Assert module for assertions in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this assertion code?

Consider the following Node.js code using the assert module. What happens when it runs?

Node.js

import assert from 'assert';

const value = 5;
assert.strictEqual(value, 5);
console.log('Assertion passed');

A Logs nothing and silently fails.

B Throws an AssertionError because values are not strictly equal.

C Throws a ReferenceError because assert is not imported correctly.

D Logs 'Assertion passed' to the console without errors.

💡 Hint

Check if the values compared by assert.strictEqual are exactly the same.

assert.strictEqual checks if the two values are strictly equal (===). Since value is 5 and compared to 5, the assertion passes and the console.log runs.

❓ Predict Output

intermediate

What error does this assertion code raise?

Look at this Node.js code snippet using the assert module. What error will it throw?

Node.js

import assert from 'assert';

const obj1 = { a: 1 };
const obj2 = { a: 1 };
assert.strictEqual(obj1, obj2);

A Throws AssertionError because obj1 and obj2 are different objects.

B No error, assertion passes because objects have same properties.

C Throws TypeError because objects cannot be compared.

D Throws ReferenceError because assert is not defined.

💡 Hint

Remember that strictEqual compares object references, not their content.

assert.strictEqual compares if both operands refer to the exact same object. obj1 and obj2 are different objects with same content, so assertion fails.

❓ component_behavior

advanced

What happens when assert.throws is used incorrectly?

Given this code using assert.throws, what is the behavior?

Node.js

import assert from 'assert';

function testFunc() {
  return 42;
}

assert.throws(() => testFunc(), Error);

A Throws an AssertionError because testFunc does not throw an error.

B Throws no error and logs 'Test passed'.

C Throws a TypeError because assert.throws expects a promise.

D Passes silently because testFunc returns a value.

💡 Hint

assert.throws expects the function to throw an error to pass.

assert.throws checks if the function throws an error. Since testFunc returns a value and does not throw, assert.throws fails and throws an AssertionError.

📝 Syntax

advanced

Which option correctly uses assert.deepStrictEqual?

Which code snippet correctly asserts that two objects with nested properties are deeply equal?

A assert.strictEqual({a: {b: 1}}, {a: {b: 1}});

B assert.deepStrictEqual({a: {b: 1}}, {a: {b: 1}});

C assert.deepEqual({a: {b: 1}}, {a: {b: 1}});

D assert.equal({a: {b: 1}}, {a: {b: 1}});

💡 Hint

Use deepStrictEqual to compare nested objects for exact equality.

assert.deepStrictEqual compares nested objects recursively and checks for strict equality of values. Other methods either do shallow comparison or are deprecated.

🔧 Debug

expert

Why does this assertion code fail unexpectedly?

Examine this code snippet. Why does the assertion fail even though the objects look identical?

Node.js

import assert from 'assert';

const arr1 = [1, 2, 3];
const arr2 = [1, 2, '3'];
assert.deepStrictEqual(arr1, arr2);

A Passes because values are loosely equal.

B Fails because arrays cannot be compared with deepStrictEqual.

C Fails because the third element in arr2 is a string, not a number.

D Fails because assert.deepStrictEqual is deprecated.

💡 Hint

Check the data types of each element in the arrays.

assert.deepStrictEqual checks both value and type. The third element in arr1 is number 3, but in arr2 it is string '3', causing the assertion to fail.