Selenium Grid allows the execution of WebDriver scripts on remote machines (virtual or real) by routing commands sent by the client to remote browser instances. It aims to provide an easy way to run tests in parallel on multiple machines.
Selenium Grid allows us to run tests in parallel on multiple machines, and to manage different browser versions and browser configurations centrally (instead of in each individual test).
Purposes and main functionalities of Selenium GRID
- Central entry point for all tests
- Management and control of the nodes / environment where the browsers run
- Scaling
- Running tests in parallel
- Cross platform testing
- Load balancing
To run your tests against multiple browsers, multiple versions of browser, and browsers running on different operating systems.
To reduce the time it takes for the test suite to complete a test pass.
Selenium GRID Architecture
- Intermediary and manager
- Accepts requests to run tests
- Takes instructions from client and executes them remotely on the nodes
- Manages threads
A Hub is a central point where all your tests are sent. Each Selenium Grid consists of exactly one hub. The hub needs to be reachable from the respective clients (i.e. CI server, Developer machine etc.) The hub will connect one or more nodes that tests will be delegated to.
Nodes
- Where the browsers live
- Registers itself to the hub and communicates its capabilities
- Receives requests from the hub and executes them
Nodes are different Selenium instances that will execute tests on individual computer systems. There can be many nodes in a grid. The machines which are nodes do not need to be the same platform or have the same browser selection as that of the hub or the other nodes. A node on Windows might have the capability of offering Internet Explorer as a browser option, whereas this wouldn’t be possible on Linux or Mac.
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