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assert.AssertionError

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class assert.AssertionError extends errors.Error

Indicates the failure of an assertion. All errors thrown by the node:assert module will be instances of the AssertionError class.

C

assert.AssertionError Constructor

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new assert.AssertionError(options): assert.AssertionError
Attributes
options:Object
message:string
If provided, the error message is set to this value.
actual:any
The actual property on the error instance.
expected:any
The expected property on the error instance.
operator:string
The operator property on the error instance.
stackStartFn:Function
If provided, the generated stack trace omits frames before this function.
diff:string
If set to 'full', shows the full diff in assertion errors. Defaults to 'simple'. Accepted values: 'simple', 'full'.

A subclass of Error that indicates the failure of an assertion.

All instances contain the built-in Error properties (message and name) and:

Attributes
actual:any
Set to the actual argument for methods such as assert.strictEqual().
expected:any
Set to the expected value for methods such as assert.strictEqual().
generatedMessage:boolean
Indicates if the message was auto-generated (true) or not.
code:string
Value is always ERR_ASSERTION to show that the error is an assertion error.
operator:string
Set to the passed in operator value.
import assert from 'node:assert';

// Generate an AssertionError to compare the error message later:
const { message } = new assert.AssertionError({
  actual: 1,
  expected: 2,
  operator: 'strictEqual',
});

// Verify error output:
try {
  assert.strictEqual(1, 2);
} catch (err) {
  assert(err instanceof assert.AssertionError);
  assert.strictEqual(err.message, message);
  assert.strictEqual(err.name, 'AssertionError');
  assert.strictEqual(err.actual, 1);
  assert.strictEqual(err.expected, 2);
  assert.strictEqual(err.code, 'ERR_ASSERTION');
  assert.strictEqual(err.operator, 'strictEqual');
  assert.strictEqual(err.generatedMessage, true);
}
JavaScript
const assert = require('node:assert');

// Generate an AssertionError to compare the error message later:
const { message } = new assert.AssertionError({
  actual: 1,
  expected: 2,
  operator: 'strictEqual',
});

// Verify error output:
try {
  assert.strictEqual(1, 2);
} catch (err) {
  assert(err instanceof assert.AssertionError);
  assert.strictEqual(err.message, message);
  assert.strictEqual(err.name, 'AssertionError');
  assert.strictEqual(err.actual, 1);
  assert.strictEqual(err.expected, 2);
  assert.strictEqual(err.code, 'ERR_ASSERTION');
  assert.strictEqual(err.operator, 'strictEqual');
  assert.strictEqual(err.generatedMessage, true);
}
JavaScript
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