Added validation of provided LoggerProvider

lib/logger.js

@@ -9,7 +9,17 @@ module.exports = exports = function getLogger(name) {
 };
 
 exports.setLoggerProvider = function setLoggerProvider(provider) {
+    validate(typeof provider == 'function', 'Provider needs to be a function');
+
+    const logger = provider('unleash:logger');
+
+    validate(typeof logger.debug == 'function', 'Logger must implement debug');
+    validate(typeof logger.info == 'function', 'Logger must implement info');
+    validate(typeof logger.warn == 'function', 'Logger must implement warn');
+    validate(typeof logger.error == 'function', 'Logger must implement error');
+
     loggerProvider = provider;
+    logger.info('Custom Logger Provider initalized.');
 };
 
 function getDefaultLogProvider() {
@@ -31,3 +41,9 @@ function getDefaultLogProvider() {
 
     return log4js.getLogger;
 }
+
+function validate(isValid, msg) {
+    if (!isValid) {
+        throw new TypeError(msg);
+    }
+}

lib/logger.test.js

@@ -3,20 +3,49 @@
 const { test } = require('ava');
 const createLogger = require('./logger');
 const logger = require('../logger');
-const sinon = require('sinon');
 
 test('should expose a setLoggerProvider function', t => {
     t.true(logger.setLoggerProvider instanceof Function);
 });
 
 test('should create logger via custom logger provider', t => {
-    const provider = sinon.stub();
     const loggerName = 'test';
-    const loggerImpl = {};
-    provider.withArgs(loggerName).returns(loggerImpl);
+    const loggerImpl = {
+        debug: () => {},
+        info: () => {},
+        warn: () => {},
+        error: () => {},
+    };
+    const provider = () => loggerImpl;
     logger.setLoggerProvider(provider);
 
     const log = createLogger(loggerName);
 
     t.is(log, loggerImpl);
 });
+
+test('should require custom logger to implement info', t => {
+    const loggerImpl = {
+        debug: () => {},
+        warn: () => {},
+        error: () => {},
+    };
+    const provider = () => loggerImpl;
+    const error = t.throws(() => {
+        logger.setLoggerProvider(provider)();
+    }, TypeError);
+    t.is(error.message, 'Logger must implement info');
+});
+
+test('should require custom logger to implement error', t => {
+    const loggerImpl = {
+        debug: () => {},
+        warn: () => {},
+        info: () => {},
+    };
+    const provider = () => loggerImpl;
+    const error = t.throws(() => {
+        logger.setLoggerProvider(provider)();
+    }, TypeError);
+    t.is(error.message, 'Logger must implement error');
+});