Checking exception type hierarchy in JUnit - Framework Patterns

Framework Mode - Checking exception type hierarchy

Folder Structure

project-root/
├── src/
│   ├── main/
│   │   └── java/
│   │       └── com/example/app/
│   │           └── (application code)
│   └── test/
│       └── java/
│           └── com/example/app/
│               ├── exceptions/       <-- custom exception classes
│               ├── utils/            <-- helper classes for tests
│               └── tests/            <-- JUnit test classes
│                   └── ExceptionHierarchyTest.java
├── pom.xml                        <-- Maven build and dependencies
└── README.md
    

Test Framework Layers

• Exception Classes Layer: Custom exceptions organized by hierarchy in exceptions/.
• Test Classes Layer: JUnit test classes in tests/ that verify exception types and hierarchy.
• Utility Layer: Helper methods for exception assertions or reflection in utils/.
• Configuration Layer: Maven or Gradle config files managing dependencies and test execution.

Configuration Patterns

• Use pom.xml to manage JUnit 5 dependency and build lifecycle.
• Configure test execution profiles for different environments if needed (e.g., CI vs local).
• Use system properties or environment variables to toggle verbose exception logging.
• Keep exception class package structure consistent for easy import and maintenance.

Test Reporting and CI/CD Integration

• JUnit generates XML and HTML reports by default for test results.
• Integrate with CI tools like Jenkins, GitHub Actions, or GitLab CI to run tests on each commit.
• Fail build if exception hierarchy tests fail to ensure exception contracts are maintained.
• Use test reports to quickly identify if wrong exception types are thrown or hierarchy is broken.

Best Practices

• Organize custom exceptions in a clear hierarchy reflecting their relationships.
• Write tests that assert not only exception thrown but also its exact type or superclass.
• Use assertThrows in JUnit 5 to check for expected exceptions precisely.
• Keep exception tests isolated and focused on one exception type or hierarchy branch per test.
• Document exception hierarchy in code and tests for maintainability and clarity.

Self Check

Where in this folder structure would you add a new test class to verify that a newly created custom exception correctly extends the base exception?

Key Result

Organize exception classes and write focused JUnit tests to verify exception type hierarchy using assertThrows.