PROPERTY TESTING?

WHAT IS

property

? counter-example ?

something always true

λ> quickCheck $ \(x :: Integer) -> x === 1
*** Failed! Falsified (after 1 test):  
x: 0
0 /= 1

λ> quickCheck $ \(xs :: [Char]) -> length xs === 0
*** Failed! Falsified (after 3 tests and 2 shrinks):    
xs: "a" 
1 /= 0

λ> quickCheck $ \(x :: Integer) (y :: Integer) -> x /= 0 ==> y+x =/= y*x
+++ OK, passed 100 tests; 12 discarded.

λ> quickCheck $ \(x :: Integer) (y :: Integer) -> x /= 0 ==> y+x =/= y*x
*** Failed! Falsified (after 3 tests):                  
x: 2
y: 2
4 == 4

\forall x \in \N. x = 1

\forall xs \in \alpha^*. length(xs) = 0

\forall (x,y) \in \N\times\N. x \ne 0 \implies x+y \ne x*y

sort :: [x] -> [x]

length(xs) = length(sort(xs))

sort(sort(xs)) = sort(xs)

sort(xs) = xs

!

assert (sort [] == [])
assert (sort [2,1] == [1,2])
assert (sort [1,2,1] == [1,1,2])

Generating

Labelling

Simplifying

Generating...

(random) data from composable primitives.

Simplifying...

complex data structures down to "minimal" counter-examples.

Labelling...

properties to measure coverage and efficiency.

GREAT TEST RUNNER

HOW TO

FIND PROPERTIES

Idempotence

Oracles

?

Labyrinth

Roundtrips

SMART

CONTRACTS

state 0

state 1

state 2

validator

redeemer

O.K.

K.O.

Example: Authentication Badges

$A, $B, ...

main redeemer

42 ₳, 1 $A

14 ₳, 1M $HOSKY, 1 $B

CHAOS

ENGINEERING

Chaos engineering is the discipline of experimenting on a system in order to build confidence in the system's capability to withstand turbulent conditions in production.

inputs

reference inputs

redeemers

witnesses

transaction

??

Bespoke to the contract

Allow for building

sequences of transactions

Classify failures

validator logic

FIRST BUG

prop_check_badges_ok

_ada

badge

..

counterexample

SECOND BUG

prop_check_badges_ko

badge??

LIMITS

AND UGLY STUFF

It can be slow...

but!

It's only when simplifying counterexamples
New VM coming with 10x perf
It frees up time for coffee!

finding bugs

Transactions carry noise...

inputs

reference inputs

validity range

outputs, fees, mint, certificates, withdrawals

redeemers, datums, signatories, id, votes, gov actions, ...

but!

It's still better than raw CBOR...

Failing scenarii must be thought of...

but!

You'll get generators wrong... creating interesting scenarii.
It's re-usable and uses 'transaction' as an interface.
You get a free specification for auditors as an outcome!
It's actually fun*.

* for some definition of fun

I lied to you (a little)

but!

No but, it's just ugly.

WHAT NOW

?

It's Open Source!

https://github.com/aiken-lang/fuzz.git