panics in checks: no labels/values printed

[Andreas Fuchs]

I find that code like the following:

package panics

import (
	"testing"
	"github.com/leanovate/gopter"
	"github.com/leanovate/gopter/gen"
	"github.com/leanovate/gopter/prop"
)

func TestPanic(t *testing.T) {
	properties := gopter.NewProperties(nil)
	properties.Property("Will panic", prop.ForAll(
		func(i int) bool {
			if i%2 == 0 {
				panic("hi")
			}
			return true
		},
		gen.Int().WithLabel("number")))
	properties.TestingRun(t)
}

does catch the panic, but while it prints the random seed, it does not print the parameters that resulted in the panic:

Click for output

$ go test -run TestPanic .
! Will panic: Error on property evaluation after 0 passed tests: Check
   paniced: hi goroutine 20 [running]:
runtime/debug.Stack(0xc0000b36e8, 0x130fa80, 0x13ded80)
        /usr/local/Cellar/go/1.11.5/libexec/src/runtime/debug/stack.go:24 +0xa7
github.com/leanovate/gopter.SaveProp.func1.1(0xc0000b3cf0)
        /Users/asf/go/src/github.com/leanovate/gopter/prop.go:19 +0x6e
panic(0x130fa80, 0x13ded80)
        /usr/local/Cellar/go/1.11.5/libexec/src/runtime/panic.go:513 +0x1b9
github.com/antifuchs/o_test.TestPanic.func1(0x0)
        /Users/asf/go/src/github.com/antifuchs/o/ranges_properties_test.go:131
   +0x39
reflect.Value.call(0x130d6c0, 0x13a01f0, 0x13, 0x138a736, 0x4, 0x1643500,
   0x0, 0x0, 0x0, 0x0, ...)
        /usr/local/Cellar/go/1.11.5/libexec/src/reflect/value.go:447 +0x454
reflect.Value.Call(0x130d6c0, 0x13a01f0, 0x13, 0x1643500, 0x0, 0x0,
   0x13898c0, 0x1, 0x1643500)
        /usr/local/Cellar/go/1.11.5/libexec/src/reflect/value.go:308 +0xa4
github.com/leanovate/gopter/prop.checkConditionFunc.func2(0x1643500, 0x0,
   0x0, 0x1643500)
        /Users/asf/go/src/github.com/leanovate/gopter/prop/check_condition_func.go
  :37 +0x5e
github.com/leanovate/gopter/prop.ForAll.func1(0xc00009a560, 0x13a0258)
        /Users/asf/go/src/github.com/leanovate/gopter/prop/forall.go:40 +0x266
github.com/leanovate/gopter.SaveProp.func1(0xc00009a560, 0x0)
        /Users/asf/go/src/github.com/leanovate/gopter/prop.go:24 +0x6c
github.com/leanovate/gopter.Prop.Check.func1(0x0, 0xc000084fd0, 0x1625ca0)
        /Users/asf/go/src/github.com/leanovate/gopter/prop.go:52 +0x155
github.com/leanovate/gopter.(*runner).runWorkers(0xc000089170, 0x0)
        /Users/asf/go/src/github.com/leanovate/gopter/runner.go:49 +0x2d1
github.com/leanovate/gopter.Prop.Check(0xc000084fb0, 0xc000090840,
   0x138be08)
        /Users/asf/go/src/github.com/leanovate/gopter/prop.go:110 +0x194
github.com/leanovate/gopter.(*Properties).Run(0xc000089110, 0x13e0d60,
   0xc00009a520, 0xc00008b1e0)
        /Users/asf/go/src/github.com/leanovate/gopter/properties.go:37 +0xbc
github.com/leanovate/gopter.(*Properties).TestingRun(0xc000089110,
   0xc000116100, 0x0, 0x0, 0x0)
        /Users/asf/go/src/github.com/leanovate/gopter/properties.go:56 +0x137
github.com/antifuchs/o_test.TestPanic(0xc000116100)
        /Users/asf/go/src/github.com/antifuchs/o/ranges_properties_test.go:133
   +0x126
testing.tRunner(0xc000116100, 0x13a01f8)
        /usr/local/Cellar/go/1.11.5/libexec/src/testing/testing.go:827 +0xbf
created by testing.(*T).Run
        /usr/local/Cellar/go/1.11.5/libexec/src/testing/testing.go:878 +0x35c
Elapsed time: 275.319µs

--- FAIL: TestPanic (0.00s)

properties.go:57: failed with initial seed: 1552922262110846000

FAIL

FAIL    github.com/antifuchs/o  0.015s

What I would expect to see is to see the "Labels of the failing property" printed.

To work around this, I hard-code the random seed in the test options and return false at the start of my function if I am interested in the values, but this seems like a thing gopter could & should do automatically, especially as it already captures the panic.

[Bodo Junglas]

There is no an example/test for this case (example_panic_test.go). Also tweaked the console reporter so that in non-verbose mode the error-stack is suppressed.

[Andreas Fuchs]

Just upgraded gopter and can confirm that it works! Thanks for fixing this!