How to Test Controller with Sign in User on Rails 8 Authentication

Rails 8 ships with built-in authentication, which simplifies login flows without requiring third-party gems like Devise. But with any new convention, there’s a learning curve—especially when writing tests.

If you’re writing controller tests with Minitest and running into issues after enabling authentication, you’re not alone. Here’s what you might see:

Problem: Unexpected Redirect to Login

You might get a test failure like this:

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Failure:
TicketsControllerTest#test_should_get_index:
Expected response to be a <2XX: success>, but was a <302: Found> redirect to <http://www.example.com/session/new>

The Mistake

A common pitfall is using the wrong route for signing in. In Rails 8’s built-in auth, the route for signing in is:

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POST /session
But many developers mistakenly use new_session_url, which is a GET request for the login form, not the login action.

The Fix: Use the Correct Route and Parameters

Update your test helper or controller test to use the proper login route like this:

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def sign_in(user)
  post session_url, params: { email_address: user.email_address, password: "password" }
end

Make sure this sign_in method is called before making authenticated requests in your tests.

Example Controller Test (Minitest)

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require "test_helper"
class TicketsControllerTest < ActionDispatch::IntegrationTest
  setup do
    @user = users(:one)
    sign_in(@user)
  end

  test "should get index" do
    get tickets_url
    assert_response :success
  end
  private
  def sign_in(user)
    post session_url, params: {
      email_address: user.email_address,
      password: "password"
    }
  end
end

Also Read:

Design Patterns in Rails