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Ch8.Testing

Software Testing Overview

  • Software testing is essential for ensuring programs function as intended and to find defects before deployment.

  • Testing reveals errors but does not guarantee their absence.

  • It forms part of a broader verification and validation (V&V) process including static validation methods.

Goals of Program Testing

Development Objectives

  • Demonstrate to both developer and customer that software meets requirements.

    • Each requirement in a custom software project should have corresponding test cases.

    • For generic software, tests should cover all features and their combinations.

  • Identify incorrect, undesirable system behaviors.

    • Focused on defect testing, which seeks to find operational failures like crashes and data issues.

Testing Types

Validation vs. Defect Testing

  • Validation Testing: Ensures the system performs as expected with given test cases reflecting real usage.

  • Defect Testing: Uses obscure test cases to expose defects, which may not reflect typical system use.

Testing Processes

Goals

  • Validation Testing: Validate that software meets requirements.

    • Successful tests demonstrate intended system operation.

  • Defect Testing: Identify faults or discrepancies in software behavior.

    • Successful tests highlight incorrect operations exposing defects.

Input-Output Testing Model

  • Inputs are artificial data used in testing.

  • Outputs reveal whether defects exist based on the program's response to the tests.

Verification and Validation (V&V)

Definitions

  • Verification: Ensures the product is built correctly, conforming to specifications.

  • Validation: Confirms the product meets user needs and intended use.

V&V Confidence Levels

  • Confidence in a system's fitness is influenced by:

    • Software criticality.

    • User expectations.

    • Marketing urgency overriding defect discovery.

Inspections and Testing

Inspections

  • Focus on analyzing static representations to detect defects before implementation.

  • Effective for catching errors without execution.

Testing

  • Dynamic verification through system execution with test data.

  • Allows for observation of operational behavior.

Benefits of Inspections

  • Inspecting uncover hidden errors not visible during testing.

  • Incomplete systems can be analyzed without requiring extensive test setups.

  • Inspections can also assess broader quality attributes beyond just defect detection.

Software Testing Process

Stages

  • Development testing

    • Includes unit, component, and system testing to find bugs early in development.

  • Release testing

    • Conducted by separate teams on fully integrated systems before user release.

  • User testing

    • Involves actual users testing software in real work environments.

Unit Testing

Definition

  • Tests individual components or units of code in isolation.

  • Primarily focuses on defect tests for:

    • Functions or methods.

    • Complete object classes.

Object Class Testing

  • Full coverage requires testing all operations, attributes, and states of an object class.

  • Complex due to inheritance and object interactions.

Automated Testing

Features

  • Automating unit tests with frameworks like JUnit enhances efficiency.

  • Helps track code changes and maintain test coverage.

Choosing Unit Test Cases

  • Tests must reflect both normal and abnormal use cases.

  • Focus on inputs that are expected to succeed and those that could expose defects.

Testing Strategies

Key Techniques

  • Partition testing groups similar inputs into equivalence partitions for testing.

  • Use guideline-based testing from prior error experiences to choose test cases.

Component Testing

  • Tests composed of multiple interacting components to validate interface behaviors.

Interface Testing

Objectives

  • Catch faults from interface errors or misunderstandings.

  • Test parameter, shared memory, procedural, and message passing interfaces.

Potential Interface Errors

  • Common issues include misuse, misunderstanding, and timing errors.

System Testing

Focus Areas

  • System testing integrates various components to test interactions and data transfers.

  • Checks the emergent behavior of the system as a whole rather than individual units.

User Testing

Importance

  • Direct input from users is essential in validating reliability and usability not replicable in controlled tests.

Types

  • Alpha Testing: Conducted at the development site.

  • Beta Testing: Software released for user experimentation.

  • Acceptance Testing: Customers validate readiness for use in their environment.

Test-Driven Development (TDD)

Process Overview

  • Write tests prior to developing code, following an incremental development approach.

  • Ensures each piece of functionality is continuously validated against testing criteria.

Benefits

  • Guarantees code coverage and simplifies the debugging process.

  • Provides documentation through tests that state intended functionality.

Key Testing Principles

  • Acknowledge that testing can confirm errors exist but not that no errors remain.

  • Automation and consistent re-testing are crucial for effective software development and validation.