add create_client tests

test/helpers/create_client.js

@@ -0,0 +1,28 @@
+import expect from 'expect.js';
+import proxyquire from 'proxyquire';
+
+const elasticsearchMock = {
+  Client: function Client() {}
+};
+
+const createClient = proxyquire.noPreserveCache()('../../lib/helpers/create_client', {
+  elasticsearch: elasticsearchMock
+});
+
+describe('Create client helper', function () {
+  it('should have a client', function () {
+    const options = {
+      host: 'http://localhost:9200'
+    };
+    const client = createClient(options);
+
+    expect(client).to.be.a(elasticsearchMock.Client);
+  });
+
+  it('should use passed in instance', function () {
+    const clientInstance = new elasticsearchMock.Client();
+    const client = createClient(clientInstance);
+
+    expect(client).to.equal(clientInstance);
+  });
+});