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Front End Performance Testing


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Anticipating the Application Response

When you click a Submit button, you know that you have to wait a second or two for your action to reach the server, and for the server to respond, before you do anything else. If you're trying to test the response, and what happens afterwards, then you need to build that waiting time into your test. Otherwise, the test might fail because the elements that are expected for the next step haven't loaded into the browser you. The WebDriver API supports two basic techniques for anticipating browser response by waiting: implicit waits and explicit waits 

Do Not Mix Explicit and Implicit Waits

Do not mix implicit and explicit waits. Doing so can cause unpredictable wait times. For example setting an implicit wait of 10s and an explicit wait of 15 seconds, could cause a timeout to occur after 20 seconds. 

Wait Strategies

Implicit waits set a maximum time that the Appium server will continue trying to find an element. Using implicit waits is not a best practice because application response times are not definitely predictable and fixed elapsed times are not applicable to all interactions. Using explicit waits requires more technical sophistication, but is a Sauce Labs best practice.

This example code illustrates how you could use an implicit wait to anticipate web browser response after submitting the login form.

Implicit Wait Java Example
driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);

Explicit waits wait until an expected condition occurs on the web page, or until a maximum wait time elapses. To use an explicit wait, you create an instance of the WebDriverWait class with a maximum wait time, and you invoke its until method with an expected condition. 

The WebDriver API provides an ExpectedConditions class with methods for various standard types of expected condition. These methods return an instance of an expected condition class. You can pass an invocation of these standard expected-condition methods as argument values to until method. You can also pass - in ways that your programming language and its WebDriver API support - any function, code block, or closure that returns a boolean value or an object reference to a found web element as an argument value to the until method. How this is done varies over programming languages. The until method checks repeatedly, until the maximum wait time elapses, for a true boolean return value or a non-null object reference, as an indication that the expected condition has occurred.

This example code illustrates how you could use an explicit wait to anticipate web browser response after submitting the login form.

Explicit Wait Java Example
WebDriverWait wait = new WebDriverWait(driver, 10); WebElement messageElement = wait.until( ExpectedConditions.presenceOfElementLocated("loginResponse")) );
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