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Automated Test Oracles in Software Testing

February 12, 2025
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Test Oracles
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Recent advances in automatic test case generation and new tools have motivated the development of efficient test oracles. The future belongs to these oracles who speak in ones and zeros, blurring the line between human and machine judgment to create the perfect software. 

In this blog, let us see how! First of all, you should know what Test Oracles are……

What are Test Oracles?

Test oracles, the gatekeepers of software quality, are likewise judges, pronouncing the correctness of a system’s output.

Test oracles are a mechanism used in software testing to determine whether the output produced by the system under test is correct. Test oracles are rules we devise early to say what we expect the system to do. 

There are two test oracles: “manual” ones, which people make based on their knowledge, and “automated” ones, which use computer code to decide if the system is doing the right thing. 

Test oracles are super important because they help us ensure the software we’re testing is accurate, reliable, and working properly.

Types of Test Oracles

Imagine you’re a software tester, the ultimate skeptic. You’ve built this awesome app, but how do you know it’s not just spitting out gibberish?

That’s where test oracles come in – they’re like the analysts of the software world, deciding if your creation is worthy.

Two main types:

Human Judgment: 

Think of your grandma testing your new recipe. She doesn’t need a fancy scale, just her taste buds and years of experience. 

Same with human oracles – 

  • It is based on the assessment of human testers. 
  • Involves human intuition, experience, and domain knowledge.
  • Subjective and may vary based on individual tester expertise.

Automated Oracles: 

These guys are the robots of the bunch, using algorithms and pre-defined rules to check your app. Think of it as a checklist – if everything checks out, you’re golden.

  • It relies on algorithms and automated processes.
  • Utilizes predefined rules and criteria to assess correctness.
  • Reduces dependence on human judgment, enhancing consistency.

But it’s not just black and white: There are more!

Comparison Oracles: 

These guys compare your app’s output to a pre-written answer key, like grading a test.

  • Compares the actual output of the program with an expected output.
  • Requires predefined expected results to determine correctness.
  • Commonly used in functional testing.

Differential Oracles: 

They’re like detectives, comparing different versions of your app to make sure nothing funky changes.

  • Compares the output of two different versions of the same program.
  • Identifies discrepancies between versions to ensure consistency.

And there’s more! 

From “lucky guessers” using statistics to “time cops” ensuring speed, there’s an oracle for every software quirk. Here are a few……….

Stochastic Oracles:

  • Employs statistical methods to determine correctness.
  • Takes into account probabilities and random sampling.
  • It helps assess system behavior under varying conditions.

Temporal Oracles:

  • Considers the timing aspects of the system’s behavior.
  • Ensures that the program produces correct outputs within specified time constraints.
  • Important for real-time and time-sensitive applications.

Inference Oracles:

  • Derives expected results based on inferred system behavior.
  • Analyzes the program’s logic and specifications to make predictions.
  • Requires a deep understanding of the software’s design and requirements.

Operational Profile Oracles:

  • Considers the operational environment and usage patterns.
  • Determines correctness based on how the system performs in real-world scenarios.
  • It helps identify issues that may arise in specific usage conditions.

Metamorphic Oracles:

  • Defines relationships between input and output transformations.
  • Validates correctness by examining the transformed outputs.
  • It is particularly useful when exact expected outputs are challenging to determine.

Knowledge-Based Oracles:

  • Relies on expert knowledge and documentation.
  • Assesses correctness based on compliance with established guidelines.
  • Suitable for systems where explicit rules and standards exist.

These test oracles use various methods and standards to ensure software systems are correct.

The Importance of Test Oracles

Let me give you some essential points:

  • Verifying Software Behavior: Test oracles are the ultimate truth against which software behavior is compared. They ensure the outputs from your tests accurately reflect the expected or desired functionality.
  • Uncovering Defects: By comparing actual results with the oracle’s definition of correctness, you can identify discrepancies and pinpoint bugs hidden within your code.
  • Confidence in Quality: Reliable oracles enhance your confidence in the software’s quality by providing a clear and objective measure of its performance against requirements.
  • Diverse Testing Coverage: Different types of oracles, like equivalence partitioning or decision tables, can help explore various scenarios and edge cases, leading to more comprehensive testing.
  • Improved Development Process: Effective oracles foster a feedback loop between testing and development, enabling faster defect resolution and better product iterations.
  • Automated Testing Efficiency: With clearly defined oracles, you can automate test execution and analysis, saving time and resources while maintaining consistent quality checks.
  • Documentation and Communication: Oracles serve as documentation, clearly communicating the expected behavior to developers, testers, and other stakeholders.

By prioritizing and implementing robust test oracles, you can elevate your software quality, build trust in its functionality, and streamline your development process for success.

Test Oracle Process

The Test Oracle process is a crucial step in software testing that involves defining the expected outcome of a test case before actually running it. It acts as a benchmark against which the test results are compared, enabling testers to determine whether a test case has passed or failed accurately.

Here’s how the Test Oracle process typically unfolds:

Step 1: Define the Test Case:

  • Identify the specific functionality or feature being tested.
  • Formulate the test case scenario, including input data, pre-conditions, and expected user actions.

Step 2: Predict the Expected Outcome:

  • Based on the test case scenario and the software’s expected behavior, explicitly define the expected output or outcome. This could be:
    • Specific data values or screen displays.
    • System behavior or response to user actions.
    • Error messages or notifications.

Step 3: Document the Expected Outcome:

  • Clearly document the expected outcome in the test case documentation. This could include:
    • Screenshots of expected screens or outputs.
    • Log files or data values.
    • Expected error messages or system behavior.

Step 4: Run the Test Case:

  • Execute the test case according to the defined scenario.

Step 5: Compare Actual vs. Expected Outcome:

  • After running the test, compare the actual results with the expected outcomes previously defined.

Step 6: Determine Pass/Fail:

  • Based on the comparison, determine whether the test case passed or failed:
    • Pass: If the actual results match the expected outcomes in all aspects.
    • Fail: If any discrepancy exists between the actual and expected outcomes.

Step 7: Analyze Discrepancies (if any):

  • If the test case fails, analyze the discrepancy to understand the cause. This could involve:
    • Reviewing logs or error messages.
    • Rerunning the test with different data or environments.
    • Consulting with developers or other testers.

Step 8: Update Test Case (if necessary):

  • If the discrepancy reveals an issue with the software, update the test case to reflect the actual behavior.
  • Alternatively, update the documentation to reflect the actual expected behavior if the outcome is incorrect.

Why to use Test Oracles

  • Improved Accuracy: By defining expected outcomes beforehand, you avoid ambiguity and subjective interpretations of test results, leading to more accurate pass/fail determinations.
  • Enhanced Efficiency: Comparing actual results to pre-defined oracles is quicker than manually analyzing outputs, saving time and effort during testing.
  • Better Defect Detection: Clear oracles help identify even subtle discrepancies, increasing the chances of catching subtle bugs and edge cases.
  • More robust Test Case Design: Defining oracles forces you to consider all possible outcomes, leading to more comprehensive and robust test cases.
  • Documentation and Communication: Documented oracles provide a precise reference point for developers and other testers, improving communication and collaboration.

How to Use Test Oracles?

Here I will provide a valuable roadmap for you to implement and leverage Test Oracles effectively in software testing practices.

Define Expected Outcomes: 

It is essential to define the expected outcomes for each test case clearly. This includes both positive and negative scenarios to ensure comprehensive testing.

Create Test Cases:

Develop test cases encompassing a range of inputs and conditions to thoroughly test the system’s functionality.

Identify Oracle Sources:

Determine the information sources for your test oracle, such as requirements documents, design specs, or previous software versions.

Implement Oracle Mechanism:

Establish a mechanism for comparing actual outcomes to expected outcomes. This could involve writing assertions in automated test scripts or creating manual checklists.

Execute Tests:

Run the tests against the system under test, allowing the oracle to compare actual outcomes with the predefined expected results.

Analyze Results:

Analyze the test results, investigating any discrepancies between the actual and expected outcomes, including the root causes of failures.

Document Findings:

Documenting testing results and highlighting deviations from the expected outcomes is essential. The information should be clear and actionable for developers to address any issues.

Iterative Improvement:

Iteratively use test results feedback to improve test cases and the oracle to enhance the testing process’s robustness.

Regression Testing:

Add test oracle to regression testing to verify expected outcomes after changes.

Review and Update:

Update test oracles regularly to align with changes in requirements and the system’s behavior.

Manual and Automated Test Oracle

Here is a table to explain in detail about these two:

FeatureManual Test OracleAutomated Test Oracle
DefinitionThe expected outcome is defined and compared manually by the tester.Expected outcomes are defined and compared automatically by the testing tool.
ImplementationChecklists, screenshots, manual data comparisons.Assertions in code, code oracles, and external data sources.
AdvantagesFlexible for complex scenarios and edge cases.
 Easier to implement for simple tests. 
 Requires less technical expertise.
Faster and more efficient for repetitive tests. 
Reduces human error in comparison. 
Can integrate with CI/CD pipelines.
DisadvantagesTime-consuming and prone to human error. 
Need help to maintain large test suites. 
Less efficient for repetitive tests.
Requires technical expertise to implement and maintain. 
It may be brittle and break with code changes. 
Limited flexibility for complex scenarios.
ExamplesVerifying a login form displays a success message after entering the correct credentials. 
Manually compare downloaded files with the expected size and checksum.
Using assertions in code to check if a button click triggers the desired action.
 Querying an external database for expected data and comparing it with test results.

Check here – Database Testing

Automated Test Oracles 

Automated Test Oracles are essential in modern software testing as they can automatically compare actual test results with pre-defined expected outcomes. 

An Automated Test Oracle compares the actual test results with the pre-defined expected outcomes, providing developers with a reliable and accurate way to validate their software applications.

This eliminates the need for manual intervention and reduces the risk of human error, improving efficiency, accuracy, and consistency in the testing process.

By automating the testing process, Automated Test Oracles eliminates the need for manual intervention, which can be 

  • time-consuming, 
  • error-prone, and 
  • costly.

Besides, automated testing with Test Oracles reduces the risk of human error and increases consistency in the testing process.

I take an example from Testsigma, an advanced cloud-based automation testing solution, to show you how this can be done. 

Let’s consider a simple test case in Testsigma aimed at verifying the login functionality of a web application:

Test Case: Login with Valid Credentials

Steps:

  1. Open the login page. (for example, we have taken simply travel website)
  2. Enter a valid username.
  3. Enter a valid password.
  4. Click the “Login” button.

Expected Outcome:

  • The user should be successfully logged in.
  • The homepage should be displayed.
  • The username should be displayed in the header section.

The below image shows the “test cases” and “passed” test results.

Test cases

Assertions within Test Steps:

  • Step 8: After clicking “SelectFrom”, use an assertion to verify the dropdown menu is open and “Los Angeles” is displayed as the default option.
  • Step 11: After clicking “SelectTo”, use an assertion to check if “New York City” is displayed as the selected option.
  • Step 12: After clicking “Search Flights”, use an assertion to confirm the results page is loaded and contains elements like flight listings, departure/arrival cities, dates, and prices.

    You can verify specific elements or patterns within the page structure.

This image shows the implementation of the Automated Test Oracles function:

Test Oracles

Benefits of Testsigma:

  • Improved Accuracy: Assertions eliminate the risk of manual interpretation errors in verifying the expected outcome.
  • Faster Execution: Testsigma automatically executes the assertions after each step, providing immediate feedback if any step fails.
  • Enhanced Reusability: Build reusable functions or assertion libraries for commonly used validation checks.
  • CI/CD Integration: Testsigma readily integrates with CI/CD pipelines, enabling automated checks on each build with accurate oracles.

Automate your end-to-end UI tests for web, mobile and desktop applications, with in-built oracles, with Testsigma

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Summary

To summarize, Automated Test Oracles have entirely transformed the software development game. They give developers a dependable, precise, and speedy way to ensure their apps are thoroughly tested and completely error-free.

Frequently Asked Questions

What is test oracle in Istqb?

“Test Oracle” in ISTQB refers to a technique for identifying faults in software by comparing expected outputs with actual ones, showing disparities. It’s not a specific tool but a testing approach.

Written By

Kiruthika Devaraj

Testsigma Author - Kiruthika Devaraj

Kiruthika Devaraj

The author is a proficient and passionate writer who takes great pleasure in captivating readers with her imaginative writing. Her unique ability to craft engaging write-ups, stories, and poems transports readers into the fascinating world of her characters. With several published novels, short stories, poems, blogs, and articles, she continuously explores new ways to express her creativity. If you want to establish a professional connection with this talented author, we encourage you to send a connection request on LinkedIn.

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