rewire
===
[](https://travis-ci.org/stephanos/rewire)
[](https://hex.pm/packages/rewire)
Keep your code free from dependency injection and mocking concerns by using `rewire` in your unit tests to stub out any module dependencies.
## Usage
For example, given this module:
```elixir
defmodule Conversation do
def init(), do: English.greet() # the dependency is hard-wired
end
```
You can rewire the dependency with a `mox`-based mock like this:
```elixir
defmodule MyTest do
use ExUnit.Case
use Rewire
import Mox
rewire Conversation, English: Mock # acts as an alias to the rewired module
test "greet" do
stub(Mock, :greet, fn -> "bonjour" end)
assert Conversation.init() == "bonjour" # this uses Mock now!
end
end
```
Alternatively, you can also rewire a module on a test-by-test basis:
```elixir
defmodule MyTest do
use ExUnit.Case
use Rewire
import Mox
test "greet" do
rewire Conversation, English: Mock do # within the block it is rewired
stub(Mock, :greet, fn -> "bonjour" end)
assert Conversation.init() == "bonjour" # this uses Mock now!
end
end
end
```
## FAQ
**Witchcraft! How does this work??**
Simply put, `rewire` will create a copy of the module to rewire under a new name, replacing all hard-coded module references that should be changed in the process. Plus, it rewrites the test code in the `rewire` block to use the generated module instead.
**Will that slow down my tests?**
Possibly just a little? Conclusive data isn't in yet.
**Does it work with `mox`?**
It works great with [mox](https://github.com/dashbitco/mox) since `rewire` doesn't care about where the replacement module comes from. `rewire` and `mox` are a great pair!
