ErrorResultGuard

@vendure/testing Source

A utility class which is used to assert the success of an operation which returns a union type of SuccessType | ErrorResponse [ | ErrorResponse ]. The methods of this class are used to:

assert that the result is a success or error case
narrow the type so that TypeScript can correctly infer the properties of the result.

Example

const orderResultGuard: ErrorResultGuard<AddItemToOrderResult>  = createErrorResultGuard(order => !!order.lines);it('errors when quantity is negative', async () => {   const { addItemToOrder } = await shopClient.query<AddItemToOrder.Query, AddItemToOrder.Mutation>(ADD_ITEM_TO_ORDER, {     productVariantId: 42, quantity: -1,   });   // The test will fail   orderResultGuard.assertErrorResult(addItemToOrder);   // the type of `addItemToOrder` has now been   // narrowed to only include the ErrorResult types.   expect(addItemToOrder.errorCode).toBe(ErrorCode.NegativeQuantityError);}

Signature

class ErrorResultGuard<T> {    constructor(testFn: (input: T) => boolean)    isSuccess(input: T | any) => input is T;    assertSuccess(input: T | R) => asserts input is T;    assertErrorResult(input: T | R) => asserts input is R;}

constructor

method(testFn: (input: T) => boolean) => ErrorResultGuard

isSuccess

method(input: T | any) => input is T

A type guard which returns true if the input passes the testFn predicate.

assertSuccess

method(input: T | R) => asserts input is T

Asserts (using the testing library's fail() function) that the input is successful, i.e. it passes the testFn.

assertErrorResult

method(input: T | R) => asserts input is R

Asserts (using the testing library's fail() function) that the input is not successful, i.e. it does not pass the testFn.