Error Testing

Test error handling

IntermediateTopic: Error Handling

JavaScript Error Testing Program

This program helps you to learn the fundamental structure and syntax of JavaScript programming.

// Method 1: Test error throwing
function testErrorThrowing() {
    try {
        throw new Error('Test error');
        return false; // Should not reach here
    } catch (error) {
        return error.message === 'Test error';
    }
}

console.log('Error test:', testErrorThrowing());

// Method 2: Test error types
function testErrorType() {
    try {
        throw new TypeError('Type error');
    } catch (error) {
        return error instanceof TypeError;
    }
}

// Method 3: Mock error scenarios
function createErrorScenario(type) {
    switch (type) {
        case 'network':
            throw new Error('Network error');
        case 'timeout':
            throw new Error('Timeout');
        case 'validation':
            throw new ValidationError('Invalid input');
        default:
            throw new Error('Unknown error');
    }
}

// Method 4: Error assertion helper
function assertError(fn, expectedError) {
    try {
        fn();
        return false; // Should have thrown
    } catch (error) {
        if (expectedError) {
            return error instanceof expectedError;
        }
        return true; // Any error is fine
    }
}

assertError(() => {
    throw new TypeError('Type error');
}, TypeError);

// Method 5: Async error testing
async function testAsyncError() {
    try {
        await Promise.reject(new Error('Async error'));
        return false;
    } catch (error) {
        return error.message === 'Async error';
    }
}

// Method 6: Error boundary testing
function testErrorBoundary(errorBoundary, errorFn) {
    try {
        errorFn();
    } catch (error) {
        errorBoundary.catchError(error, { component: 'TestComponent' });
    }
    return errorBoundary.getErrors().length > 0;
}

// Method 7: Integration error testing
async function testErrorHandling() {
    const scenarios = [
        () => { throw new Error('Error 1'); },
        () => { throw new TypeError('Error 2'); },
        () => { throw new ReferenceError('Error 3'); }
    ];
    
    const results = scenarios.map(scenario => {
        try {
            scenario();
            return { passed: false };
        } catch (error) {
            return { passed: true, error: error.name };
        }
    });
    
    return results;
}

Output

Error test: true

Understanding Error Testing

Error testing ensures proper handling.

Error Throwing Tests

•Verify errors thrown

•Check error messages

•Validate error types

Error Type Tests

•instanceof checks

•Error names

•Custom error types

Mock Scenarios

•Network errors

•Timeout errors

•Validation errors

•Various failures

Assertion Helpers

•Check error thrown

•Verify error type

•Test error handling

Async Error Tests

•Promise rejections

•Async/await errors

•Error propagation

Integration Tests

•Multiple scenarios

•Error boundaries

•Recovery logic

Best Practices

•Test all error paths

•Mock error scenarios

•Verify error handling

•Test recovery

Let us now understand every line and the components of the above program.

Note: To write and run JavaScript programs, you need to set up the local environment on your computer. Refer to the complete article Setting up JavaScript Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your JavaScript programs.

Practical Learning Notes for Error Testing

This JavaScript program is part of the "Error Handling" topic and is designed to help you build real problem-solving confidence, not just memorize syntax. Start by understanding the goal of the program in plain language, then trace the logic line by line with a custom input of your own. Once you can predict the output before running the code, your understanding becomes much stronger.

A reliable practice pattern is to run the original version first, then modify only one condition or variable at a time. Observe how that single change affects control flow and output. This deliberate style helps you understand loops, conditions, and data movement much faster than copying full solutions repeatedly.

For interview preparation, explain this solution in three layers: the high-level approach, the step-by-step execution, and the time-space tradeoff. If you can teach these three layers clearly, you are ready to solve close variations of this problem under time pressure.

Error Recovery