index.test.js

const middy = require('@middy/core');
const createError = require('http-errors');
const middleware = require('./index');

const error = new createError.NotFound('File not found');

test('Middleware works with logging disabled', async () => {
    const handler = middy(() => {
        throw error;
    });

    handler.use(middleware({ logger: false }));

    await expect(handler({}, {})).resolves.toMatchObject({
        body: JSON.stringify({ statusCode: 404, message: 'File not found' }),
        statusCode: 404,
    });
});

test("Middleware doesn't log 404 errors - they happen a lot", async () => {
    const mockLogger = {
        error: jest.fn(() => {}),
    };

    const handler = middy(() => {
        throw new createError.NotFound('File not found');
    });

    handler.use(middleware({ logger: mockLogger, filter: (err) => err.statusCode >= 500 }));

    const response = await handler({}, {});
    const { statusCode, message, stack } = JSON.parse(response.body);

    expect(statusCode).toBe(404);
    expect(message).toBe('File not found');
    expect(stack).toBeUndefined();

    expect(mockLogger.error).toHaveBeenCalledTimes(0);
});

test('Middleware logs and returns all error details', async () => {
    const mockLogger = {
        error: jest.fn(() => {}),
    };

    const handler = middy(() => {
        throw new createError.ServiceUnavailable('Service not available');
    });

    handler.use(middleware({ logger: mockLogger, exposeStackTrace: true }));

    const response = await handler({}, {});
    const { statusCode, message, stack } = JSON.parse(response.body);

    expect(statusCode).toBe(503);
    expect(message).toBe('Service not available');
    expect(stack).toBeDefined();

    expect(mockLogger.error).toHaveBeenCalledTimes(1);

    const [errorObject, errorMessage] = mockLogger.error.mock.calls[mockLogger.error.mock.calls.length - 1];
    expect(errorMessage).toBe('ServiceUnavailableError: Service not available');
    expect(errorObject.error.name).toBe('ServiceUnavailableError');
    expect(errorObject.error.message).toBe('Service not available');
    expect(errorObject.error.status).toBe(503);
    expect(errorObject.error.statusCode).toBe(503);
    expect(errorObject.error.expose).toBe(false);
    expect(errorObject.error.stack).not.toBeNull();
});

test('Keep data already present in response', async () => {
    const handler = middy(async () => {
        throw error;
    });

    handler.use(middleware({ logger: false }));

    // eslint-disable-next-line no-shadow
    handler.onError(async (handler) => {
        // eslint-disable-next-line no-param-reassign
        handler.response = {
            headers: {
                someHeader: 'someValue',
            },
        };
    });

    await expect(handler({}, {})).resolves.toMatchObject({
        body: JSON.stringify({ statusCode: 404, message: 'File not found' }),
        statusCode: 404,
        headers: { someHeader: 'someValue' },
    });
});