diff --git a/spec/controllers/mushrooms_controller_spec.rb b/spec/controllers/mushrooms_controller_spec.rb
new file mode 100644
index 0000000..82864a2
--- /dev/null
+++ b/spec/controllers/mushrooms_controller_spec.rb
@@ -0,0 +1,28 @@
+require 'rails_helper'
+
+RSpec.describe MushroomsController, type: :controller do
+  describe '#index' do
+    context 'when filter params is present' do
+      it 'runs the FilterMushroom service and returns results' do
+        get :index, params: { filter: { odor: 'almond' } }
+
+        allow(FilterMushroom.new(response.request.params[:filter], 1))
+          .to receive(:run)
+
+        expect(response).to have_http_status(200)
+        expect(response).to render_template(:index)
+      end
+    end
+
+    context 'when filter params is NOT present' do
+      it 'renders the index template' do
+        get :index
+
+        expect(FilterMushroom).not_to receive(:new)
+
+        expect(response).to have_http_status(200)
+        expect(response).to render_template(:index)
+      end
+    end
+  end
+end