What is this Error: at com.google.common.base.Preconditions.checkNotNull

Question

I am a new automation tester, Working on sample test scripts, Need some help from you guys, I have tried to use POM and basic TestNG.

I have created 2 packages - pages and testcases.

I am getting some error when I am trying to access the "ClickJoin, Enterusername" methods from my pages packages. I had tried figuring out the issue, but was unable to get to why this error is occurring.

Below is the Error: java.lang.NullPointerException at com.google.common.base.Preconditions.checkNotNull

My Code from the "pages" package: package com.gptoday.pages;

import org.openqa.selenium.By;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.support.ui.ExpectedConditions;
import org.openqa.selenium.support.ui.WebDriverWait;

public class Login {

public WebDriver driver;
public WebDriverWait wait;
By join = By.xpath("//*[@id='members']/a[1]");
By username = By.id("username");
By password = By.id("password");
By loginButton = By.xpath("//*[@id='normallogin']/div[4]/p/input[2]");

public Login (WebDriver driver){
    this.driver=driver;
}
    public void ClickJoin(){
        wait = new WebDriverWait(driver,10);
        //driver.findElement(join).click();

wait.until(ExpectedConditions.visibilityOfElementLocated(join)).click();
    }

    public void EnterUsername(){
        wait = new WebDriverWait(driver, 10);


wait.until(ExpectedConditions.visibilityOfElementLocated(username)).click();
        wait.until(ExpectedConditions.visibilityOfElementLocated(username)).sendKeys("Test username");
        System.out.println("Username Entered");
    }

    public void EnterPassword(){
        driver.findElement(password).clear();
        driver.findElement(password).click();
        System.out.println("Password Entered");
    }

        public void ClickButton(){
            wait = new WebDriverWait(driver, 10);
            //driver.findElement(loginButton).click();
 wait.until(ExpectedConditions.visibilityOfElementLocated(loginButton)).click();
            System.out.println("Login Button Clicked");
        }
    }

My Code from the "TestCases" package: This code is of my base class.

package com.gptoday.com.gptoday.testcases;

import org.testng.annotations.Test;
import org.testng.annotations.BeforeMethod;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.firefox.FirefoxProfile;
import org.openqa.selenium.firefox.internal.ProfilesIni;
import org.testng.annotations.AfterMethod;
import org.openqa.selenium.firefox.internal.ProfilesIni;

public class Base {
    public WebDriver driver;

    @BeforeMethod
    public void BaseSetup(){
        ProfilesIni prof = new ProfilesIni();
        FirefoxProfile ffProfile= prof.getProfile ("vishvesh");
        ffProfile.setAcceptUntrustedCertificates(true);
        ffProfile.setAssumeUntrustedCertificateIssuer(false);

        String BaseUrl = "https://www.gptoday.com";
        System.setProperty("webdriver.gecko.driver", "G:/Workplace/AutomationSetupFiles/Geckdriver/geckodriver.exe"); 
        driver = new FirefoxDriver (ffProfile);
        driver.get(BaseUrl);
        driver.manage().window().maximize();
    }

    @AfterMethod
    public void afterTest() {
        System.out.println("Success");
      }
}

**Below the the code for the test case.**
package com.gptoday.com.gptoday.testcases;

import org.testng.annotations.Test;
import com.gptoday.pages.Login;
import org.openqa.selenium.WebDriver;


public class LoginVerification extends Base {

    public WebDriver driver;
    public Login obj = new Login(driver);

    @Test
    public void Verify()
    {
        obj.ClickJoin();
        obj.EnterUsername();
    }
}

**Error:**
Success
FAILED: Verify
java.lang.NullPointerException
    at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:770)
    at org.openqa.selenium.support.ui.FluentWait.<init>(FluentWait.java:96)
    at org.openqa.selenium.support.ui.WebDriverWait.<init>(WebDriverWait.java:71)
    at org.openqa.selenium.support.ui.WebDriverWait.<init>(WebDriverWait.java:45)
    at com.gptoday.pages.Login.ClickJoin(Login.java:22)
    at com.gptoday.com.gptoday.testcases.LoginVerification.Verify(LoginVerification.java:16)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:108)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:661)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:869)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1193)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:126)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
    at org.testng.TestRunner.privateRun(TestRunner.java:744)
    at org.testng.TestRunner.run(TestRunner.java:602)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:380)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:375)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:340)
    at org.testng.SuiteRunner.run(SuiteRunner.java:289)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1301)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1226)
    at org.testng.TestNG.runSuites(TestNG.java:1144)
    at org.testng.TestNG.run(TestNG.java:1115)
    at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:132)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:230)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:76)

Answer 1

Here's the reason behind the error you are getting:

In both Login & EnterUsername methods while you defined the wait you have passed the instance of Webdriver & interval. Now whenever Selenium detects this particular type of argument Selenium treats this as FluentWait. Now when you actually implement a FluentWait you have to import those two libraries "com.google.common.base.Function" which will address the error you are facing. Of course you have to import "FluentWait" as well.

Let me know if this helps you.

Answer 2

By modifying the code in the "Login.Java" class.. The issue was related to driver being null as I did not extend "Base" in the "Login" class.