UnknownMethodException in Selenium: How to Handle?

Hari Mahesh

As we know, the exceptions in Selenium are used to handle any unexpected situation while executing the test scripts. So, these exceptions gracefully handle the errors. Otherwise, the test cases fail abruptly without any information on the error. In this article, we will be discussing UnknownMethodException. Read on to know what this exception is, how it occurs, and how to avoid it.

Reasons for UnknownMethodException

Here are the common reasons that may cause UnknownMethodException:

Typographical Error in Method Name

This is one of the most common reasons for an UnknownMethodException. It occurs when there’s a spelling mistake in the method name.

Example: If you try to call document.getElemntById("id") in JavaScript, you’ll get an error because the correct method is getElementById. This kind of error is often overlooked because it’s easy to misspell method names, especially in languages that don’t provide compile-time checking for this.

Method Does Not Exist in the Class/Object

This happens when you attempt to call a method that isn’t defined in the class or object you’re working with. This indicates a misunderstanding or lack of knowledge about the class’s available methods.

Example: If you have a Car class in Java that does not have a method getOwnerName(), and you try to call this method (car.getOwnerName()), you will encounter an UnknownMethodException.

Incorrect API Usage or Version Mismatch

Sometimes, a method might exist in one version of a library or API but not in another. You’ll get this exception if your codebase uses a version where the method doesn’t exist.

Example: A method introduced in version 2.0 of a library won’t be available if you’re using version 1.5. It’s important to keep track of the versions of the libraries or frameworks you are using and ensure compatibility with your code.

Scope and Visibility Issues

If you’re trying to access a method that’s not visible in your current scope, you’ll face an UnknownMethodException. This is related to object-oriented programming principles, where the access to methods is controlled by access modifiers like public, private, and protected.

Example: In Java, trying to call a private method from outside its class will lead to this error.

Missing Library or Dependency:

If your code depends on external libraries or frameworks that are not properly included or installed, any attempt to use their methods will result in an UnknownMethodException.

Example: If you’re trying to use a method from a third-party Python library without importing the library (import library_name) or without the library being installed, Python will throw an error indicating that it doesn’t recognize the method.

Resolving UnknownMethodException in Selenium

You can adopt the below steps to resolve UnknownMethodException in Selenium:

• Correct Typographical Errors in Method Names: If the exception is due to a typo in the method name, carefully check the spelling and case of the method. Programming languages are case-sensitive, so getdata() and getData() would be treated as different methods. Use your IDE’s auto-completion feature to avoid such errors.
  For example, if you’ve mistakenly written document.getElemntById() in JavaScript, correct it to document.getElementById().

  // Incorrect
  var element = document.getElemntById("example"); // Throws an error
  
  // Corrected
  var element = document.getElementById("example"); // Correct method

• Ensure the Method Exists in the Class/Object: Ensure that the method you’re trying to call actually exists in the class or object. Check the class definition or the documentation of the object you’re working with.
  If you’re working with a Car class in Java that doesn’t have a getOwnerName() method, either add this method to the class or use an existing method like getModel().

  // Java Example
  
  class Car {
    private String model;
  
    public String getModel() {
      return model;
    }
  }
  
  Car car = new Car();
  
  // Incorrect
  // String owner = car.getOwnerName(); // Throws an error
  // Corrected
  String model = car.getModel(); // Correct method

• API Usage or Version Mismatch: Make sure you’re using the correct version of the library or framework that contains the method you need. Review the documentation for version-specific information. If a method was introduced in a later version, you might need to update your library.
  For instance, if a method is available in jQuery 3.0 but you’re using 2.0, you should update to the correct version.

  # Python Example
  # Incorrect: Using a newer method not available in the current version
  # import library
  # library.new_method()
  # Corrected
  
  import library
  
  library.existing_method() # Use a method that exists in the current version

• Scope and Visibility Issues: If the issue is due to scope or visibility, modify your code with respect to object-oriented principles. If possible, you may need to change the method’s access modifier or use a different accessible method.
  For example, if you’re trying to access a private method from outside its class in Java, you either need to make the method public or use a public getter method to access the required property.

  // Java Example
  
  class Car {
    private String getSecretCode() {
      return "XYZ123";
    }
  
    public String getPublicCode() {
      return getSecretCode();
    }
  }
  
  Car car = new Car();
  
  // Incorrect
  // String secretCode = car.getSecretCode(); // Throws an error
  // Corrected
  String code = car.getPublicCode(); // Access via a public method

• Include Missing Libraries or Dependencies: Ensure that all external libraries or dependencies your code relies on are properly included and installed. In a Python project, for instance, if you’re trying to use a method from an external library, first install the library using a package manager like pip (pip install library_name) and then import it in your script (import library_name).

  # Python Example
  # Incorrect: Using a library method without importing
  # someLibrary.someMethod()
  # Corrected
  
  import someLibrary
  
  someLibrary.someMethod() # Correctly imported

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Though exceptions are useful, they also waste our time and effort since we need to find the root cause and then fix the code. It becomes tedious when the organization looks for frequent releases. What is expected from an automation tool is that it should be smart enough to identify the scenarios and create test scripts with minimal effort from the testing team. However, Selenium fails to fulfill the expectations, and there are many disadvantages of the Selenium framework. That is the reason why organizations are looking for better alternatives today.

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