Redirect to home if remove yourself from the collection

app/controllers/collections_controller.rb

@@ -20,8 +20,11 @@ class CollectionsController < ApplicationController
   def update
     @collection.update! collection_params
     @collection.accesses.revise granted: grantees, revoked: revokees if grantees_changed?
-
-    redirect_to edit_collection_path(@collection), notice: "Saved"
+    if @collection.accessible_to?(Current.user)
+      redirect_to edit_collection_path(@collection), notice: "Saved"
+    else
+      redirect_to root_path, notice: "Saved (you were removed from the collection)"
+    end
   end
 
   def destroy

test/controllers/collections_controller_test.rb

@@ -45,6 +45,18 @@ class CollectionsControllerTest < ActionDispatch::IntegrationTest
     assert_not collections(:writebook).all_access?
   end
 
+  test "update redirects to root when user removes themselves from collection" do
+    collection = collections(:writebook)
+
+    patch collection_path(collection), params: {
+      collection: { name: "Updated name", all_access: false },
+      user_ids: users(:david, :jz).pluck(:id)
+    }
+
+    assert_redirected_to root_path
+    assert_not collection.reload.users.include?(users(:kevin))
+  end
+
   test "update collection with granular permissions, submitting no user ids" do
     assert_not collections(:private).all_access?