[Part 6]Error Handling and Exception Handling in TypeScript for Robustness

Introduction

Error handling is crucial in test automation to prevent unexpected failures and improve script stability. This module covers TypeScript’s error-handling techniques, including try-catch blocks, custom error classes, and logging mechanisms.

---

Lesson 1: Understanding Errors and Exceptions in TypeScript

Concept:
Errors can occur at runtime, disrupting test execution. Understanding error types helps in debugging and writing resilient automation scripts.

Key Topics:

• Compile-Time vs. Runtime Errors: Type-related vs. execution-related issues.
• Types of Errors: Syntax errors, reference errors, type errors.
• Handling Unexpected Failures: Using structured error handling.

Example:

try {
    let result = JSON.parse("invalid json");
} catch (error) {
    console.error("Caught an error:", error.message);
}

Pro Tip: Always validate input data to minimize runtime exceptions.

---

Lesson 2: Implementing try-catch Blocks for Graceful Error Handling

Concept:
The try-catch structure allows handling runtime errors without breaking script execution.

Key Topics:

• try Block: Enclosing error-prone code.
• catch Block: Handling exceptions and logging errors.
• finally Block: Executing cleanup operations.
• Nested try-catch: Handling different error scenarios.

Example:

try {
    let response = await fetch("https://api.example.com/data");
    if (!response.ok) throw new Error("API request failed");
} catch (error) {
    console.error("Error detected:", error.message);
} finally {
    console.log("Test execution completed.");
}

Pro Tip: Always include a finally block to ensure resource cleanup after execution.

---

Lesson 3: Throwing and Handling Custom Errors in TypeScript

Concept:
Custom errors provide more meaningful debugging insights and control over error management.

Key Topics:

• Using the throw Statement: Raising specific errors.
• Custom Error Classes: Defining domain-specific errors.
• Error Properties: Leveraging error messages and stack traces.

Example:

class TestFailureError extends Error {
    constructor(testName: string, message: string) {
        super(message);
        this.name = "TestFailureError";
        this.testName = testName;
    }
}

try {
    throw new TestFailureError("Login Test", "Expected output mismatch");
} catch (error) {
    console.error(`${error.name} in ${error.testName}: ${error.message}`);
}

Pro Tip: Custom errors make debugging and reporting more meaningful in large test suites.

---

Lesson 4: Logging and Debugging TypeScript Scripts for Efficient Troubleshooting

Concept:
Logging and debugging techniques help detect, trace, and fix test failures efficiently.

Key Topics:

• Console Methods: console.log(), console.error(), console.warn().
• Debugger Statement: Pausing script execution for inspection.
• Error Logs: Writing logs to external files.
• Using Stack Traces: Understanding error origins.

Example:

console.log("Starting test...");
console.warn("Slow API response detected.");
console.error("Test failed: Unexpected response format.");

Pro Tip: Use structured logging libraries like winston for better log management in CI/CD environments.

---

Conclusion

This module provided insights into handling errors in TypeScript test automation, from managing runtime exceptions to implementing structured logging.

Key Takeaways:

• Use try-catch to handle runtime errors gracefully.
• Implement custom errors for domain-specific failure handling.
• Utilize logging techniques to debug and troubleshoot failures.
• Ensure test scripts are resilient by managing error-prone operations effectively.

What’s Next?
In the next module, we will explore File I/O and Data Persistence in TypeScript for QA Automation, covering reading and writing files, handling CSV and JSON data, and automating file-based tasks.

Visit us at Testamplify | X | Instagram | LinkedIn