Yaaay, we have a working test

app/controllers/metrics_controller.rb

@@ -21,8 +21,13 @@ def set_data
   end
 
   def set_dates
-    @first_metric_date = current_user.oldest_metric_date
-    @latest_metric_date = current_user.newest_metric_date
+    if current_user.metrics.any?
+      @first_metric_date = current_user.oldest_metric_date
+      @latest_metric_date = current_user.newest_metric_date
+    else
+      @first_metric_date = Date.today
+      @latest_metric_date = Date.today
+    end
   end
 
   def set_app_titles

config/environments/test.rb

@@ -36,4 +36,5 @@
 
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
+  config.active_support.test_order = :random
 end

test/controllers/home_controller_test.rb

@@ -1,7 +1,5 @@
 require "test_helper"
 
 class HomeControllerTest < ActionController::TestCase
-  # test "the truth" do
-  #   assert true
-  # end
+
 end

test/controllers/metrics_controller_test.rb

@@ -1,7 +1,10 @@
 require "test_helper"
 
 class MetricsControllerTest < ActionController::TestCase
-  # test "the truth" do
-  #   assert true
-  # end
+  test "should get index" do
+    sign_in users(:regular)
+
+    get :index
+    assert_response :success
+  end
 end

test/fixtures/users.yml

@@ -4,8 +4,6 @@
 # model remove the '{}' from the fixture names and add the columns immediately
 # below each fixture, per the syntax in the comments below
 #
-one: {}
-# column: value
-#
-two: {}
-#  column: value
+regular:
+  email: [email protected]
+  encrypted_password: <%= User.new.send(:password_digest, '123greetings') %>

test/support/rails_4_thread_error_fix.rb

@@ -0,0 +1,14 @@
+if RUBY_VERSION>='2.6.0'
+  if Rails.version < '5'
+    class ActionController::TestResponse < ActionDispatch::TestResponse
+      def recycle!
+        # hack to avoid MonitorMixin double-initialize error:
+        @mon_mutex_owner_object_id = nil
+        @mon_mutex = nil
+        initialize
+      end
+    end
+  else
+    puts "Monkeypatch for ActionController::TestResponse no longer needed"
+  end
+end

test/test_helper.rb

@@ -2,6 +2,9 @@
 require File.expand_path("../../config/environment", __FILE__)
 require "rails/test_help"
 
+# TODO: Remove this when Rails 4 is no longer supported.
+require_relative "./support/rails_4_thread_error_fix"
+
 class ActiveSupport::TestCase
   # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
   #
@@ -10,4 +13,9 @@ class ActiveSupport::TestCase
   fixtures :all
 
   # Add more helper methods to be used by all tests here...
+
+end
+
+class ActionController::TestCase
+  include Devise::TestHelpers
 end