> For the complete documentation index, see [llms.txt](https://ploegert.gitbook.io/til/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ploegert.gitbook.io/til/programmy/rails/test-if-an-instance-variable-was-assigned.md).

# Test If An Instance Variable Was Assigned

When testing Rails controller actions, you'll often be making assertions about the response to your test request. You may also want to assert about the instance variables being set, as those are headed for your view layer.

For instance, if an instance variable `@metadata` is supposed to be set in a `#show` controller action, you can assert that it is with [RSpec's `assigns`](https://relishapp.com/rspec/rspec-rails/docs/controller-specs):

```ruby
describe "when given valid params" do
  it "sets the metadata" do
    get :show, params: valid_params

    expect(assigns(:metadata)).to match(
      identifier: "abc123",
      session_id: "fe98f08c-bf2f-4749-9f81-071d9cc7720e",
    )
  end
end
```

[source](https://stackoverflow.com/questions/2051373/how-to-test-instance-variable-was-instantiated-in-controller-with-rspec)