rustkas

rustkas

Property-Based Testing with PropEr, Erlang, and Elixir: Finding a simplified case of inconsistency (page 146)

I noticed that the necessary inconsistence, which describes in an example PropEr framework does not find a discrepancy in the RFC 4180 specification, is far from at once. I was surprised when I ran the property several times and didn’t get the error I was looking for.

$ rebar3 proper
===> Testing prop_csv:prop_roundtrip()
....................................................................................................
OK: Passed 100 test(s).
===>
1/1 properties passed

When I increased the number of tests to 1000, the framework reproduced the necessary use case.

$ rebar3 proper -n 1000
===> Testing prop_csv:prop_roundtrip()
..........................!
Failed: After 27 test(s).
[#{[40,36] => []},#{[40,36] => []}]

Shrinking .......(7 time(s))
[#{[66,65] => []},#{[66,65] => []}]
===>
0/1 properties passed, 1 failed
===> Failed test cases:
prop_csv:prop_roundtrip() -> false

PropEr can help us in it better. As we know about a possible problem we can narrow Size to 1. For this task we can add simplified generator and property-based test:

%%%%%%%%%%%%%%%%%%
%%% Properties %%%
%%%%%%%%%%%%%%%%%%
prop_roundtrip_01() ->
    ?FORALL(Maps,
            csv_source_01(),
            Maps
            =:= bday_csv:decode(
                    bday_csv:encode(Maps))).

%%%%%%%%%%%%%%%%%%
%%% Generators %%%
%%%%%%%%%%%%%%%%%%

csv_source_01() ->
    ?LET(Keys, header(1), list(entry(1, Keys))).

Launching that property we get the expected error has gotten every time:

$ rebar3 proper -d apps/bday/test -p prop_roundtrip_01
===> Linking _build/default/plugins/rebar3_format to _build/test/plugins/rebar3_format
===> Linking _build/default/plugins/katana_code to _build/test/plugins/katana_code
===> Verifying dependencies...
===> Linking _build/default/plugins/covertool to _build/test/plugins/covertool
===> Compiling bday
===> Testing prop_csv:prop_roundtrip_01()
.......!
Failed: After 8 test(s).
[#{[125] => [75,85,50]},#{[125] => []},#{[125] => []}]

Shrinking ......(6 time(s))
[#{[65] => []},#{[65] => []}]
===>
0/1 properties passed, 1 failed
===> Failed test cases:
prop_csv:prop_roundtrip_01() -> false

Where Next?

Popular Pragmatic Bookshelf topics Top

abtin
page 20: … protoc command… I had to additionally run the following go get commands in order to be able to compile protobuf code using go...
New
telemachus
Python Testing With Pytest - Chapter 2, warnings for “unregistered custom marks” While running the smoke tests in Chapter 2, I get these...
New
mikecargal
Title: Hands-On Rust (Chapter 11: prefab) Just played a couple of amulet-less games. With a bit of debugging, I believe that your can_p...
New
Mmm
Hi, build fails on: bracket-lib = “~0.8.1” when running on Mac Mini M1 Rust version 1.5.0: Compiling winit v0.22.2 error[E0308]: mi...
New
alanq
This isn’t directly about the book contents so maybe not the right forum…but in some of the code apps (e.g. turbo/06) it sends a TURBO_ST...
New
swlaschin
The book has the same “Problem space/Solution space” diagram on page 18 as is on page 17. The correct Problem/Solution space diagrams ar...
New
jskubick
I’m running Android Studio “Arctic Fox” 2020.3.1 Patch 2, and I’m embarrassed to admit that I only made it to page 8 before running into ...
New
oaklandgit
Hi, I completed chapter 6 but am getting the following error when running: thread 'main' panicked at 'Failed to load texture: IoError(O...
New
EdBorn
Title: Agile Web Development with Rails 7: (page 70) I am running windows 11 pro with rails 7.0.3 and ruby 3.1.2p20 (2022-04-12 revision...
New
ggerico
I got this error when executing the plot files on macOS Ventura 13.0.1 with Python 3.10.8 and matplotlib 3.6.1: programming_ML/code/03_...
New

Other popular topics Top

PragmaticBookshelf
Learn from the award-winning programming series that inspired the Elixir language, and go on a step-by-step journey through the most impo...
New
AstonJ
Or looking forward to? :nerd_face:
490 12945 266
New
Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
AstonJ
Do the test and post your score :nerd_face: :keyboard: If possible, please add info such as the keyboard you’re using, the layout (Qw...
New
AstonJ
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
New
New
PragmaticBookshelf
Rails 7 completely redefines what it means to produce fantastic user experiences and provides a way to achieve all the benefits of single...
New
New
First poster: bot
zig/http.zig at 7cf2cbb33ef34c1d211135f56d30fe23b6cacd42 · ziglang/zig. General-purpose programming language and toolchain for maintaini...
New
AstonJ
If you’re getting errors like this: psql: error: connection to server on socket “/tmp/.s.PGSQL.5432” failed: No such file or directory ...
New

Sub Categories: