Gemini quick start

Gemini is the utility for regression testing of web pages appearance.

Its key features are:

• Compatibility with different browsers:

  • Google Chrome (tested in latest version)
  • Mozilla Firefox (tested in latest version)
  • IE8+
  • Opera 12+;

• Ability to test separate sections of a web page;

• Position and size of an element are calculated including its box-shadow and outline properties;

• Some special case differences between images (rendering artifacts, text caret, etc.) are ignored;

• CSS test coverage statistics.

Gemini is created at Yandex and will be especially useful to UI libraries developers.

Current document is a quick step-by-step guide that describes installation, configuration and usage of Gemini.

Dependencies

Required software:

1. WebDriver server implementation. There are few possible options:

   • Selenium Server – for testing in different browsers.

   • ChromeDriver - for testing in Google Chrome.

   • PhantomJS — launch with phantomjs --webdriver=4444 command.

   • Cloud WebDriver services, such as such as [SauceLabs] (http://saucelabs.com/) or BrowserStack

2. Compiler with support of C++11 ([email protected] or higher). This is a png-img requirement.

Installation

Global installation

To install the utility use npm command install:

npm install -g gemini

Global installation is used for commands launch.

Local installation

To write the tests you will also need local installation of Gemini. Run the following command in project directory:

npm install gemini

Configuration

Gemini is configured using .gemini.yml file at the root of the project. Lets say we want to run our tests only in locally installed PhantomJS.

In this case, the minimal configuration file will need to have only the root url of your web app and WebDriver capabilities of PhantomJS: For example,

rootUrl: http://yandex.com
browsers:
  PhantomJS:
    desiredCapabilities:
      browserName: phantomjs

Also, you need to run PhantomJS manually in a WebDriver mode:

phantomjs --webdriver=4444

In case you are using remote WebDriver server, you can specify its URL with gridUrl option:

rootUrl: http://yandex.com
gridUrl: http://selenium.example.com:4444/wd/hub

browsers:
  chrome:
    desiredCapabilities:
      browserName: chrome
      version: "45.0"

  firefox:
    desiredCapabilities:
      browserName: firefox
      version: "39.0"

You can also set up each browser to have its own node:

rootUrl: http://yandex.com

browsers:
  gridUrl: http://chrome-node.example.com:4444/wd/hub
  chrome:
    desiredCapabilities:
      browserName: chrome
      version: "45.0"

  firefox:
    gridUrl: http://firefox-node.example.com:4444/wd/hub
    desiredCapabilities:
      browserName: firefox
      version: "39.0"

Other configuration options

See the details of a config file structure and available options.

Writing tests

Each of the blocks that are being tested may be in one of the determined states. States are tested with the help of chains of step-by-step actions declared in test suites of a block.

For example, let's write a test for a search block at yandex.com:

var gemini = require('gemini');

gemini.suite('yandex-search', function(suite) {
    suite.setUrl('/')
        .setCaptureElements('.main-table')
        .capture('plain')
        .capture('with text', function(actions, find) {
            actions.sendKeys(find('.input__control'), 'hello gemini');
        });
});

We create a new test suite yandex-search and assume that we will capture the .main-table element from a root URL http://yandex.com. We know that the block has two states:

• plain – right after the page is loaded;
• with text – with hello gemini text inserted into .input__control.

States are executed one after another in order of definition without browser reload in between.

See the details of tests creation methods.

Using CLI

To complete the test creation procedure you need to take reference shots using the following command:

gemini gather [paths to test suites]

For test launch (to compare current state of a block with a reference shot) use the command:

gemini test [paths to test suites]

To see the difference between current state of a block and a reference picture more clearly, use HTML reporter:

gemini test --reporter html [paths to test suites]

You can use both console and HTML reporters at the same time:

gemini test --reporter html --reporter flat [paths to test suites]

See the details of interaction with CLI and available options.

GUI

Instead of a command line you can use graphical user interface of Gemini. It is located in gemini-gui package and must be installed additionally:

npm install -g gemini-gui

GUI advantages:

• Handy reference shots preview;

• Clear real-time demonstration of differences between a reference shot and current state of a block;

• Easy update of reference shots.

Plugins

Gemini can be extended with plugins. You could choose from the existing plugins or write your own. To use the plugin, install and enable it in your .gemini.yml:

system:
  plugins:
    some-awesome-plugin:
      plugin-option: value

Programmatic API

To use Gemini in your scripts or build tools you can use experimental programmatic API.