ExpectationError

Defined in: packages/engine/src/testing/index.ts:63

The failure a matcher throws when an expectation is not met.

A dedicated Error subclass rather than a bare throw new Error, so a caller (or a reporter) can tell a kit assertion failure apart from an unrelated exception with instanceof, and so the structured expected and actual fields survive alongside the human-readable message. This is NOT an EngineError: that type classifies pipeline-stage failures inside the engine, whereas this classifies a test-assertion mismatch, a different concern that would be miscategorised under any of EngineError’s categories.

Extends

• Error

Constructors

Constructor

new ExpectationError(init): ExpectationError;

Defined in: packages/engine/src/testing/index.ts:71

Parameters

Parameter	Type
init	{ actual?: string; code: string; expected?: string; message: string; }
init.actual?	string
init.code	string
init.expected?	string
init.message	string

Returns

ExpectationError

Overrides

Error.constructor

Properties

actual?

readonly optional actual?: string;

Defined in: packages/engine/src/testing/index.ts:69

What it found instead.

---

code

readonly code: string;

Defined in: packages/engine/src/testing/index.ts:65

A short, machine-readable label for which expectation failed.

---

expected?

readonly optional expected?: string;

Defined in: packages/engine/src/testing/index.ts:67

What the matcher was told to expect, in plain words.

---

message

message: string;

Defined in: docs/node_modules/typescript/lib/lib.es5.d.ts:1075

Inherited from

Error.message

---

name

name: string;

Defined in: docs/node_modules/typescript/lib/lib.es5.d.ts:1074

Inherited from

Error.name

---

stack?

optional stack?: string;

Defined in: docs/node_modules/typescript/lib/lib.es5.d.ts:1076

Inherited from

Error.stack

---

stackTraceLimit

static stackTraceLimit: number;

Defined in: node_modules/@types/node/globals.d.ts:67

The Error.stackTraceLimit property specifies the number of stack frames collected by a stack trace (whether generated by new Error().stack or Error.captureStackTrace(obj)).

The default value is 10 but may be set to any valid JavaScript number. Changes will affect any stack trace captured after the value has been changed.

If set to a non-number value, or set to a negative number, stack traces will not capture any frames.

Inherited from

Error.stackTraceLimit

Methods

captureStackTrace()

static captureStackTrace(targetObject, constructorOpt?): void;

Defined in: node_modules/@types/node/globals.d.ts:51

Creates a .stack property on targetObject, which when accessed returns a string representing the location in the code at which Error.captureStackTrace() was called.

const myObject = {};
Error.captureStackTrace(myObject);
myObject.stack;  // Similar to `new Error().stack`

The first line of the trace will be prefixed with ${myObject.name}: ${myObject.message}.

The optional constructorOpt argument accepts a function. If given, all frames above constructorOpt, including constructorOpt, will be omitted from the generated stack trace.

The constructorOpt argument is useful for hiding implementation details of error generation from the user. For instance:

function a() {
  b();
}

function b() {
  c();
}

function c() {
  // Create an error without stack trace to avoid calculating the stack trace twice.
  const { stackTraceLimit } = Error;
  Error.stackTraceLimit = 0;
  const error = new Error();
  Error.stackTraceLimit = stackTraceLimit;

  // Capture the stack trace above function b
  Error.captureStackTrace(error, b); // Neither function c, nor b is included in the stack trace
  throw error;
}

a();

Parameters

Parameter	Type
targetObject	object
constructorOpt?	Function

Returns

void

Inherited from

Error.captureStackTrace

---

prepareStackTrace()

static prepareStackTrace(err, stackTraces): any;

Defined in: node_modules/@types/node/globals.d.ts:55

Parameters

Parameter	Type
err	Error
stackTraces	CallSite[]

Returns

any

See

https://v8.dev/docs/stack-trace-api#customizing-stack-traces

Inherited from

Error.prepareStackTrace