Skip to Main Content
Property-Based Testing with PropEr, Erlang, and Elixir
book

Property-Based Testing with PropEr, Erlang, and Elixir

by Fred Hebert
January 2019
Intermediate to advanced content levelIntermediate to advanced
376 pages
8h 49m
English
Pragmatic Bookshelf
Content preview from Property-Based Testing with PropEr, Erlang, and Elixir

Dividing with ?LETSHRINK

As you use PropEr, you may find yourself stuck with generators creating huge data structures that take a long time to shrink and often don’t give very interesting results back. This often happens when some very low-probability failure is triggered, meaning that the framework had to generate a lot of data to find it, and has limited chances of shrinking things in a significant manner.

Whenever that happens, the ?LETSHRINK([Pattern, ...], [Generator, ...], Expression) is what you need. In practice, we use the generator like this:

 Erlang
 ?LETSHRINK([A,B,C], [​list​(​number​()), ​list​(​number​()), ​list​(​number​())],
  A ++ B ++ C)
 Elixir
 let_shrink([
  a <- list(number()),
  b <- list(number()),
  c <- list(number()) ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

Erlang and OTP in Action

Erlang and OTP in Action

Eric Merritt, Richard Carlsson, Martin Logan
Testing Elixir

Testing Elixir

Andrea Leopardi, Jeffrey Matthias

Publisher Resources

ISBN: 9781680506556Errata Page