Reasons for ScriptTimeoutException in Selenium

Pragya Yadav

Timeouts are the mechanisms Selenium uses to let the WebDriver know how much maximum time to allocate for a particular operation or condition. An exception is thrown when the operation is not completed within the specified time.

These timeouts help identify the situations where a script takes too long to execute, or some operation takes longer than expected, such as element loading.

A script timeout is used to set the time for an asynchronous script to finish execution. If the script does not finish execution within the specified time, then a ScriptTimeoutException is thrown. This timeout is specifically helpful while executing executeAsyncScript to run JavaScript.

Let us have a look at the reasons for ScriptTimeoutException:

Why does ScriptTimeoutException Happen?

Here are a few reasons for ScriptTimeoutException in Selenium:

Long-running scripts

There could be cases when the script takes longer than expected time to execute, such as when processing large amounts of data. Another example is when a script is waiting for some other conditions, and there is no proper exit strategy, and it keeps waiting. In such situations, the ScriptTimeoutException is thrown in Selenium.

WebDriver driver = new ChromeDriver();

driver.manage().timeouts().setScriptTimeout(2, TimeUnit.SECONDS);

try {
  // A script that is expected to take more than 2 seconds
  driver.executeAsyncScript("window.setTimeout(arguments[arguments.length - 1], 3000);");
} catch (ScriptTimeoutException e) {
  System.out.println("Script took too long to run and timed out");
}

In the above example, the script is set to complete in 2 seconds, while the script will take 3 seconds to execute as in executeAsyncScript. Therefore, a ScriptTimeoutException is thrown because the script cannot be completed in the stipulated time.

Asynchronous operations waiting

When scripts involve asynchronous operations such as AJAX calls, these operations take longer than expected. Another case is to keep the script waiting for completion, leading to an indefinite wait. Such scenarios cause ScriptTimeoutException in Selenium.

WebDriver driver = new ChromeDriver();

driver.manage().timeouts().setScriptTimeout(5, TimeUnit.SECONDS);

try {
  // Script with an AJAX call that might take an unknown amount of time
  String script = "var callback = arguments[arguments.length - 1];" +
        "fetch('https://some-api.com/data').then(function(response) {" +
          " callback(response.json());" +
        "}).catch(function(error) {" +
          " callback('Error');" +
        "});";
  driver.executeAsyncScript(script);
} catch (ScriptTimeoutException e) {
  System.out.println("Script timed out due to a long-running AJAX call");
}

Incorrect timeout

If you have set a shorter timeout for the script and the script usually takes longer than it, then the exception is bound to be thrown. Hence, properly evaluate the time required for the script to run and then set the timeout accordingly successfully.

Unresponsive web elements or browser

If the web elements or the browser are unresponsive, that may cause the script to hang. Since the script has stopped running, the execution gets halted, the timeout exceeds, and the exception occurs.

Network issues or delays

The script might fetch and wait for remote resources where the communication is through networks. If there happens to be any delay or issue in the network communication, the script will continue to wait indefinitely. In such cases, the timeout will be exceeded, and Selenium throws ScriptTimeoutException.

Ways to Resolve ScriptTimeoutException

The most important technique to avoid ScriptTimeoutException is to manage allocated script execution time effectively in the test scripts. Follow the below methods to prevent and resolve ScriptTimeoutException:

Increase script timeout value

WebDriver driver = new ChromeDriver();

// Setting the script timeout to 60 seconds
driver.manage().timeouts().setScriptTimeout(60, TimeUnit.SECONDS);

try {
  driver.executeAsyncScript("window.setTimeout(arguments[arguments.length - 1], 50000);");
} catch (ScriptTimeoutException e) {
  System.out.println("Script execution took too long");
}

Review and optimize the script

You can review and optimize the script to make it quicker and avoid falling into the ScriptTimeOutException. Some optimizations could be to reduce complexity, optimize loop processing, enhance data processing, etc.

Properly handle the asynchronous operations

String asyncScript = "var callback = arguments[arguments.length - 1];" +
        "fetch('https://api.example.com/data')" +
        ".then(response => response.json())" +
        ".then(data => callback(data))" +
        ".catch(error => callback('Error'));";
try {
  Object result = driver.executeAsyncScript(asyncScript);
} catch (ScriptTimeoutException e) {
  System.out.println("Asynchronous script timed out");
}

Use explicit waits

WebDriverWait wait = new WebDriverWait(driver, 20);
wait.until(ExpectedConditions.visibilityOfElementLocated(By.id("someId")));
// Now perform actions with the element

Split longer scripts into smaller ones

// Executing a long script in smaller parts
for (String part : scriptParts) {
  driver.executeAsyncScript(part);
}

Handle network issues and delays

String networkDependentScript = "var callback = arguments[arguments.length - 1];" +
        "fetch('https://api.example.com/data', { timeout: 10000 })" + // Setting a timeout for the fetch request
        ".then(response => response.json())" +
        ".then(data => callback(data))" +
        ".catch(error => callback('Error'));";
try {
  Object result = driver.executeAsyncScript(networkDependentScript);
} catch (ScriptTimeoutException e) {
  System.out.println("Network-dependent script timed out");
}

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