# `ExFuzz`
[🔗](https://github.com/Snehil-Shah/ex_fuzz/blob/v0.1.0/lib/ex_fuzz.ex#L1)

Coverage-guided fuzz testing for Elixir.

    defmodule JasonTest do
      use ExUnit.Case
      use ExFuzz

      @tag timeout: 100
      fuzz "Jason never crashes", data <- binary(), seeds: ["{}", "[1]"] do
        with {:ok, term} <- Jason.decode(data) do
          assert Jason.decode!(Jason.encode!(term)) == term
        end
      end
    end

Fuzz tests run alongside your regular ExUnit tests,
using the seed corpus as an ever-growing regression suite.
Run only them with `mix test --only fuzz`.

To start fuzzing a target, point `mix fuzz` at the test by line or name:

    $ mix fuzz test/jason_test.exs:6
    $ mix fuzz test/jason_test.exs:"fuzz Jason never crashes"

Failing inputs are saved as seed corpus to `test/fixtures/fuzz/` and replayed by `mix test` from then on.
You can configure this with `:corpus_dir` under the `:ex_fuzz` key of your project config.

# `fuzz`
*macro* 

Defines a fuzz test with `message`, running its body as the target, once per input.

The test may also define a pattern, which will be matched against the test context.

## Options

  * `:seeds` - example inputs that fuzzing starts from, part of the seed corpus.

## Examples

    fuzz "Jason never crashes", data <- binary(), seeds: ["{}", "[1]"] do
      with {:ok, term} <- Jason.decode(data) do
        assert Jason.decode!(Jason.encode!(term)) == term
      end
    end

You can start fuzzing the target using `mix fuzz`:

    $ mix fuzz test/jason_test.exs:"fuzz Jason never crashes"

---

*Consult [api-reference.md](api-reference.md) for complete listing*