Add specs for AWS vs. unsigned elasticsearch clients

lib/gitlab/elastic/client.rb

+# This file is required by `bin/elastic_repo_indexer` as well as from within
+# Rails, so needs to explicitly require its dependencies
 require 'elasticsearch'
 require 'aws-sdk'
 require 'faraday_middleware/aws_signers_v4'

spec/lib/gitlab/elastic/client_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Elastic::Client do
+  describe 'build' do
+    let(:client) { described_class.build(params) }
+
+    context 'without credentials' do
+      let(:params) { { url: 'http://dummy-elastic:9200' } }
+
+      it 'makes unsigned requests' do
+        stub_request(:get, 'http://dummy-elastic:9200/foo/_all/1')
+          .with(headers: { 'Content-Type' => 'application/json' })
+          .to_return(status: 200, body: [:fake_response])
+
+        expect(client.get(index: 'foo', id: 1)).to eq([:fake_response])
+      end
+    end
+
+    context 'with AWS IAM credentials' do
+      let(:params) do
+        {
+          url: 'http://example-elastic:9200',
+          aws: true,
+          aws_region: 'us-east-1',
+          aws_access_key: '0',
+          aws_secret_access_key: '0',
+        }
+      end
+
+      it 'signs requests' do
+        travel_to(Time.parse('20170303T133952Z')) do
+          stub_request(:get, 'http://example-elastic:9200/foo/_all/1')
+            .with(
+              headers: {
+               'Authorization'        => 'AWS4-HMAC-SHA256 Credential=0/20170303/us-east-1/es/aws4_request, SignedHeaders=content-type;host;x-amz-content-sha256;x-amz-date, Signature=4ba2aae19a476152dacf5a2191da67b0cf81b9d7152dab5c42b1bba701da19f1',
+               'Content-Type'         => 'application/json',
+               'X-Amz-Content-Sha256' => 'e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855',
+               'X-Amz-Date'           => '20170303T133952Z',
+            })
+            .to_return(status: 200, body: [:fake_response])
+
+          expect(client.get(index: 'foo', id: 1)).to eq([:fake_response])
+        end
+      end
+    end
+  end
+end