How to Use JUnit ErrorCollector [With Examples]

Different methods of ErrorCollector class

The ErrorCollector class in JUnit provides several methods to collect and report errors. Some of the most commonly used methods are:

• checkThat()
• addError(Throwable error)
• checkSucceeds(Executable executable)

checkThat()

The checkThat() method within JUnit’s ErrorCollector class lets you assert a test, gather any occurring errors, and continue with the test execution.

public <T> void checkThat(T value, Matcher<T> matcher)

The checkThat() method has two parameters: a String message and a Matcher object. The Matcher object is utilized to confirm if the actual value aligns with the expected value.

addError(Throwable error)

The addError() method includes an error in the ErrorCollector. This error can be any throwable object, including exceptions or assertion errors.

public void addError(Throwable error)

This method allows you to add a Throwable error as an input parameter. Although the test execution continues, it will ultimately be marked as failed.

checkSucceeds(Executable executable)

You can use the checkSucceeds() method in JUnit ErrorCollector to run a code block and ensure it doesn’t throw any exceptions. If an exception does occur, the error is collected, but the test keeps running.

public <T> T checkSucceeds(Callable<T> callable)

Demonstration: Using JUnit ErrorCollector with Selenium

Let’s examine a practical test case that includes assertions for verifying the Page Title and performing a product search in the search field. Despite any inconsistency in the Page Title assertion, the test should still successfully proceed with the product search using ErrorCollector.

Test Scenario

• Launch the TestMu AI Playground web page.
• Locate the Page Title and assert the Page Title.
• Search Product “IPod” in the search field.
• Locate the Page Title of the IPod product and assert the Page Title of the product.

Project Setup

To write test scripts, you can use any IDE like IntelliJ or Eclipse. However, for this demonstration, we will use the Eclipse IDE. Before we delve into writing the test scenarios, let’s take a moment to understand the directory structure of the Eclipse IDE.

Directory Structure

To begin, create a package named com.lambdatest.automation under src/test/java. Within this package, you’ll find three classes: ClassWithoutErrorCollector, ErrorCollectorItemsPageTest, and ErrorCollectorTest.

To illustrate, we have used Selenium 4.8 and JUnit 5.9.2 within the automation testing framework.

TestMu AI Setup

Before running the tests, there are a few steps you need to take care of.

Step 1: Create a TestMu AI account.

Step 2: Click on Account Settings from the list of options under your profile avatar.

Step 3: Copy the Username and Access key from the Password and Security tab.

Step 4: Now, you need to generate capabilities from the TestMu AI Capabilities Generator, which is more like a configuration that allows you to set the browser of your choice, its version, and operating system.

Step 4: Copy the generated capabilities and paste them into your code.

Implementation (without ErrorCollector)

Let’s now implement the code and run the test on the TestMu AI platform without using ErrorCollector. For that, you need first add some libraries into your pom.xml file.

FileName – pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>SeleniumFramework</groupId>
    <artifactId>SeleniumFramework</artifactId>
    <version>0.0.1-SNAPSHOT</version>


    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.seleniumhq.selenium/selenium-java -->
        <dependency>
            <groupId>org.seleniumhq.selenium</groupId>
            <artifactId>selenium-java</artifactId>
            <version>4.8.1</version>
        </dependency>


        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter-api</artifactId>
            <version>5.9.2</version>
            <scope>test</scope>
        </dependency>


        <dependency>
            <groupId>org.hamcrest</groupId>
            <artifactId>hamcrest-all</artifactId>
            <version>1.3</version>
            <scope>test</scope>
        </dependency>


    </dependencies>
</project>

Code to click on the Search box field.

driver.findElement(By.cssSelector("div[id='entry_217822'] input[placeholder='Search For Products']")).click();

To locate an element on the website, you can perform an inspection. To do this, visit the website, right-click anywhere, and choose the “Inspect” option. Then, find the element you’re interested in and identify it uniquely using Selenium locators by ID or its CSS Selector property. In this case, we will use the CSS Selector to locate the web element and the click() method to interact with it.

Now that you have the element, all you need to do is add your LT Username and Access Key, which can be found under the capabilities generator.

Simply insert the data generated from the TestMu AI platform into your code snippet, and you’re all set to run your test.

FileName – ClassWithoutErrorCollector.java

package com.lambdatest.automation;


import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;


import org.junit.After;
import org.junit.Before;
import org.junit.jupiter.api.Test;
import org.openqa.selenium.By;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.chrome.ChromeOptions;
import org.openqa.selenium.remote.DesiredCapabilities;
import org.openqa.selenium.remote.RemoteWebDriver;
import static org.junit.Assert.*;


public class ClassWithoutErrorCollector {


    public String username = "LT_USERNAME";
    public String accesskey = "LT_ACCESS_KEY";


    public static RemoteWebDriver driver = null;
    public String gridURL = "@hub.lambdatest.com/wd/hub";
    boolean status = false;


    @Before
    public void setUp() throws Exception {
       
        ChromeOptions browserOptions = new ChromeOptions();
        browserOptions.setPlatformName("Windows 10");
        browserOptions.setBrowserVersion("113.0");
        HashMap<String, Object> ltOptions = new HashMap<String, Object>();
        ltOptions.put("username", "username");
        ltOptions.put("accessKey", "accesskey ");
        ltOptions.put("project", "Error Collector");
        ltOptions.put("w3c", true);
        ltOptions.put("plugin", "java-junit");
        browserOptions.setCapability("LT:Options", ltOptions);
        try {
            driver = new RemoteWebDriver(new URL("https://" + username + ":" + accesskey + gridURL), browserOptions);
        } catch (MalformedURLException e) {
            System.out.println("Invalid grid URL");
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }


    @Test
    public void testSimple() throws Exception {


        // navigating to the application under test
        driver.get("https://ecommerce-playground.lambdatest.io/");


        // maximize window
        driver.manage().window().maximize();


        Thread.sleep(1000);


        // validating the Page Title
        String ActualString = "Your Stores";
        String ExpectedString = driver.getTitle();
        System.out.println(ExpectedString);


        assertEquals(ExpectedString, ActualString);


        Thread.sleep(1000);


        driver.findElement(By.cssSelector("div[id='entry_217822'] input[placeholder='Search For Products']")).click();
        Thread.sleep(1000);
        driver.findElement(By.cssSelector("div[id='entry_217822'] input[placeholder='Search For Products']"))
                .sendKeys("IPod");
        Thread.sleep(3000);
        driver.findElement(By.xpath("//button[normalize-space()='Search']")).click();
        Thread.sleep(1000);
        String ActualProductPageTitle = "Search - iPod";
        String ExpectedProductPageTitle = driver.getTitle();
        System.out.println(ExpectedProductPageTitle);
        Thread.sleep(3000);


    }


    @After
    public void tearDown() throws Exception {
        if (driver != null) {
            ((JavascriptExecutor) driver).executeScript("lambda-status=" + status);
            driver.quit();
        }
    }


}

Result:

As you can see, the test execution came to a halt at the first assert statement. To tackle this problem, we can utilize ErrorCollector.

Implementation (with ErrorCollector)

The following two classes, ErrorCollectorTest and ErrorCollectorItemsPageTest, use JUnit ErrorCollector to ensure that the test execution continues without interruption.

FileName – ErrorCollectorTest.java

package com.lambdatest.automation;


import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;


import org.hamcrest.Matcher;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ErrorCollector;
import org.openqa.selenium.By;
import org.openqa.selenium.chrome.ChromeOptions;
import org.openqa.selenium.remote.DesiredCapabilities;
import org.openqa.selenium.remote.RemoteWebDriver;




public class ErrorCollectorTest {


    public String username = "LT_USERNAME";
    public String accesskey = "LT_ACCESS_KEY";
    public static RemoteWebDriver driver = null;
    public String gridURL = "@hub.lambdatest.com/wd/hub";
    boolean status = false;


    @Before
    public void setUp() throws Exception {
       
        ChromeOptions browserOptions = new ChromeOptions();
        browserOptions.setPlatformName("Windows 10");
        browserOptions.setBrowserVersion("113.0");
        HashMap<String, Object> ltOptions = new HashMap<String, Object>();
        ltOptions.put("username", username);
        ltOptions.put("accessKey", accesskey);
        ltOptions.put("project", "Error Collector");
        ltOptions.put("w3c", true);
        ltOptions.put("plugin", "java-junit");
        browserOptions.setCapability("LT:Options", ltOptions);
       
        try {
            driver = new RemoteWebDriver(new URL("https://" + username + ":" + accesskey + gridURL), browserOptions);
        } catch (MalformedURLException e) {
            System.out.println("Invalid grid URL");
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }
   
   
     @Rule
        public final ErrorCollector collector = new ErrorCollector();


      @Test
        public void testWithErrorCollector() throws InterruptedException {
          System.out.println("FirstParallelUnitTest first() start => " + Thread.currentThread().getName());
        // navigating to the application under test
            driver.get("https://ecommerce-playground.lambdatest.io/");


            // maximize window
            driver.manage().window().maximize();


        Thread.sleep(1000);


            // validating the Page Title
            String ActualString = "Your Stores";
            String ExpectedString = driver.getTitle();
           
         
              System.out.println("value coming in : " + ExpectedString);
              System.out.println("value to check  : " + ActualString);
              collector.checkThat("Check values match", ActualString, equalTo(ExpectedString));
               
                 collector.checkThat(ExpectedString, equalTo(ActualString));
                 
                 collector.checkThat(ExpectedString, "Not matched",equalTo(ActualString));
                 
           
            driver.findElement(By.cssSelector("div[id='entry_217822'] input[placeholder='Search For Products']")).click();
            Thread.sleep(1000);
            driver.findElement(By.cssSelector("div[id='entry_217822'] input[placeholder='Search For Products']"))
                    .sendKeys("IPod");
            Thread.sleep(3000);
            driver.findElement(By.xpath("//button[normalize-space()='Search']")).click();
            Thread.sleep(1000);
            String ActualProductPageTitle = "Search - iPod";
            String ExpectedProductPageTitle = driver.getTitle();
            System.out.println(ExpectedProductPageTitle);
            Thread.sleep(3000);
            System.out.println("Test Completed");
        }
     
     
     


    private Matcher equalTo(String actualString) {
        // TODO Auto-generated method stub
        return null;
    }
}

FileName – ErrorCollectorItemsPageTest.java

package com.lambdatest.automation;


import java.net.MalformedURLException;
import java.net.URL;
import java.util.HashMap;


import org.hamcrest.Matcher;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ErrorCollector;
import org.openqa.selenium.By;
import org.openqa.selenium.chrome.ChromeOptions;
import org.openqa.selenium.remote.DesiredCapabilities;
import org.openqa.selenium.remote.RemoteWebDriver;


public class ErrorCollectorItemsPageTest {


    public String username = "LT_USERNAME";
    public String accesskey = "LT_ACCESS_KEY";


    public static RemoteWebDriver driver = null;
    public String gridURL = "@hub.lambdatest.com/wd/hub";
    boolean status = false;


    @Before
    public void setUp() throws Exception {


        ChromeOptions browserOptions = new ChromeOptions();
        browserOptions.setPlatformName("Windows 10");
        browserOptions.setBrowserVersion("113.0");
        HashMap<String, Object> ltOptions = new HashMap<String, Object>();
        ltOptions.put("username", username);
        ltOptions.put("accessKey", accesskey);
        ltOptions.put("project", "Error Collector");
        ltOptions.put("w3c", true);
        ltOptions.put("plugin", "java-junit");
        browserOptions.setCapability("LT:Options", ltOptions);


        try {
            driver = new RemoteWebDriver(new URL("https://" + username + ":" + accesskey + gridURL), browserOptions);
        } catch (MalformedURLException e) {
            System.out.println("Invalid grid URL");
        } catch (Exception e) {
            System.out.println(e.getMessage());
        }
    }


    @Rule
    public final ErrorCollector collector = new ErrorCollector();


    @Test
    public void testWithErrorCollector() throws InterruptedException {


        System.out.println("SecondParallelUnitTest first() start => " + Thread.currentThread().getName());
        // navigating to the application under test
        driver.get("https://ecommerce-playground.lambdatest.io/");


        // maximize window
        driver.manage().window().maximize();


        Thread.sleep(1000);


        // clicking on MyAccount dropdown
        driver.findElement(
                By.xpath("//ul[@class='navbar-nav horizontal']//span[@class='title'][normalize-space()='Blog']"))
                .click();


        // validating the Page Title
        String ActualString = "Blog-Poco Theme";
        String ExpectedString = driver.getTitle();


        System.out.println("value coming in : " + ExpectedString);
        System.out.println("value to check  : " + ActualString);


        collector.checkThat("Check values match", ActualString, equalTo(ExpectedString));


        collector.checkThat(ExpectedString, equalTo(ActualString));


        collector.checkThat(ExpectedString, "Not matched", equalTo(ActualString));


        Thread.sleep(3000);


        /// navigate to account login page
        driver.findElement(By.xpath("//a[@role='button']//span[@class='title'][normalize-space()='My account']"))
                .click();
        Thread.sleep(3000);
        System.out.println(driver.getTitle());


        System.out.println("Test Completed");
    }


    private Matcher equalTo(String actualString) {
        // TODO Auto-generated method stub
        return null;
    }
}

Code Walkthrough

Step 1: Import the packages of JUnit and other methods.

Step 2: Create the RemoteWebDriver reference. RemoteWebDriver is a class that implements the WebDriver interface to execute the tests on the RemoteWebDriver server on a remote machine. It is implemented under the package below.

Step 3: The method implemented in @BeforeTest annotation sets the browser’s capabilities. A RemoteWebDriver instance is created with the desired browser capabilities, with the Selenium Grid URL set to the cloud-based Selenium Grid on TestMu AI [@hub.lambdatest.com/wd/hub].

Step 4: All the test navigation steps are implemented under the @Test annotation. Here is how we navigate to the desired URL.

Step 5: Checking the actual Title of the page and the expected Title of the page.

Step 6: Inspect the ‘Search Box’ text field using any locator. We have used CSS Selector as a locator and entered the “IPod” text in the search field using the sendKeys() method in Selenium.

Step 7: Thread.sleep() in Selenium pauses the current thread for a specified time, often 3000 milliseconds, to wait for a page or application to load before continuing with the next code line.

However, it is preferred to use Selenium’s implicit and explicit waits over Thread.sleep(), allowing more efficient and responsive synchronization with the web page, reducing unnecessary wait times. For a deeper understanding of implicit and explicit wait commands in Selenium, refer to this article on Selenium Waits.

Step 8: To utilize JUnit rules, we apply the @Rule annotation to methods or fields. Keep in mind that the annotated methods must be public and non-static.

This concept involves rules or methods that provide outcomes. In this case, we’re implementing the @Rule annotation, which gathers and reports all errors together in one go.

Step 9: Collecting all the errors and asserting.

TestMu AI Dashboard

The tests were successfully executed on TestMu AI’s Selenium Grid, and the TestMu AI Web Automation Dashboard indicates the status of the test execution.