Difference between Functional Testing and Unit Testing

Functional Testing is carried out to ensure that the application’s overall functionality meets the business requirements. Unit Testing is performed on every individual element of an application to ensure that the element works as expected.

In the following sections, we will understand the differences, test case examples, and best practices to compare Functional Test vs Unit Test to understand the two better.

Functional Testing

Functional Testing tests the basic functionality of the application. It checks if the application runs as per the business requirements. You need to read and understand the operational requirements of an app before you begin writing the Functional test cases and testing the application.

It checks if the page transitions are smooth if the UI is flawless, if the application saves data when the user goes to the next screen and if the end-to-end functioning of the application is perfect. Functional Testing is only concerned about the ‘user perspective’. It checks for accessibility, usability, and good application experience. It is not concerned about the coding aspects of an application.

Types of Functional Testing:

• Unit Testing
• Sanity Testing
• Smoke Testing
• Utility Testing
• Integration Testing
• Regression Testing

How to create a functional test case?

1. As a QA, for a functional test to happen, the first step is to go through the business requirement document and familiarize themselves with the application. 
2. Form a test plan for the functionality to be tested. 
3. Select the right tool for the required type of functional Testing.
4. Compare the actual results to the expected results. It reveals if the test has passed or failed.

Functional Test Case Examples

To compare the difference between unit testing and functional testing, let’s check the order history of an e-commerce application.

Test Case 1: Log in to the application

Step 1: Use ‘Username’ and ‘Password’ to login. 

Step 2: On successful login, the user should see the dashboard.

Step 3: The dashboard should display Products in the web page’s body. The ‘My Account’ button should be in the top right corner. Next to ‘My Account’, there should be a’ Logout’ button.

Test Case 2: Navigating to the ‘Order History Page’

Step 1: On clicking ‘My Account’, the user should see ‘Order History, ‘Shipping address’, and ‘Wish list’.

Step 2: On clicking ‘Order History’, the user should see the list of past orders and the order number and tracking details.

Test Case 3: Display of Order History

Step 1: On clicking the specific order, the user should see the order date, product details, amount paid and shipping address of the specific order.

Step 2: The user should be able to go back to the previous order history page

Step 3: The user should be able to see canceled orders too.

Test Case 4: Navigating out of Order History Page

Step 1: User should be able to go to ‘Home’ page by clicking the ‘Home’ button on the top of the page. 

Step 2: The user should be able to log out by clicking on the ‘Logout’ button on the top right corner of the screen. 

The above example of testing the ‘Order History’ functionality is a test case example. Similarly, the entire application’s functionality is tested in Functional Testing.

Functional Testing can be manual or automated. A few popular Automation testing tools are Selenium and Cucumber.

Best Practices for Functional Testing

• It is prudent to document the test cases for easy tracking.
• Automate the Testing for faster and more effective results.
• Test cases should be reusable to save time.
• Always start with testing complex and high-risk functionalities first.

Get Started with Functional Testing

Unit Testing

Unit Testing is testing individual elements of an application. Each element, like a text box, button, and text display, is tested to check if it performs the expected actions. These individual elements are called ‘Units’ which gave rise to the term Unit Testing. It is run on even the smallest element in an app.

These elements are individually and independently tested for issues. It cannot be conducted on components that connect to an external entity. For example, Unit Tests cannot be undertaken on elements that connect to an external database, network, or file. These tests are conducted right from the beginning of the development phase.

How to create a Unit Test Case

1. Unit test cases evaluate every element of the application.
2. You must write a Test Case for every button click and text box input.
3. For every page of an application, multiple Unit Test cases are written to check the functionalities of all the page elements.
4. Unit test cases ensure that none of the elements is missed.
5. Multiple unit testing frameworks are available, and it’s essential to choose a proper one per the developer’s programming language.

Unit Test Case Examples

Let us use the same example for Functional Testing to compare the difference between Unit tests vs functional tests. Below is the sample test case for logging in to the e-commerce application.

Since it is a Unit Test case, we can take the individual elements like the ‘Username’ and ‘Password’ text boxes and the ‘Submit’ button.

Test Case 1: Username Input Text box

Step 1: The user should be able to click on the ‘Username’ text box and see the cursor inside

Step 2: ‘Username’ text box should accept alphabets. 

Step 3: ‘Username’ text box should accept numbers.

Step 4: ‘Username’ text box should have at least one alphabet

Step 5: ‘Username’ text box should have at least one number

Step 6: ‘Username’ text box should not accept special characters.

Step 7: ‘Username’ text length should not exceed 15 alphanumeric characters.

Test Case 2: Password Input Text box

Step 1: The user should be able to click on the ‘Password text box and see the cursor inside

Step 2: ‘Password’ text box should accept alphabets. 

Step 3: ‘Password’ text box should accept numbers.

Step 4: ‘Password’ text box should have at least one alphabet

Step 5: ‘Password’ text box should have at least one number

Step 6: ‘Password’ text box should have at least one special character.

Step 7: ‘Password’ text length should be eight and above.

Test Case 3: Submit button

Step 1: The user should be able to click on the ‘Submit’ button, 

Step 2: ‘Username’ text box should not be empty.

Step 3: ‘Password’ text box should not be empty.

Step 4: Validate the Username with the existing database.

Step 5: Validate Password with the existing database.

Step 6: If the Username and Password validation are successful, the user should be taken to the ‘Home’ page.

Step 7: If the Username and Password validation are unsuccessful, the error message ‘Invalid Credentials’ should be displayed.

Tools Used for Unit Testing

Automated tools like Selenium are popular tools that allow you to write test scripts in various programming languages like Java, Ruby, Python, C#, PHP, NodeJS, and Perl, among others. 

It is essential to choose a framework that is compatible with the programming language used by the developer.

• Popular Java Frameworks that can easily integrate with Selenium are JUnit and TestNG.
• We have a few frameworks for Python, among which PyUnit or UnitTest and PyTest are widely used.
• Test:Unit is a commonly used framework for Ruby Applications. 
• Javascript frameworks that integrate well with Selenium are JEST and Jasmine.

Best Practices for Unit Testing

• Unit Testing has to be done right from the beginning of development.
• It has to go hand-in-hand with development.
• It is always better to detect bugs early in development, and Unit Testing plays a significant role in doing so effectively.
• While writing the Unit Test Scripts, it is better to avoid logical conditions. It increases the risk of bugs. In case it is unavoidable, split it into separate tests. 
• Avoid interdependencies and treat every element to be independent functionalities.
• Following proper naming conventions while writing Unit Test cases for reusability and maintenance is essential.

Functional Testing vs Unit Testing: Differences

Let’s get into a detailed comparison for the Functional Test vs Unit Test below:

Closing Notes

For effective app testing, unit testing is done parallel to development to ensure the critical bugs are fixed immediately. It reduces the bugs to a great extent when the application is undergoing functional testing. The difference between Functional Testing and Unit Testing has been laid out in detail for you to choose from. Ensure to test on the BrowserStack infrastructure for accurate, reliable results. 

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