test backbeat config validation

Issue: BB-623

lib/Config.js

@@ -55,6 +55,15 @@ class Config extends EventEmitter {
             throw new Error(`could not parse config file: ${err.message}`);
         }
 
+        this._parseConfig(config);
+    }
+
+    /**
+     * Parses Backbeat's configuration
+     * @param {Object} config backbeat configuration
+     * @returns {undefined}
+     */
+    _parseConfig(config) {
         const parsedConfig = joi.attempt(config, backbeatConfigJoi);
 
         if (parsedConfig.extensions) {

tests/unit/lib/config/Config.spec.js

@@ -0,0 +1,25 @@
+'use strict'; // eslint-disable-line
+
+const assert = require('assert');
+
+const { Config } = require('../../../../lib/Config');
+const backbeatConfig = require('./config.json');
+
+describe('Config', () => {
+    it('should make the probeserver config in the queuePoulator' +
+        'required when multiple extensions are configured', () => {
+        const config = new Config();
+        const testConfig = { ...backbeatConfig };
+        delete testConfig.queuePopulator.probeServer;
+        assert.throws(() => config._parseConfig(testConfig));
+    });
+
+    it('should make the probeserver config in the queuePoulator' +
+        'optional when only notification config is specified', () => {
+        const config = new Config();
+        const testConfig = { ...backbeatConfig };
+        delete testConfig.queuePopulator.probeServer;
+        testConfig.extensions = { notification: testConfig.extensions.notification };
+        assert.doesNotThrow(() => config._parseConfig(testConfig));
+    });
+});