# Power Assert
[](https://hex.pm/packages/power_assert) [](https://hex.pm/packages/power_assert) [](https://travis-ci.org/ma2gedev/power_assert_ex) [](http://www.apache.org/licenses/LICENSE-2.0)
Power Assert for Elixir.
Example test is here:
```elixir
test "Enum.at should return the element at the given index" do
array = [1, 2, 3, 4, 5, 6]; index = 2; two = 2
assert array |> Enum.at(index) == two
end
```
And the result is like the following:
```
1) test Enum.at should return the element at the given index (PowerAssertTest)
array |> Enum.at(index) == two
| | | |
| 3 2 2
[1, 2, 3, 4, 5, 6]
```
Enjoy :muscle: !
## Dependencies
- ExUnit
## Installation
```
# add dependencies in mix.exs
defp deps do
[
{:power_assert, "~> 0.0.7"}
]
end
# and fetch
$ mix deps.get
```
## How to use
```elixir
# replace `use ExUnit.Case` into `use PowerAssert` in your test code
## before
defmodule YourAwesomeTest do
use ExUnit.Case # <-- **HERE**
end
## after
defmodule YourAwesomeTest do
use PowerAssert # <-- **REPLACED**
end
```
when ExUnit.CaseTemplate
```elixir
# replace `use ExUnit.CaseTemplate` into `use PowerAssert.CaseTemplate` in your test code
## before
defmodule YourAwesomeTest do
use ExUnit.CaseTemplate # <-- **HERE**
end
## after
defmodule YourAwesomeTest do
use PowerAssert.CaseTemplate # <-- **REPLACED**
end
```
useful command to replace `use ExUnit.CaseTemplate` and `use ExUnit.Case`
```bash
$ git grep -l 'use ExUnit\.CaseTemplate' | xargs sed -i.bak -e 's/use ExUnit\.CaseTemplate/use PowerAssert.CaseTemplate/g'
$ git grep -l 'use ExUnit\.Case' | xargs sed -i.bak -e 's/use ExUnit\.Case/use PowerAssert/g'
```
## How to use other framework depending on ExUnit such as ExSpec
For instance ExSpec calls `use ExUnit` inside module, `assert` macro is already imported and conflicted with our `assert` macro.
So avoiding conflicted problem we provide the `:use_ex_unit` option:
If `:use_ex_unit` is set as `true`, `use PowerAssert` provides `power_assert` macro instead of `assert`. Also does not `use ExUnit.Case` inside module.
NOTE: This option is available experimentally.
```
defmodule ExSpecBasedTest do
use ExSpec
use PowerAssert, use_ex_unit: true # use PowerAssert with :use_ex_unit option
describe "describe" do
it "it" do
power_assert something == "hoge" # `power_assert` macro is enabled
end
end
end
```
## API
```
assert(expression, message \\ nil)
```
## TODO
- [x] `ExUnit.CaseTemplate` with `using function`
- [x] support `assert [one] = [two]`
- currently rely on `ExUnit.Assertions.assert/1`
- and more we've not yet noticed
## Limitation
- NOT SUPPORTED
- match expression ex: `assert List.first(x = [false])`
- fn expression ex: `assert fn(x) -> x == 1 end.(2)`
- :: expression ex: `<< x :: bitstring >>`
- this means string interpolations also unsupported ex: `"#{x} hoge"`
- sigil expression ex: `~w(hoge fuga)`
- quote arguments ex: `assert quote(@opts, do: :hoge)`
- case expression
- get_and_update_in/2, put_in/2, update_in/2, for/1
- <<>> expression includes attributes `<<@x, "y">>; <<x :: binary, "y">>`
- `__MODULE__.Foo`
- many macros maybe caught error...
## Resources
- [Power Assert Inside in Elixir](https://speakerdeck.com/ma2gedev/power-assert-inside-in-elixir)
## License
Distributed under the Apache 2 License.
Check [LICENSE](LICENSE) files for more information.
