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A Haskell client for the Selenium WebDriver protocol.

README.md

hs-webdriver is a Selenium WebDriver client for the Haskell programming language. You can use it to automate browser sessions for testing, system administration, etc.

For more information about Selenium itself, see http://seleniumhq.org/

Contents

Installation

hs-webdriver uses the Cabal build system to configure, build, install, and generate documentation on multiple platforms.

For more information on using Cabal and its various installation options, see the Cabal User's Guide at http://www.haskell.org/cabal/users-guide/index.html

Installation from Hackage

hs-webdriver is hosted on Hackage under the name webdriver. Thus, the simplest way to download and install the most recent version of hs-webdriver is to run:

cabal install webdriver

There are also options to do system-wide installation, version selection, and other build options; see cabal-install documentation.

Installation from this repository

To build and install a git revision for a single user on your system, run these commands from within the repository directory

Using cabal-install

cabal install

Using Cabal

For systems without cabal-install available, you can also run the Setup.hs script, as such:

runhaskell Setup.hs configure --user
runhaskell Setup.hs build
runhaskell Setup.hs install

For more build options, please refer to the Cabal documentation.

Getting Started

WebDriver is a client-server protocol. Since hs-webdriver only implements a WebDriver client, you must have a WebDriver server to which you can connect in order to make use of this library.

Using the Selenium Server

While you can use any WebDriver server out there, probably the simplest server to use with hs-webdriver is Selenium Server. You'll need an installation of the Java runtime to use this server. Once you've downloaded Selenium Server to your current working directory, you can start the server with this shell command:

java -jar selenium-server-standalone-*.jar

The server should now be listening at localhost on port 4444.

Hello, World!

With the Selenium server running locally, you're ready to write browser automation scripts in Haskell. Let's start with a simple example.

    {-# LANGUAGE OverloadedStrings #-}
    import Test.WebDriver

    myConfig :: WDConfig
    myConfig = defaultConfig

    main :: IO ()
    main = runSession myConfig $ do
      openPage "http://google.com"
      searchInput <- findElem (ByCSS "input[type='text']")
      sendKeys "Hello, World!" searchInput

hs-webdriver uses a very simple EDSL implemented within a state monad. Interacting with the remote browser is done via a sequence of commands within this monad. The state monad maintains implicit information about the WebDriver session between commands, so that individual commands only need to specify parameters relevant to the action they perform. If you're new to monads, there are plenty of resources available for learning on the web, but for now you can think of the WD monad as implementing a very simple imperative language operating on an implicit browser session.

Let's take a closer look at each piece of this example.

Demonic invocations: a bit of boilerplate

    {-# LANGUAGE OverloadedStrings #-}

hs-webdriver uses the Text type to represent Unicode character sequences, which is significantly more efficient than the standard Haskell structure for strings. This directive tells GHC to overload string literals so that they can be used to represent Text values (or, more generally, any other instance of IsString).

    import Test.WebDriver

This line is fairly straightforward; we need to import the library so that we can use it! Most of the basic API is available through the Test.WebDriver module, so this is the only import you should need for most tests. There are other modules that may be of interest for advanced usage; in particular, Test.WebDriver.Commands.Wait provides so-called "implicit waits" as defined by other WebDriver libraries. There are also modules that support custom Firefox and Chrome extensions, but these features are not fully stable.

Configuring a WebDriver session

    myConfig :: WDConfig
    myConfig = defaultConfig

To configure a new WebDriver session, we use the WDConfig type; this is a record type with various configuration fields. To connect to the Selenium server that we spawned earlier, the defaultConfig is sufficient. By default, the browser is set to Firefox, but that can be changed; the following configuration will use Google Chrome instead of Firefox for our test:

    myConfig :: WDConfig
    myConfig = defaultConfig { wdCapabilities = defaultCaps { browser = chrome } }

Note: To use Google Chrome, you need to install Google's proprietary ChromeDriver in a directory where it can be recognized by Selenium Server (see: https://code.google.com/p/selenium/wiki/ChromeDriver).

Initializing tests

    main :: IO ()
    main = runSession myConfig $ do

main is the standard entry point for a Haskell program, defined as a value of type IO a. In order to transform our WD action into an IO action, we use the runSession function, which has the type:

    runSession :: WDConfig -> WD a -> IO a

So we pass to runSession our configuration record along with a WebDriver "script" to perform, and it transforms the script into a side-effectful IO action. The WDConfig record is used to automatically initialize our session with the remote server.

Note: runSession does not automatically close the session it creates. This is intentional, as you may want to manually inspect the browser state after your code executes. If you want to have the session automatically close, you can use the finallyClose function to provide this behavior.

    main = runSession myConfig . finallyClose $ do

Actually writing tests!

      openPage "http://google.com"
      searchInput <- findElem (ByCSS "input[type='text']")
      sendKeys "Hello, World!" searchInput

Interaction with the browser is accomplished via WebDriver "commands", which are just function calls within the WD monad. Most of these commands are defined in the Test.WebDriver.Commands modules, and are fairly self-explanatory. In this example, openPage opens a new URL, and findElem searches for a DOM element on the current page which matches the given selector (possible selectors include ById, ByName, ByClass, ByTag, ByLinkText, ByCSS, and ByXPath). The DOM Element found by the result of the search is bound to the local variable searchInput, and sendKeys sends a sequence of emulated keystrokes to the given element.

This example contains all of the basic elements of a simple WebDriver test. For complete documentation on each command, check out the documentation for Test.WebDriver.Commands

Integration with Haskell Testing Frameworks

This package does not provide utilities to integrate with popular Haskell testing frameworks. However, other packages exist for this purpose:

Documentation

Documentation for hs-webdriver is available on Hackage at http://hackage.haskell.org/package/webdriver. You can also generate local HTML documentation from this source revision with the following shell command:

runhaskell Setup.hs haddock

Haddock will generate documentation and save it in dist/doc/html/webdriver

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