ensure that webpacker is not used when shakapacker in use in tests

Author: AbanoubGhadban

spec/react_on_rails/utils_spec.rb

@@ -32,6 +32,7 @@ module ReactOnRails
 
       # We don't need to mock anything here because the shakapacker gem is already installed and will be used by default
       it "uses shakapacker" do
+        expect(ReactOnRails::PackerUtils.using_webpacker_const?).to be(false)
         expect(ReactOnRails::PackerUtils.using_shakapacker_const?).to be(true)
         expect(ReactOnRails::PackerUtils.packer_type).to eq("shakapacker")
         expect(ReactOnRails::PackerUtils.packer).to eq(::Shakapacker)