Fix bug in `Property.recheck` where the result is always `Failed`. ([#415][415], [@TysonMN][TysonMN])
@@ -199,6 +205,12 @@
 [LyndonGingerich]
   https://github.com/LyndonGingerich
 
+[436]:
+  https://github.com/hedgehogqa/fsharp-hedgehog/pull/436
+[433]:
+  https://github.com/hedgehogqa/fsharp-hedgehog/pull/433
+[417]:
+  https://github.com/hedgehogqa/fsharp-hedgehog/pull/417
 [416]:
   https://github.com/hedgehogqa/fsharp-hedgehog/pull/416
 [415]:

src/Hedgehog/Property.fs

@@ -2,6 +2,9 @@ namespace Hedgehog
 
 open System
 
+type internal TestReturnedFalseException() =
+  inherit System.Exception("Expected 'true' but was 'false'.")
+
 
 [<Struct>]
 type Property<'a> =
@@ -95,7 +98,7 @@ module Property =
         |> ofGen
 
     let falseToFailure p =
-        p |> bind ofBool
+        p |> map (fun b -> if not b then raise (TestReturnedFalseException()))
 
     let internal printValue (value) : string =
         // sprintf "%A" is not prepared for printing ResizeArray<_> (C# List<T>) so we prepare the value instead

tests/Hedgehog.Tests/PropertyTests.fs

@@ -94,6 +94,34 @@ let propertyTests = testList "Property tests" [
                 //render.Contains "actual: 1" =! true // comment out for now since it causes the Fable test to fail
 
 
+    testCase "recheckBool only tests shrunken input" <| fun () ->
+        let mutable count = 0
+        let prop =
+            property {
+                let! i = Range.constant 0 1_000_000 |> Gen.int32
+                count <- count + 1
+                return i = 0
+            }
+
+        let report1 = Property.reportBool prop
+        match report1.Status with
+        | OK -> failwith "Initial report should be Failed, not OK"
+        | GaveUp -> failwith "Initial report should be Failed, not GaveUp"
+        | Failed failure1 ->
+            count <- 0
+            let report2 =
+                Property.reportRecheckBool
+                    (RecheckData.serialize failure1.RecheckInfo.Value.Data)
+                    prop
+            match report2.Status with
+            | OK -> failwith "Recheck report should be Failed, not OK"
+            | GaveUp -> failwith "Recheck report should be Failed, not GaveUp"
+            | Failed _ ->
+                let render = Report.render report2
+                count =! 1
+                //render.Contains "actual: 1" =! true // comment out for now since it causes the Fable test to fail
+
+
     testCase "recheck passes after code is fixed" <| fun () ->
         let mutable b = false
         let prop =
@@ -151,5 +179,4 @@ let propertyTests = testList "Property tests" [
                   .Replace(")", "")
 
         actual =! "1,0"
-
 ]