Need help on Desiredcapabilities class - selenium-grid

Question

Hi I am learning selenium grid for the first time.I am unable to understand why Desired capabilities class is used to set browser name and platform details in a remote machine.
please let me know if there is any proper documentation on it apart from google-wiki page
Thanks
prathima

Answer 1

Not all remote machines (or sessions) support the features requested by a user. E.g. user may want to use Chrome on Windows but some machines are only running Firefox on Linux.
The desiredCapabilities is used to describe the features of a session requested by user. You can refer to this link and this link for more info.

Answer 2

- when user send request to remote machine to run a particular test on
a particular browser on a particular platform.
- It doesn't mean that all the remote machine will support all the
features requested by user such as (Particular browser on a
particular machine).
**Example:**
- If user request to execute a testcase on internet explorer on Linux
platform. It doesn't mean that always Linux machine has internet
explorer it would have firefox not internet Explorer(Because it is
open source).
- Linux machine doesn't support the features requested by a User. so
that, that point of time we will use DesiredCapabilites class to set
the platform , Browser Name and version of browser of Remote Machine
to execute the Test.

Answer 3

Example:
package grid;
import static org.junit.Assert.*;
import java.net.URL;
import java.util.concurrent.TimeUnit;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.openqa.selenium.By;
import org.openqa.selenium.Platform;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.remote.DesiredCapabilities;
import org.openqa.selenium.remote.RemoteWebDriver;
public class SimpleGridTest
{
WebDriver driver;
String baseUrl , nodeUrl;
#Before
public void setUp() throws Exception
{
WebDriver driver;
String baseUrl , nodeUrl;
baseUrl = "https://www.facebook.com";
nodeUrl = "http://192.168.10.21:5568/wd/hub";
DesiredCapabilities capability = DesiredCapabilities.firefox();
capability.setBrowserName("firefox");
capability.setPlatform(Platform.WIN8_1);
driver = new RemoteWebDriver(new URL(nodeUrl),capability);
driver.manage().window().maximize();
driver.manage().timeouts().implicitlyWait(2, TimeUnit.MINUTES);
}
#Test
public void test() throws InterruptedException
{
driver.manage().window().maximize();
driver.get("https://www.google.co.in");
driver.findElement(By.linkText("Gmail")).click();
driver.findElement(By.id("Email")).sendKeys("abc#gmail.com");
driver.findElement(By.id("Passwd")).sendKeys("1234");
driver.findElement(By.id("signIn")).click();
}
#After
public void tearDown() throws Exception
{
driver.quit();
}
}