I am testing some express middlewares with jest.
it("should throw 400 error if request.body.id is null", () => {
const req = { body: { id: null } } as any;
const res = {} as any;
const next = jest.fn();
myMiddleware(req, res, next);
expect(next).toBeCalledWith(expect.any(ErrorResponse));
expect(next).toBeCalledWith(
expect.objectContaining({
statusCode: 400,
errCode: "error-0123-2342",
message: "Field id is missing",
})
);
});
my ErrorResponse:
export class ErrorResponse extends Error {
public statusCode: number;
public errCode: string;
constructor(
statusCode: number = 500,
errCode: string = "error-123-1993",
message: string = "Internal Server Error"
) {
super(message);
this.statusCode = statusCode;
this.errCode = errCode;
}
}
I manage to check if the ErrorResponse with specific property is called in the next function, but it doesn't guarantee the ErrorResponse Object contains only 3 properties (statusCode, errCode, message) if someone change the ErrorResponse to add One more property, such as details.
I would like to do something below and guarantee the ErrorResponse Object contains only 3 properties (statusCode, errCode, message).
it("should throw 400 error if request.body.id is null", () => {
const req = { body: { id: null } } as any;
const res = {} as any;
const next = jest.fn();
myMiddleware(req, res, next);
expect(next).toBeCalledWith(
new ErrorResponse(
400,
"error-3123-2332",
"Field id is missing"
)
);
});
May I know if there is an way to do it in jest?
After a cursory look at the jest documentation, it seems that expect.extend might do what you want:
expect.extend({
toBeErrorResponse(received) {
if (received instanceof ErrorResponse &&
Object.keys(received).length === 2)
return {
message: () => "expected no ErrorResponse",
pass: true,
};
else
return {
message: () => "expected an ErrorResponse",
pass: false,
};
}
});
test("my ErrorResponse", () => {
const next = jest.fn();
next(new ErrorResponse(400, "E", "M"));
expect(next).toBeCalledWith(expect.toBeErrorResponse());
});