Gray Box Testing - Software Testing

Last Updated : 22 Jul, 2025

Gray Box Testing is a software testing technique that combines elements of the Black Box Testing technique and the White Box Testing technique. Gray box testing is also known as translucent testing or API testing.

Objectives of Gray Box Testing:

To provide the combined advantages of both black box testing and white box testing.
To combine the input of developers as well as testers.
To improve overall product quality.
To reduce the overhead of the long process of functional and non-functional testing.
To provide enough free time to developers to fix defects.
To test from the user's point of view rather than a designer's point of view.

Explore the complete details of Gray Box Testing, including its techniques, advantages, and limitations, in our article. For a thorough understanding of various testing methodologies and tools, check out our course, ” Complete Guide to Software Testing,” available at GeeksforGeeks.

Gray Box Testing Techniques

Here are the main techniques of the Gray Box Testing which are included in the gray box testing:

1. Matrix Testing

In Matrix Testing technique, business and technical risks which are defined by the developers in software programs are examined. Developers define all the variables that exist in the program. Each of the variables has an inherent technical and business risk and can be used with varied frequencies during its life cycle.

2. Pattern Testing

To perform the pattern testing , previous defects are analyzed. It determines the cause of the failure by looking into the code. Analysis template includes reasons for the defect. This helps test cases designed as they are proactive in finding other failures before hitting production.

3. Orthogonal Array Testing

Orthogonal Array Testing is a black box testing technique. In orthogonal array testing, test data have n numbers of permutations and combinations. Orthogonal array testing is preferred when maximum coverage is required when there are very few test cases and test data is large. This is very helpful in testing complex applications.

4. Regression Testing

Regression Testing is testing the software after every change in the software to make sure that the changes or the new functionalities are not affecting the existing functioning of the system. Regression testing is also carried out to ensure that fixing any defect has not impacted other functionality of the software.

5. State transition Testing

State Transition Testing is frequently applied to systems that display various states while they are being operated. Testers who have just a limited understanding of the internal states create test cases with the intention of making sure that state transitions are handled correctly.

6. Testing Decision Tables

Decision tables are a useful tool for organizing and condensing complicated business rules and reasoning. Decision tables are used by testers with limited understanding to generate test cases covering multiple combinations of input conditions and expected results.

7. Testing APIs

Even though the main code is not entirely known, gray box testing, also known as API (Application Programming Interface) Testing , focuses on testing the system’s exposed interfaces. The main goal of testing is to make sure the API accepts various input formats and operates as intended.

8. Data Flow Testing

Analyzing the Flow of Data Testing through the system forms the basis of data flow testing. Partial knowledge testers create test cases that examine the data’s pathways throughout the application, assisting in the identification of possible problems with handling and processing the data.

Process of Gray Box Testing

Gray box testing mix the both black box and white box testing. The tester has partial knowledge of how the system works internally but focuses mainly on its inputs and outputs. Unlike white box testing, you don’t need to design tests based on the code. Instead, you combine insights from both external and internal perspectives to guide the testing process.

1. Identify Inputs

First, look at the system and decide which inputs you need for testing. This can be done using black box testing (looking at the system from the outside) and white box testing (understanding some of the internal structure). By combining both, you get a clearer idea of what inputs are essential for testing the system.

2. Predict Outputs

Once you know the inputs, think about what the expected results (outputs) should be. This helps in understanding whether the system will behave as expected when given the right inputs.

3. Select Key Testing Paths

Next, focus on the most important parts of the system that need testing. Think about the key features and how they work both internally (the system’s code and structure) and externally (how users interact with the system). These are the paths you should test first.

4. Spot Sub-Functions

Look at smaller parts or features within the system that may need extra attention. These could be small components that play a big role but may get overlooked if not specifically tested.

5. Identify Inputs for Sub-Functions

Once you’ve spotted these smaller sub-functions, figure out the exact inputs that will test them properly. These inputs should be carefully chosen to make sure the sub-functions work as they should.

6. Predict Expected Outputs for Sub-Functions

After identifying the inputs for the sub-functions, predict what the output should be. This helps you understand what results you’re expecting from these smaller features when the right inputs are applied.

7. Run Sub-Function Test Cases

Now, test the sub-functions by applying real-world inputs and conditions. You’ll want to see if these sub-functions handle the inputs correctly and behave as expected in real scenarios.

8. Verify the Results

Once the tests are run, compare the actual results to the expected outputs. If the actual results match the predicted ones, that means everything is working as it should. If not, you can identify where things went wrong.

9. Repeat Steps 4-8

Testing not stop after doing one time only, test other sub-functions and paths that may not have been fully tested the first time. This ensures every part of the system is well-tested.

10. Refine and Repeat

After testing, you may find some issues or areas that need improvement. Keep refining your test cases, test again, and keep adjusting based on the results. This ensures the system is thoroughly tested and works as expected.

Grey Box Testing Example

To better understand how gray box testing works by combining elements of both white box and black box testing, let’s take an example of a User Registration System.

ArtOfTesting's login functionality include gray box testing and the user interface (UI) and the backend systems are functioning as expected. This type of testing combines knowledge of the system’s internal workings (like the API, database, and user authentication logic) with external user-facing behavior.

Steps:

Navigate to the Login Page: Open the login page URL using Selenium.
Fill in Username: Enter a valid username (e.g., auth_user) into the username field.
Fill in Password: Enter the correct password (e.g., auth_password) into the password field.
Click on Login Button: Simulate a click on the login button.
Verify Successful Login: Ensure that the user is redirected to the correct page after logging in.
Database Check (Optional): Check the database to ensure that the login attempt was recorded in the user login table.
API Verification (Optional): Verify the login API response to ensure it returns the correct status and session information.

BaseTestMain.java

Java

package Test;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.AfterMethod;
import org.testng.annotations.BeforeMethod;

public class BaseTestMain {

    protected WebDriver driver;
    protected String Url = "https://ecommerce.artoftesting.com/";

    // Set up the ChromeDriver
    @BeforeMethod
    public void setup() {
        // Set the path to your chromedriver executable
        System.setProperty("webdriver.chrome.driver", "C:\\Users\\path of the chromedriver\\drivers\\chromedriver.exe");
        
        
        // Initialize the ChromeDriver
        driver = new ChromeDriver();
    }

    // Close the browser after each test
    @AfterMethod
    public void teardown() {
        if (driver != null) {
            driver.quit();
        }
    }
}

LoginPage.java

Java

package ArtOfTesting;

import org.openqa.selenium.By;
import org.testng.Assert;
import org.testng.annotations.Test;

import Test.BaseTestMain;

public class LoginPageTest extends BaseTestMain{
	
	@Test
	public void TestLogin() {
		driver.get(Url);
		driver.findElement(By.name("uname")).clear();
		driver.findElement(By.name("uname")).sendKeys("auth_user");
		
		Assert.assertEquals(driver.getCurrentUrl(), "https://ecommerce.artoftesting.com/");
		
		driver.findElement(By.name("pass")).clear();
		driver.findElement(By.name("pass")).sendKeys("auth_password");
		
		driver.findElement(By.className("Login_btn__pALc8")).click();
		System.out.println("Login Succesfull");
		
		 // Optional: Backend Verification - Database Check
        // For this step, you could verify the database to ensure the login attempt was logged.
        // Example (pseudo-code for DB verification, not actual code in the test):
        // assertTrue(checkDatabaseForLoginAttempt("auth_user"));

        // Optional: API Verification - Verify API response (you can use Postman or other API testing tools for this)
        // Example (pseudo-code for API verification):
        // assertTrue(verifyLoginApiResponse("auth_user"))
		
	}

}

Output:

Gray Box Testing Tools

Here are the some of tools which includes in the process of gray box testing:

1. Selenium

Selenium tool automates web application tests and supports multiple browsers, making it ideal for testing web apps across different environments. It helps testers verify the functionality and user experience of web applications efficiently.

2. Appium

Appium tool is used for automating mobile application tests. Appium allows testers to test both Android and iOS apps, ensuring they function correctly across various mobile platforms.

3. Postman

Postman is widely used for API testing. It allows testers to send API requests and check the responses, making it essential for verifying the functionality and reliability of the backend of applications.

4. JUnit and NUnit

JUnit and NUnit are Unit testing frameworks for Java and .NET applications, respectively. They help in validating individual components of the code during gray box testing, ensuring specific parts of the software function as expected.

5. Burp Suite

Burp Suite is a powerful security testing tool for web applications. Burp Suite analyzes network traffic and helps identify potential vulnerabilities, making it valuable for gray box testing to ensure the application’s security.

6. Chrome DevTools

Chrome DevTools are Built-in browser tools that assist testers in inspecting web pages, debugging JavaScript, and logging network activity. They provide valuable insights into the technical performance of web applications during gray box testing.

Difference between Black Box Testing and Gray Box Testing

Gray box testing is a combination of black box and white box testing, and can provide a more comprehensive testing approach than black box testing alone. The choice of testing approach depends on the testing objectives, the testing stage, and the available resources.

Here is a simple comparison of them in which highlighting key aspects:

Black Box Testing	Gray Box Testing
It is a software testing technique in which the tester doesn’t know the internal structure of the application being tested.	It is a software testing technique in which the tester partially know the internal structure of the application being tested.
It is known as closed box testing.	It is known as translucent testing.
No knowledge of implementation is required.	Knowledge of implementation is required but need not to be expert.
It is based on external expectations and outer behavior of the software.	It is based on database diagrams and data flow diagrams.
It is less time consuming.	It is time consuming but not too much.

Read More: Black Box Testing vs Gray Box Testing

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