Selenium 页面对象模型框架

Question

I am learning page object model using selenium webdriver and can someone advise me on these?

1 - Why does each page in the POM have constructors to initialize the webdriver object? (like the one below) What will happen if webdriver is not initialized?

public class New_Register 
{
    WebDriver driver;

    public New_Register(WebDriver driver)
    {
        this.driver=driver;
    }

    @FindBy(xpath=".//input[@id='emailAdd']") WebElement EmailID;
}

2 - Is POM a framework or design pattern in Selenium Webdriver?

Answer 1

If your Page Object inherits from LoadableComponent class forcing you to override load and isloaded methods and you use the PageFactory.initElements to initialize proxies for your webelements(@Find...) I think you are using it as a framework. If you handle all this stuff taking care of checking whether your page is loaded, getting webelements, passing the pageobject etc but you using a class to model a page or part of its functionality it may be regarded as a design pattern.

If you do not pass in the driver you will have to initialize driver yourself. Else you will get the favorite Null Pointer Exception when you call any method on it. Also when you call PageFactory.initElements it first looks for a constructor on the pageobject with driver as the sole argument. Then only it looks for the default one if it does not get the previous one, then you will have to handle driver initialization yourself.

Answer 2

a) I will answer your 2nd question first - Page Object Model in UI Test Automation is a design pattern NOT a Framework. A Framework provides you easy access to generic methods/configs etc. on top of which you can build your application (let it be a Web App or Test Automation Suite) and reduces much of our boilerplate code. A good framework should make use of existing libraries and user-written code and should do most of the heavy lifting. For example, the TestNG library can be considered as a Testing Framework that provides us testing related features (like running tests, supplying data to our tests, defining rules for running the tests like priority etc.).

Whereas a design pattern provides a solution to commonly occurring or repeating design problems in your project.
For example, you may need to instantiate a single instance of Webdriver or any Database reading object to control its action throughout its execution. Now to solve this you may use a Singleton Pattern in your code. Reading about other design patterns like Facade and Builder will provide more clarity on this. Now similarly you have POM which is useful in reducing code duplication and improving test case maintenance since we segregate respective Page classes from their tests.

Again do not get confuse Design Pattern with Design Principles like DRY and SOLID etc.

So in a nutshell all answers different problems :)

b) for your first question kindly refer to my already existing answer provided below - And as @Grasshopper rightly mentioned, you will get a null pointer exception if you do not implement the constructors.

https://stackoverflow.com/a/70078344/6053575

Do let me know if you have any further questions.