Precondition in a Test Case | What is it & How do you use it?

In any real-life activity, the events leading up to an event determine the outcome. A test case is like a recipe – it needs the right ingredients and steps to produce the desired outcome. Preconditions are those required ingredients. 

They outline the specific conditions that must be met before you run the test. Think of them as setting the stage for your test. Ensuring these preconditions are in place guarantees a reliable and meaningful test run.

What is preconditioning in testing?

Preconditions are the conditions that must be fulfilled to ensure the test runs smoothly and produces reliable and accurate results. 

Preconditioning helps set up the test environment, data, and other necessary parameters before running the test. By ensuring that the preconditions are met, testers can minimize the chances of encountering errors and inconsistencies during the test run. 

Yet, preconditioning helps to ensure that the testing process is efficient, effective and produces the desired results.

Here’s a different real-life example to illustrate preconditions:

Imagine you’re baking a cake. The main activity is mixing the batter and putting it in the oven.

Yet, several preconditions need to be met before you can even begin:

1. You must have all the necessary ingredients, like flour, sugar, and eggs.
2. You’ll need a working oven at the proper temperature.
3. You’ll want a mixing bowl and utensils ready for action.

 With these preconditions in place, attempting to bake the cake is possible.

How do you write preconditions in test cases?

Here’s how to incorporate strong preconditions into your test cases:

• Identify Requirements:  Clearly define the initial state the system needs to be in for the test to run correctly. This might involve data setup, user permissions, or system configurations.
  
• List Explicit Steps (if necessary):  If achieving the preconditions requires specific actions, list them as separate steps within your test case. This enhances clarity and ensures everyone understands the necessary setup process.
  
• Consider Reusability:  If preconditions are common across multiple tests, explore creating separate reusable steps or functions to streamline your test suite and avoid redundancy.

What are the preconditions that are essential for successful test execution?

Guaranteeing successful test execution hinges on establishing strong preconditions. Here are some key elements to consider:

• Proper Environment:  Ensure the test environment (hardware, software, network) is set up correctly and matches the production environment as closely as possible.
  
• Data Availability:  Verify that all necessary test data in the system is present and accurate, before running the test. This might involve creating specific test accounts or populating databases with relevant information.
  
• System State:  The system under test should be in a specific, well-defined state. This could involve closing open applications, logging out user accounts, or setting specific system configurations.
  
• Dependencies Met:  If the test case relies on the successful execution of other tests, ensure those pre-requisite tests have passed before proceeding.

How to Use Preconditions in Test Cases?

Preconditions are the building blocks of robust test cases. By clearly defining them, you ensure your tests start from a consistent state, leading to more reliable results. Using a real-world example in Testsigma, an automated testing tool, let’s see how preconditions work. 

In Testsigma, you can define this precondition directly within your test case steps. 

This is just a sample example

Here’s how it will look:

Precondition: I take an example to verify that a user is able to login to gmail. 

In Testsigma, you can define this precondition as a separate step within your test case. This step might involve navigating to the Gmail login page using a specific URL (e.g., “https://accounts.google.com”). Testsigma would then check if the login page elements are present, indicating a successful precondition.

This precondition ensures your test case starts with a clean slate, where the user is demonstrably logged out. If the verification step fails, the precondition isn’t met, and the test case won’t proceed. 

This safeguards against unreliable test results and ensures your test focuses solely on the login functionality for a specific user. 

Only if this precondition is met (i.e., you’re on the login page) will Testsigma proceed with the actual test steps, which might involve entering your username and password and verifying a successful login.

This approach ensures your test starts from a known state (logged out) and focuses specifically on the login functionality. In the image below, you can see the preconditions passed. Next, you will find your test cases for the Gmail login page. 

Yet, if the precondition fails (perhaps you were already logged in), the entire test case fails, indicating the test couldn’t be executed under the intended conditions.

Once you’ve defined the precondition, you can link it to the login test steps. Testsigma will execute the precondition first. If the precondition (logging out) is successful, the test proceeds with the login steps, as shown in the below image. 

This approach ensures your login test always starts with a clean slate (logged-out state) and delivers reliable results about the login functionality itself. By effectively using preconditions in Testsigma, you can create robust test cases more likely to catch actual issues.

This approach ensures your tests are reliable and provide clear insights into the actual login process.

Analyzing the Results of a Test Case Using Preconditions

Preconditions play a vital role in analyzing test case results. Examining the preconditions is a crucial first step if a test case fails. 

Did the preconditions ensure the system was in the expected state?  

For example, in the previous section, we saw that verifying if the user was indeed logged out beforehand (as per the precondition) is essential if a login test fails.  

By analyzing preconditions first, you can isolate issues and determine if the test failure stems from problems with the preconditions or the actual functionality being tested. This focused approach saves time and ensures you’re addressing the root cause of the failure.

Conclusion

In conclusion, preconditions are the cornerstone of effective software testing. They establish a well-defined foundation for test cases, ensuring consistent execution and reliable results. By understanding how to write and utilize preconditions in tools like Testsigma, you can streamline your testing process, improve test maintainability, and ultimately deliver higher-quality software. 

Remember, clear preconditions are like a strong foundation for your house – they pave the way for robust and trustworthy testing practices.

Happy Testing!

Frequently Asked Questions

What is “Post-condition” in a test case?

In a test case, a post-condition refers to the state or conditions that are expected to be true after the execution of the test scenario. These conditions specify the expected outcomes or changes in the system after the test.

What is the difference between precondition and postcondition in a test case?

Preconditions specify the initial state or conditions required for executing a test, while postconditions define the expected outcomes or states after the test execution. Preconditions ensure proper test setup, while postconditions verify the correctness and effectiveness of the tested functionality.