assert

This module is used for writing unit tests for your applications, you can access it with require('assert').

The API is derived from the commonjs 1.0 unit testing spec and the node.js assert module

assert.fail(actual, expected, message, operator)

Throws an exception that displays the values for actual and expected separated by the provided operator.

assert(value, message), assert.ok(value, [message])

Tests if value is truthy, it is equivalent to assert.equal(true, !!value, message);

assert.equal(actual, expected, [message])

Tests shallow, coercive equality with the equal comparison operator ( == ).

assert.notEqual(actual, expected, [message])

Tests shallow, coercive non-equality with the not equal comparison operator ( != ).

assert.deepEqual(actual, expected, [message])

Tests for deep equality.

assert.deepStrictEqual(actual, expected, [message])

Tests for deep equality, as determined by the strict equality operator ( === )

assert.notDeepEqual(actual, expected, [message])

Tests for any deep inequality.

assert.strictEqual(actual, expected, [message])

Tests strict equality, as determined by the strict equality operator ( === )

assert.notStrictEqual(actual, expected, [message])

Tests strict non-equality, as determined by the strict not equal operator ( !== )

assert.throws(block, [error], [message])

Expects block to throw an error. error can be constructor, regexp or validation function.

Validate instanceof using constructor:

assert.throws(function() { throw new Error("Wrong value"); }, Error);

Validate error message using RegExp:

assert.throws(function() { throw new Error("Wrong value"); }, /value/);

Custom error validation:

assert.throws(function() {
    throw new Error("Wrong value");
}, function(err) {
    if ( (err instanceof Error) && /value/.test(err) ) {
        return true;
    }
}, "unexpected error");

assert.doesNotThrow(block, [message])

Expects block not to throw an error, see assert.throws for details.

assert.ifError(value)

Tests if value is not a false value, throws if it is a true value. Useful when testing the first argument, error in callbacks.