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README.md
# Pavlov
[](https://travis-ci.org/sproutapp/pavlov)
[](http://inch-ci.org/github/sproutapp/pavlov)
A BDD framework for your Elixir projects. It's main goal is to provide a rich, expressive syntax for you to develop your unit tests against. Think of it as RSpec's little Elixir-loving brother.
Pavlov is an abstraction built on top of the excellent ExUnit, Elixir's standard testing library, so all of its standard features are still supported.
Here's a short and sweet example of Pavlov in action:
```elixir
defmodule OrderSpec do
use Pavlov.Case, async: true
import Pavlov.Syntax.Expect
describe ".sum" do
context "When the Order has items" do
let :order do
%Order{items: [
{"burger", 10.0}
{"fries", 5.2}
]}
end
it "sums the prices of its items" do
expect Order.sum(order) |> to_eq 15.2
end
end
end
end
```
## Table Of Contents
- [Usage](#usage)
- [Describe and Context](#describe-and-context)
- [Let](#let)
- [Expects syntax](#expects-syntax)
- [Included Matchers](#included-matchers)
- [Callbacks](#callbacks)
- [before(:each)](#beforeeach)
- [before(:all)](#beforeall)
- [Mocking](#mocking)
- [Mocks with arguments](#mocks-with-arguments)
- [Skipping tests](#skipping-tests)
- [xit](#xit)
- [xdescribe/xcontext](#xdescribexcontext)
- [Development](#development)
- [Running the tests](#running-the-tests)
- [Building the docs](#building-the-docs)
- [Contributing](#contributing)
## Usage
Add Pavlov as a dependency in your `mix.exs` file:
```elixir
defp deps do
[{:pavlov, ">= 0.1.0", only: :test}]
end
```
After you are done, run `mix deps.get` in your shell to fetch the dependencies.
To start execution of your Pavlov tests, add the following to your 'test/test_helper.exs':
```elixir
Pavlov.start
```
Afterwards, running `mix test` in your shell will run all test suites.
## Describe and Context
You may use the `describe` and `context` constructs to group tests together in a logical way. Although `context` is just an alias for `describe`, you may use it to add some extra meaning to your tests, ie. you can use `contexts` within a `described` module function to simulate different conditions under which your function should work.
## Let
You can use `let` to define memoized helper methods for your tests. The returning value is cached across all invocations. 'let' is lazily-evaluated, meaning that its body is not evaluated until the first time the method is invoked.
```elixir
let :order do
%Order{items: [
{"burger", 10.0}
{"fries", 5.2}
]}
end
```
## Expects syntax
You may use the regular ExUnit `assert` syntax if you wish, but Pavlov includes
an `expect` syntax that makes your tests more readable.
If you wish to use this syntax, simply import the `Pavlov.Syntax.Expect` at the
beginning of your Test module:
```elixir
defmodule MyTest do
use Pavlov.Case, async: true
import Pavlov.Syntax.Expect
#...
end
```
All core matchers are supported under both syntaxes.
## Included Matchers
When using the `expects` syntax, all matchers have negative counterparts, ie:
```elixir
expect 1 |> not_to_eq 2
expect(1 > 5) |> not_to_be_true
```
Visit the [Pavlov Wiki](https://github.com/sproutapp/pavlov/wiki/Included-Matchers)
to learn more about all of the core matchers available for your tests.
## Callbacks
For now, Pavlov only supports callbacks that run before test cases. [ExUnit's
`on_exit` callback](http://elixir-lang.org/docs/stable/ex_unit/ExUnit.Callbacks.html#on_exit/2) is still fully supported though, and may be used normally inside your `before` callbacks.
### before(:each)
Runs the specified code before every test case.
```elixir
describe "before :each" do
before :each do
IO.puts "A test is about to start"
:ok
end
it "does something" do
#...
end
it "does something else" do
#...
end
end
```
In this case, `"A test is about to start"` is printed twice to the console.
### before(:all)
Runs the specified code once before any tests run.
```elixir
describe "before :all" do
before :all do
IO.puts "This suite is about to run"
:ok
end
it "does something" do
#...
end
it "does something else" do
#...
end
end
```
In this case, `"This suite is about to run"` is printed once to the console.
## Mocking
Pavlov provides facilities to mock functions in your Elixir modules. This is
achieved using [Meck](https://github.com/eproxus/meck), an erlang mocking tool.
Here's a simple example using [HTTPotion](https://github.com/myfreeweb/httpotion):
```elixir
before :each do
allow HTTPotion |> to_receive(get: fn(url) -> "<html></html>" end)
end
it "gets a page" do
result = HTTPotion.get("http://example.com")
expect HTTPotion |> to_have_received :get
expect result |> to_eq "<html></html>"
end
```
If you want the mock to retain all other functions in the original module,
then you will need to pass the `opts` `List` argument to the `allow` function
and include the `:passthrough` value. The `allow` function specifies a default
`opts` `List` that includes the `:no_link` value. This value should be included
in the `List` as it ensures that the mock (which is linked to the creating
process) will unload automatically when a crash occurs.
```elixir
before :each do
allow(HTTPotion, [:no_link, :passthrough]) |> to_receive(get: fn(url) -> "<html></html>" end)
end
```
Expectations on mocks also work using `asserts` syntax via the `called` matcher:
```elixir
before :each do
allow HTTPotion |> to_receive(get: fn(url) -> "<html></html>" end)
end
it "gets a page" do
HTTPotion.get("http://example.com")
assert called HTTPotion.get
end
```
### Mocks with arguments
You can also perform assertions on what arguments were passed to a mocked
method:
```elixir
before :each do
allow HTTPotion |> to_receive(get: fn(url) -> "<html></html>" end)
end
it "gets a page" do
HTTPotion.get("http://example.com")
expect HTTPotion |> to_have_received :get |> with "http://example.com"
end
```
In `asserts` syntax:
```elixir
before :each do
allow HTTPotion |> to_receive (get: fn(url) -> url end )
end
it "gets a page" do
HTTPotion.get("http://example.com")
assert called HTTPotion.get("http://example.com")
end
```
## Skipping tests
Pavlov runs with the `--exclude pending:true` configuration by default, which
means that tests tagged with `:pending` will not be run.
Pavlov offers several convenience methods to skip your tests, BDD style:
### xit
Marks a specific test as pending and will not run it.
```elixir
xit "does not run" do
# This will never run
end
```
### xdescribe/xcontext
Marks a group of tests as pending and will not run them. Just as `describe`
and `context`, `xdescribe` and `xcontext` are analogous.
```elixir
xdescribe "A pending group" do
it "does not run" do
# This will never run
end
it "does not run either" do
# This will never run either
end
end
```
## Development
After cloning the repo, make sure to download all dependencies using `mix deps.get`.
Pavlov is tested using Pavlov itself, so the general philosophy is to simply write a test using a given feature until it passes.
### Running the tests
Simply run `mix test`
### Building the docs
Run `MIX_ENV=docs mix docs`. The resulting HTML files will be output to the `docs` folder.
## Contributing
1. Fork it ( https://github.com/sproutapp/pavlov/fork )
2. Create your feature branch (`git checkout -b my-new-feature`)
3. Commit your changes (`git commit -am 'Add some feature'`)
4. Push to the branch (`git push origin my-new-feature`)
5. Create a new Pull Request