[AnalyzerSpec] Fix spec for lockfile checkout options

Make it more like an environment where the source is already downloaded.

spec/unit/installer/analyzer_spec.rb

@@ -633,6 +633,10 @@ module Pod
       before do
         @sandbox_manifest = Pod::Lockfile.new(@lockfile.internal_data.deep_dup)
         @analyzer.sandbox.manifest = @sandbox_manifest
+        @analyzer.sandbox.stubs(:specification).with('BananaLib').returns(stub)
+        pod_dir = stub
+        pod_dir.stubs(:directory?).returns(true)
+        @analyzer.sandbox.stubs(:pod_dir).with('BananaLib').returns(pod_dir)
       end
 
       it 'returns whether or not an update is required' do