cheatsheets/exunit.md

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---
title: ExUnit
category: Elixir
updated: 2018-11-19
---
### Test cases
```elixir
defmodule MyTest do
use ExUnit.Case
use ExUnit.Case, async: true # for async
test "the truth" do
assert 1 + 1 == 2
end
end
```
### Capture IO
```elixir
import ExUnit.CaptureIO
test "capture io" do
result = capture_io(fn ->
IO.puts "sup"
end)
assert result == "sup\n"
end
```
### Capture logs
```elixir
config :ex_unit, capture_logs: true
```
### Async
```elixir
defmodule AssertionTest do
# run concurrently with other test cases
use ExUnit.Case, async: true
end
```
### Assertions
```elixir
assert x == y
refute x == y
assert_raise ArithmeticError, fn ->
1 + "test"
end
assert_raise ArithmeticError, "message", fn -> ...
assert_raise ArithmeticError, ~r/message/, fn -> ...
flunk "This should've been an error"
```
See: [Assertions](http://devdocs.io/elixir/ex_unit/exunit.assertions)
## Setup
### Pattern matching
```elixir
setup do
{:ok, name: "John"}
end
```
```elixir
test "it works", %{name: name} do
assert name == "John"
end
```
### Setup
```elixir
defp my_hook(_context) do
# Invoked in every block in "a block"
{:ok, name: "John", age: 54}
end
describe "a block" do
setup [:my_hook]
test "John's age", context do
assert context[:name] == "John"
assert context[:age] == 54
end
end
```
## Also see
{: .-one-column}
* [ExUnit Docs](http://devdocs.io/elixir/ex_unit/exunit#configure/1)