# hspec-golden
[![Build Status](https://travis-ci.org/stackbuilders/hspec-golden.svg?branch=master)](https://travis-ci.org/stackbuilders/hspec-golden)

## Description
Golden tests store the expected output in a separated file. Each time a golden test
is executed the output of the subject under test (SUT) is compared with the
expected output. If the output of the SUT changes then the test will fail until
the expected output is updated.

`hspec-golden` allows you to write golden tests using the popular `hspec`.

## Getting started

You can write golden tests using `defaultGolden` helper:

```haskell
describe "myFunc" $
  it "generates the right output with the right params" $
     let output = show $ myFunc params
       in defaultGolden "myFunc" output
```

The first parameter of `defaultGolden` is the golden file name. I recommend you to use
`show` and `'functionName` (enable `TemplateHaskellQuotes` for the quote) to
always have a unique name for your file. Example: `show 'myFunc == MyModule.myFunc`.
Although, you can name it as you like.

In case your output isn't a `String` you can define your own `Golden` test
using the `Golden` data type:

```haskell
{-# LANGUAGE TemplateHaskellQuotes #-}

import           Test.Hspec
import           Test.Hspec.Golden
import           Data.Text (Text)
import qualified Data.Text.IO as T

myGoldenTest :: String -> Text -> Golden Text
myGoldenTest name actualOutput =
  Golden {
    output = actualOutput,
    encodePretty = prettyText,
    writeToFile = T.writeFile,
    readFromFile = T.readFile,
    testName = name,
    directory = ".myGoldenTestDir",
    failFirstTime = False
  }

describe "myTextFunc" $
  it "generates the right output with the right params" $
     let textOutput = myTextFunc params
       in myGoldenTest (show 'myTextFunc) textOutput
```

## Installing CLI

You can install the `hspec-golden` command line interface (CLI) with `stack`:

```
$ stack install hspec-golden
```

or `cabal`:


```
$ cabal install hspec-golden
```

The CLI is called `hgold`:

```
$ hgold -h

Update your golden files

Usage: hgold [-u|--update [DIR]] [-v|--version]

Available options:
  -u,--update [DIR]        The testing directory where you're dumping your
                           results. (default: ".golden")
  -v,--version             Show version
  -h,--help                Show this help text
```

Update the golden tests under `.golden` directory:

```
$ hgold
```

Update the golden tests under `.myGoldenTest` directory:

```
$ hgold -u .myGoldenTest
```

## Licensing

MIT, see the [LICENSE file](./LICENSE).

## Contributing
Pull requests for modifications to this program are welcome! Fork and open a PR.

If you're looking for a place to start, you may want to check the [open issue](https://github.com/stackbuilders/hspec-golden/issues).