StreamData

What StreamData is

StreamData is an Elixir library for generating data and writing property-based tests with ExUnit. It supplies generators that you can combine into custom generators, and those generators also work as streams of random data through Elixir’s Enumerable protocol. Its ExUnitProperties module runs properties with generated inputs to look for cases that disprove expected behavior. When a generated value causes a failure, StreamData can shrink it toward a simpler example, which can make the failure easier to understand and reproduce. Reusing the seed from the failing run lets you reproduce it; the library does not store counter-examples in a file. StreamData is written entirely in Elixir and provides an idiomatic Elixir API. The project recommends adding it as a dependency in the test environment, where it can support tests and test-data generation. To install it, add the `stream_data` dependency and run `mix deps.get`. It is free under the Apache License 2.0, and online documentation is available through HexDocs. StreamData does not support stateful property-based testing.

Who it suits

StreamData suits Elixir developers who use ExUnit and want to generate inputs for property-based tests or test data. It is also useful when a failing generated value needs to be reduced to a simpler example and reproduced with its seed.

Limits

StreamData does not support stateful property-based testing and does not store counter-examples in a file.

Getting started

1. Open the StreamData repository on GitHub.
2. Add `stream_data` as a dependency in the test environment.
3. Run `mix deps.get`.
4. Read the online documentation on HexDocs.

Verdict

Choose StreamData if you write Elixir tests with ExUnit and want generated inputs, shrinking, and reproducible failures. Look elsewhere if your property-based tests need stateful testing or saved counter-examples.