# Tracee
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This Elixir library offers functionality to trace and assert expected function
calls within concurrent Elixir processes.
This allows you to ensure that destructive and/or expensive functions are only
called the expected number of times. For more information, see [the Elixir forum
post](https://elixirforum.com/t/tracing-and-asserting-function-calls/63035) that
motivated the development of this library.
## Installation
Just add `tracee` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[
{:tracee, "~> 0.2.0", only: :test}
]
end
```
## Usage
```elixir
defmodule ModuleTest do
use ExUnit.Case
import Tracee
setup :verify_on_exit!
describe "fun/0" do
test "calls expensive function only once" do
expect(AnotherModule, :expensive_fun, 1)
assert Module.fun()
end
test "calls expensive function only once from another process" do
expect(AnotherModule, :expensive_fun, 1)
assert fn -> Module.fun() end
|> Task.async()
|> Task.await()
end
test "never calls expensive function" do
expect(AnotherModule, :expensive_fun, 1, 0)
assert Module.fun()
end
end
end
```
## License
[MIT](./LICENSE)