Add forgotten unit test

The test should have been added as part of #859

[Back-port pull request #862]

test/datasource.test.js

@@ -0,0 +1,21 @@
+var should = require('./init.js');
+var DataSource = require('../lib/datasource.js').DataSource;
+
+describe('DataSource', function() {
+  it('reports helpful error when connector init throws', function() {
+    var throwingConnector = {
+      name: 'loopback-connector-throwing',
+      initialize: function(ds, cb) {
+        throw new Error('expected test error');
+      },
+    };
+
+    (function() {
+      // this is what LoopBack does
+      return new DataSource({
+        name: 'dsname',
+        connector: throwingConnector
+      });
+    }).should.throw(/loopback-connector-throwing/);
+  });
+});