feat: add winston-based logger

test/unit/logging/WinstonLogger.test.ts

@@ -0,0 +1,18 @@
+import { WinstonLogger } from '../../../src/logging/WinstonLogger';
+
+describe('WinstonLogger', (): void => {
+  let innerLogger: any;
+  let logger: WinstonLogger;
+  beforeEach(async(): Promise<void> => {
+    innerLogger = {
+      log: jest.fn(),
+    };
+    logger = new WinstonLogger(innerLogger);
+  });
+
+  it('delegates log invocations to the inner logger.', async(): Promise<void> => {
+    expect(logger.log('debug', 'my message', { abc: true })).toBe(logger);
+    expect(innerLogger.log).toHaveBeenCalledTimes(1);
+    expect(innerLogger.log).toHaveBeenCalledWith('debug', 'my message', { abc: true });
+  });
+});

test/unit/logging/WinstonLoggerFactory.test.ts

@@ -0,0 +1,43 @@
+import { PassThrough } from 'stream';
+import type { Logger } from 'winston';
+import { WinstonLogger } from '../../../src/logging/WinstonLogger';
+import { WinstonLoggerFactory } from '../../../src/logging/WinstonLoggerFactory';
+
+describe('WinstonLoggerFactory', (): void => {
+  let factory: WinstonLoggerFactory;
+  beforeEach(async(): Promise<void> => {
+    factory = new WinstonLoggerFactory('debug');
+  });
+
+  it('creates WinstonLoggers.', async(): Promise<void> => {
+    const logger = factory.createLogger('MyLabel');
+    expect(logger).toBeInstanceOf(WinstonLogger);
+    const innerLogger: Logger = (logger as any).logger;
+    expect(innerLogger.level).toEqual('debug');
+    expect(innerLogger.format).toBeTruthy();
+    expect(innerLogger.transports).toHaveLength(1);
+  });
+
+  it('allows WinstonLoggers to be invoked.', async(): Promise<void> => {
+    // Create a dummy log transport
+    const transport: any = new PassThrough({ objectMode: true });
+    transport.write = jest.fn();
+    transport.log = jest.fn();
+    (factory as any).createTransports = (): any => [ transport ];
+
+    // Create logger, and log
+    const logger = factory.createLogger('MyLabel');
+    logger.log('debug', 'my message');
+
+    expect(transport.write).toHaveBeenCalledTimes(1);
+    expect(transport.write).toHaveBeenCalledWith({
+      label: 'MyLabel',
+      level: expect.stringContaining('debug'),
+      message: 'my message',
+      timestamp: expect.any(String),
+      [Symbol.for('level')]: 'debug',
+      [Symbol.for('splat')]: [ undefined ],
+      [Symbol.for('message')]: expect.any(String),
+    });
+  });
+});