Debugging and Testing in Eiffel Programming Language

Leave a Comment / Electronics Technology / By Srikanta Paital

//piembsystech.com/eiffel-language/" target="_blank" rel="noreferrer noopener">Eiffel programming language, these practices are enriched by numerous tools and methodologies which make use of its specificities. Herein, Eiffel’s mechanisms of debugging and testing are introduced together with best practices.

Introduction to Debugging and Testing in Eiffel Programming Language

Debugging means the process of locating, analyzing and fixing errors or bugs in a program. In Eiffel, debugging is made easier because of several powerful tools and a few language features.

Debugging Tools in Eiffel

EiffelStudio Debugger: EiffelStudio is the main integrated environment for programming in Eiffel. It has an integrated debugger that includes breakpoints, step executions, and inspection of variables. You are allowed to set breakpoints in your code where you want to stop the execution; by doing so, you can then inspect the state at a particular point in time. Step execution lets you follow the program flow, while variable inspection allows you to probe into various variable values at runtime.
Eiffel debugging commands: EiffelStudio also has available a set of debugging commands through the command line or console of a debugger. These commands provide you with basic control over the execution, inspection of call stacks, and runtime data analysis.

Error Reporting and Analysis

Eiffel comes with outstanding error reporting and analyzing functionalities. The language is designed to enable the facility of writing reliable code based on the concept of a contract: precondition, postcondition, and invariant. For whatever, if any, violation of those contracts Eiffel creates an exception with the full report of the error showing the place and type of violation. This debugging message points the programmer directly to the origin of the problem.

Introduction to Testing in Eiffel

Testing is the process of validating that a program behaves as expected. Eiffel’s approach to testing is closely tied to its design by contract principles, which enhance code reliability and maintainability.

Unit Testing with Eiffel

• EiffelTest Framework: EiffelTest is a unit testing framework designed specifically for Eiffel. It allows developers to write and execute test cases for individual units of code. EiffelTest integrates seamlessly with EiffelStudio, providing a user-friendly interface for running tests and viewing results. Test cases can be written as separate classes that inherit from the TEST_CASE class, and you can define various assertions to verify the correctness of your code.
• Assertions and Contracts: Eiffel’s design by contract methodology plays a crucial role in testing. Contracts—preconditions, postconditions, and invariants—serve as a formal specification of a class’s behavior. By defining these contracts, you establish the expected behavior of your code, making it easier to write tests that ensure these expectations are met.

Automated Testing and Continuous Integration

Automated testing is a key component of modern software development practices. In Eiffel, you can automate your tests using the EiffelTest framework and integrate them into a continuous integration (CI) pipeline. This integration ensures that tests are run automatically whenever changes are made to the codebase, helping to catch issues early in the development process.

Why we Debugging and Testing in Eiffel Programming Language?

Debugging and testing are crucial activities in software development, and they play a significant role in the Eiffel programming language due to several reasons tied to its unique features and goals. Here’s why debugging and testing are so important in Eiffel:

1. Ensuring Code Quality and Reliability

1.1. Design by Contract Eiffel’s hallmark is its design by contract (DbC) methodology, which involves specifying formal agreements between software components. These contracts include preconditions, postconditions, and invariants that define the expected behavior of the code. Debugging and testing are essential to ensure that these contracts are correctly implemented and upheld, thereby guaranteeing code quality and reliability.

1.2. Error Prevention Debugging helps identify and fix errors early in the development process. In Eiffel, contracts serve as a safety net, but without thorough debugging, developers might overlook issues that could lead to contract violations or unintended behaviors. Testing complements this by validating that the code behaves as expected in various scenarios.

2. Facilitating Correctness and Maintainability

2.1. Automated Testing Eiffel promotes automated testing through frameworks like EiffelTest. Automated tests can be run regularly to check that the code behaves correctly and adheres to the contracts. This ongoing validation helps maintain code correctness as the software evolves and changes over time.

2.2. Documentation Through Contracts Contracts act as documentation for the intended behavior of software components. When debugging, these contracts help pinpoint where the code deviates from its expected behavior. Testing ensures that these documented expectations are met, making the codebase more maintainable and understandable.

3. Enhancing Developer Productivity

3.1. Efficient Issue Resolution Effective debugging tools, such as those provided by EiffelStudio, enable developers to quickly identify and resolve issues. By using breakpoints, step execution, and variable inspection, developers can efficiently track down the root cause of problems, saving time and effort.

3.2. Reducing Regression Issues Testing, especially when integrated into a continuous integration (CI) pipeline, helps catch regressions early. As new features are added or existing ones are modified, automated tests ensure that previously working functionality remains intact, reducing the risk of introducing new bugs.

4. Supporting Robust Software Design

4.1. Contract Violation Detection In Eiffel, contracts are used to specify what is expected from a software component. Debugging tools help detect contract violations at runtime, providing immediate feedback on where and why the code failed to meet its specifications.

4.2. Improved Reliability Thorough testing and debugging practices contribute to the overall reliability of the software. By verifying that the code adheres to its contracts and performs as intended under various conditions, developers can build more robust and dependable applications.

5. Encouraging Best Practices

5.1. Consistent Quality Assurance Incorporating debugging and testing into the development workflow enforces best practices in software engineering. These practices ensure that code quality is consistently monitored and maintained, leading to higher standards in software development.

5.2. Iterative Improvement Debugging and testing foster an environment of continuous improvement. By regularly testing and debugging, developers can iteratively refine their code, address issues, and enhance the overall quality of the software.

Example of Debugging and Testing in Eiffel Programming Language

We’ll create a simple class in Eiffel that performs basic arithmetic operations. We will then show how to debug issues with this class and write tests to ensure its correctness.

1. Creating the Class

Let’s define a class CALCULATOR with basic arithmetic operations: addition, subtraction, multiplication, and division. We will also include contracts (preconditions and postconditions) to specify the expected behavior.

class
    CALCULATOR

create
    make

feature -- Initialization

    make
        -- Initialization procedure.
        do
            -- No specific initialization needed for this example.
        end

feature -- Basic Operations

    add (a, b: INTEGER): INTEGER
        require
            a >= 0 and b >= 0
        do
            Result := a + b
        ensure
            Result = a + b
        end

    subtract (a, b: INTEGER): INTEGER
        require
            a >= b
        do
            Result := a - b
        ensure
            Result = a - b
        end

    multiply (a, b: INTEGER): INTEGER
        do
            Result := a * b
        ensure
            Result = a * b
        end

    divide (a, b: INTEGER): INTEGER
        require
            b /= 0
        do
            Result := a / b
        ensure
            Result = a // b
        end

end

2. Debugging the Class

Let’s introduce a bug into the divide feature by forgetting to handle cases where b is zero. We’ll then use debugging techniques to identify and fix the issue.

Buggy Code

    divide (a, b: INTEGER): INTEGER
        require
            b /= 0
        do
            Result := a / b
        ensure
            Result = a // b
        end

Debugging Steps

1. Run the Program: Execute the program with a divisor of zero to see the issue.
2. Use Breakpoints: Set a breakpoint in the divide method to inspect the value of b when the method is called. This helps identify if b is indeed zero at runtime.
3. Inspect Variables: Check the value of b and verify that the division operation is being performed correctly.
4. Analyze Error Report: Eiffel’s error reporting will catch the contract violation when b is zero, indicating where the issue occurred.

Fixing the Bug

To fix the issue, update the divide method to handle the division by zero properly:

    divide (a, b: INTEGER): INTEGER
        require
            b /= 0
        do
            Result := a / b
        ensure
            Result = a // b
        end

3. Testing the Class

We will use the EiffelTest framework to create unit tests for our CALCULATOR class. We will write tests to check if each arithmetic operation performs as expected.

Test Class

class
    TEST_CALCULATOR

create
    make

feature -- Initialization

    make
        local
            calc: CALCULATOR
        do
            create calc
            test_add (calc)
            test_subtract (calc)
            test_multiply (calc)
            test_divide (calc)
        end

feature -- Test Cases

    test_add (calc: CALCULATOR)
        local
            result: INTEGER
        do
            result := calc.add (5, 3)
            assert (result = 8)
        end

    test_subtract (calc: CALCULATOR)
        local
            result: INTEGER
        do
            result := calc.subtract (10, 4)
            assert (result = 6)
        end

    test_multiply (calc: CALCULATOR)
        local
            result: INTEGER
        do
            result := calc.multiply (4, 3)
            assert (result = 12)
        end

    test_divide (calc: CALCULATOR)
        local
            result: INTEGER
        do
            result := calc.divide (9, 3)
            assert (result = 3)
        end

end

Running the Tests

1. Execute Tests: Run the TEST_CALCULATOR class within EiffelStudio to execute the test cases.
2. Verify Results: Check the results to ensure all tests pass. If any test fails, debug the CALCULATOR class to identify and fix the issues.