diff --git a/app/models/user.rb b/app/models/user.rb
index eeca8e662f..d2692b23dc 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -159,6 +159,6 @@ def requires_name?
   end
 
   def requires_organisation?
-    organisation_id_was.present? || role_changed?(to: :organisation_admin)
+    organisation.blank? && (organisation_id_was.present? || role_changed?(to: :organisation_admin))
   end
 end
diff --git a/spec/factories/models/forms.rb b/spec/factories/models/forms.rb
index 1c467ea0c7..a83ccd3d4c 100644
--- a/spec/factories/models/forms.rb
+++ b/spec/factories/models/forms.rb
@@ -29,11 +29,11 @@
 
     trait :with_group do
       transient do
-        group { nil }
+        group { association :group }
       end
 
       after(:build) do |form, evaluator|
-        g = evaluator.group || FactoryBot.create(:group)
+        g = evaluator.group
         form.instance_variable_set(:@associated_group, g)
         form.define_singleton_method(:group) { g }
       end
@@ -61,7 +61,7 @@
       end
 
       pages do
-        Array.new(pages_count) { association(:page) }
+        Array.new(pages_count) { build(:page, form: nil) }
       end
 
       after(:build) do |form|
@@ -80,7 +80,7 @@
 
     trait :with_text_page do
       pages do
-        Array.new(1) { association(:page, answer_type: "text", answer_settings: { input_type: %w[single_line long_text].sample }) }
+        Array.new(1) { build(:page, answer_type: "text", answer_settings: { input_type: %w[single_line long_text].sample }, form: nil) }
       end
 
       question_section_completed { true }
@@ -148,7 +148,7 @@
       end
 
       pages do
-        Array.new(pages_count) { association(:page, :with_selection_settings) }
+        Array.new(pages_count) { build(:page, :with_selection_settings, form: nil) }
       end
 
       after(:build) do |form|
diff --git a/spec/factories/models/groups.rb b/spec/factories/models/groups.rb
index 6a38ffdbd8..2d88b85735 100644
--- a/spec/factories/models/groups.rb
+++ b/spec/factories/models/groups.rb
@@ -1,13 +1,13 @@
 FactoryBot.define do
   factory :group do
     sequence(:name) { |n| "Group #{n}" }
-    organisation { association :organisation, id: 1, slug: "test-org" }
+    organisation { association :organisation }
     creator { association :user, organisation: }
     status { :trial }
     external_id { SecureRandom.base58(8) }
 
     trait :org_has_org_admin do
-      organisation { association :organisation, :with_org_admin, id: 1, slug: "test-org" }
+      organisation { association :organisation, :with_org_admin }
     end
   end
 end
diff --git a/spec/factories/models/memberships.rb b/spec/factories/models/memberships.rb
index c414e53882..6430f955ca 100644
--- a/spec/factories/models/memberships.rb
+++ b/spec/factories/models/memberships.rb
@@ -1,8 +1,8 @@
 FactoryBot.define do
   factory :membership do
-    user
-    group
-    added_by { association :user }
+    user { build :user }
+    group { build :group, organisation: user&.organisation }
+    added_by { build :user, organisation: user&.organisation }
     role { :editor }
   end
 end
diff --git a/spec/factories/models/mou_signatures.rb b/spec/factories/models/mou_signatures.rb
index 2d3dd13508..a7222cd3d9 100644
--- a/spec/factories/models/mou_signatures.rb
+++ b/spec/factories/models/mou_signatures.rb
@@ -1,13 +1,13 @@
 FactoryBot.define do
   factory :mou_signature do
-    user { create(:user) }
+    user { build(:user) }
     organisation { user.organisation }
     agreement_type { :crown }
     created_at { Time.zone.now }
 
     factory :mou_signature_for_organisation do
       organisation
-      user { create(:user, organisation:) }
+      user { build(:user, organisation:) }
     end
   end
 end
diff --git a/spec/factories/models/organisation_domains.rb b/spec/factories/models/organisation_domains.rb
index 1ac40d7b58..df65d54fcd 100644
--- a/spec/factories/models/organisation_domains.rb
+++ b/spec/factories/models/organisation_domains.rb
@@ -1,6 +1,6 @@
 FactoryBot.define do
   factory :organisation_domain do
-    organisation { association :organisation, id: 1, slug: "test-org" }
+    organisation { association :organisation }
     domain { Faker::Internet.domain_name }
   end
 end
diff --git a/spec/factories/models/organisations.rb b/spec/factories/models/organisations.rb
index edf89a81f8..197d57d5dd 100644
--- a/spec/factories/models/organisations.rb
+++ b/spec/factories/models/organisations.rb
@@ -1,18 +1,14 @@
 FactoryBot.define do
   factory :organisation do
     govuk_content_id { nil }
-    slug { "test-org" }
+    sequence(:slug) { |n| "test-org-#{n}" }
     name { slug.titleize }
     abbreviation { name.split.collect(&:chr).join }
     internal { false }
 
-    initialize_with do
-      Organisation.create_with(govuk_content_id:, name:).find_or_initialize_by(slug:)
-    end
-
     trait :with_signed_mou do
       after(:build) do |organisation|
-        organisation.mou_signatures << (create :mou_signature_for_organisation, organisation:)
+        organisation.mou_signatures << build(:mou_signature_for_organisation, organisation:)
       end
     end
 
@@ -20,7 +16,7 @@
       with_signed_mou
 
       after(:build) do |organisation|
-        organisation.users << create(:organisation_admin_user, organisation:)
+        organisation.users << build(:organisation_admin_user, organisation:)
       end
     end
   end
diff --git a/spec/factories/models/users.rb b/spec/factories/models/users.rb
index 86f5cd40c9..97322ce0fe 100644
--- a/spec/factories/models/users.rb
+++ b/spec/factories/models/users.rb
@@ -26,10 +26,10 @@
       org_has_signed_mou
     end
 
-    organisation { association :organisation, id: 1, slug: "test-org" }
+    organisation { association :organisation }
 
     trait :org_has_signed_mou do
-      organisation { association :organisation, :with_signed_mou, id: 1, slug: "test-org" }
+      organisation { association :organisation, :with_signed_mou }
     end
 
     after(:build) do |user|
diff --git a/spec/features/form/create_or_edit_a_form_spec.rb b/spec/features/form/create_or_edit_a_form_spec.rb
index 900ee6b94e..f826e42720 100644
--- a/spec/features/form/create_or_edit_a_form_spec.rb
+++ b/spec/features/form/create_or_edit_a_form_spec.rb
@@ -2,7 +2,7 @@
 
 feature "Create or edit a form", type: :feature do
   let(:form) { create :form, name: "Apply for a juggling license", created_at: "2024-10-08T07:31:15.762Z" }
-  let(:group) { create :group, name: "Group 1" }
+  let(:group) { create :group, name: "Group 1", organisation: standard_user.organisation }
 
   before do
     login_as_standard_user
diff --git a/spec/features/mou/upgrade_user_changes_mou_spec.rb b/spec/features/mou/upgrade_user_changes_mou_spec.rb
index 5adf9b31b2..1f5ddc3cfb 100644
--- a/spec/features/mou/upgrade_user_changes_mou_spec.rb
+++ b/spec/features/mou/upgrade_user_changes_mou_spec.rb
@@ -3,7 +3,7 @@
 describe "Assign an organisation to a user with a signed MOU", type: :feature do
   let(:user) { create :user, name: "Test User", organisation: nil }
   let!(:mou_signature) { create(:mou_signature, user:, organisation: nil, created_at: Time.zone.parse("September 1, 2023")) }
-  let(:organisation) { create :organisation }
+  let(:organisation) { test_org }
 
   it "a logged in user can sign an MOU" do
     login_as_super_admin_user
diff --git a/spec/input_objects/forms/group_select_spec.rb b/spec/input_objects/forms/group_select_spec.rb
index da28296148..e5dfb70db5 100644
--- a/spec/input_objects/forms/group_select_spec.rb
+++ b/spec/input_objects/forms/group_select_spec.rb
@@ -31,17 +31,12 @@
       end
 
       context "when the organisation admin user is logged in" do
-        let(:org_admin) { build(:organisation_admin_user) }
-
-        it "returns only groups in the user's organisation" do
-          create_list(:group, 3) do |g|
-            g.organisation = group.organisation
-            g.save!
-          end
-          create(:group, organisation: build(:organisation)) # Group 5
+        it "returns only groups in the current group's organisation" do
+          create_list(:group, 3, organisation: group.organisation)
+          create(:group, organisation: build(:organisation)) # Group in a different organisation
 
           expect(group_select.groups).not_to include(group)
-          expect(group_select.groups.count).to eq(4)
+          expect(group_select.groups.count).to eq(3)
         end
       end
 
diff --git a/spec/integration/create_a_form_prevent_double_click_spec.rb b/spec/integration/create_a_form_prevent_double_click_spec.rb
index 46966c13cb..44bf8f7745 100644
--- a/spec/integration/create_a_form_prevent_double_click_spec.rb
+++ b/spec/integration/create_a_form_prevent_double_click_spec.rb
@@ -5,7 +5,7 @@
   let(:unwanted_form) { create :form, name: "Test form", created_at: form.created_at + 0.1 }
 
   let(:group) do
-    group = create :group, name: "Test group", creator: user
+    group = create :group, name: "Test group", creator: user, organisation: user.organisation
     create :membership, group:, user:, added_by: user
     group
   end
diff --git a/spec/integration/organisation_factory_spec.rb b/spec/integration/organisation_factory_spec.rb
index 02ed18bc28..ee7683f2a8 100644
--- a/spec/integration/organisation_factory_spec.rb
+++ b/spec/integration/organisation_factory_spec.rb
@@ -1,13 +1,6 @@
 require "rails_helper"
 
 RSpec.describe "organisation factory" do
-  it "does not duplicate organisations with same slug" do
-    org1 = create :organisation, slug: "org-slug"
-    org2 = create :organisation, slug: "org-slug"
-
-    expect(org1.id).to eq org2.id
-  end
-
   it "does not persist the organisation" do
     org = build :organisation
 
diff --git a/spec/lib/tasks/users.rake_spec.rb b/spec/lib/tasks/users.rake_spec.rb
index aeae16bc25..2b06301618 100644
--- a/spec/lib/tasks/users.rake_spec.rb
+++ b/spec/lib/tasks/users.rake_spec.rb
@@ -142,7 +142,7 @@
       let(:user_in_group) { users.fifth }
 
       before do
-        group = create :group, creator: users.first
+        group = create :group, creator: users.first, organisation: user_in_group.organisation
         create :membership, group:, user: user_in_group, added_by: users.first
       end
 
@@ -181,7 +181,7 @@
       end
 
       let(:user_in_group) { users.fifth }
-      let(:group_with_user) { create :group, creator: users.first }
+      let(:group_with_user) { create :group, creator: users.first, organisation: user_in_group.organisation }
 
       before do
         create :membership, group: group_with_user, user: user_in_group, added_by: users.first
diff --git a/spec/models/group_spec.rb b/spec/models/group_spec.rb
index 707de7e655..95f37228db 100644
--- a/spec/models/group_spec.rb
+++ b/spec/models/group_spec.rb
@@ -126,9 +126,10 @@
 
   describe "associations" do
     it "destroys associated memberships" do
-      group = create :group
-      user = create :user
-      added_by = create :user
+      organisation = create :organisation
+      group = create :group, organisation: organisation
+      user = create :user, organisation: organisation
+      added_by = create :user, organisation: organisation
       create(:membership, group:, user:, added_by:)
 
       expect { group.destroy }.to change(Membership, :count).by(-1)
@@ -151,11 +152,12 @@
     describe "#memberships" do
       describe "#ordered" do
         it "orders the membership records by name of the associated user" do
-          group = create :group
+          organisation = create :organisation
+          group = create :group, organisation: organisation
           users = [
-            create(:user, name: "Barbara User"),
-            create(:user, name: "Alfred User"),
-            create(:user, name: "Charlie User"),
+            create(:user, name: "Barbara User", organisation: organisation),
+            create(:user, name: "Alfred User", organisation: organisation),
+            create(:user, name: "Charlie User", organisation: organisation),
           ]
 
           users.each do |user|
@@ -260,9 +262,10 @@
   describe "scopes" do
     describe ".for_user" do
       it "returns groups that the user is a member of" do
-        user = create :user
-        group1 = create :group
-        group2 = create :group
+        organisation = create :organisation
+        user = create :user, organisation: organisation
+        group1 = create :group, organisation: organisation
+        group2 = create :group, organisation: organisation
         create :group
         create :membership, user:, group: group1
         create :membership, user:, group: group2
@@ -278,8 +281,9 @@
       end
 
       it "does not return groups that the user is not a member of" do
-        user = create :user
-        group1 = create :group
+        organisation = create :organisation
+        user = create :user, organisation: organisation
+        group1 = create :group, organisation: organisation
         create :group
         create :group
         create :membership, user:, group: group1
diff --git a/spec/models/membership_spec.rb b/spec/models/membership_spec.rb
index 8edcf97d6e..e1a6edde97 100644
--- a/spec/models/membership_spec.rb
+++ b/spec/models/membership_spec.rb
@@ -35,16 +35,18 @@
   end
 
   it "is invalid if the user is already a member of the group" do
-    user = create :user
-    group = create :group
+    organisation = create :organisation
+    user = create :user, organisation: organisation
+    group = create :group, organisation: organisation
     create(:membership, user:, group:)
     membership = build(:membership, user:, group:)
     expect(membership).not_to be_valid
   end
 
   it "raises a DB error if the user is already a member of the group" do
-    user = create :user
-    group = create :group
+    organisation = create :organisation
+    user = create :user, organisation: organisation
+    group = create :group, organisation: organisation
     create(:membership, user:, group:)
     membership = build(:membership, user:, group:)
     expect { membership.save(validate: false) }.to raise_error(ActiveRecord::RecordNotUnique)
diff --git a/spec/models/organisation_spec.rb b/spec/models/organisation_spec.rb
index 71b0ee58b7..49854efdd1 100644
--- a/spec/models/organisation_spec.rb
+++ b/spec/models/organisation_spec.rb
@@ -9,19 +9,6 @@
     }.to raise_error ActiveRecord::RecordNotUnique
   end
 
-  describe "factory" do
-    it "does not create organisation if already exists" do
-      existing_organisation = create(:organisation, slug: "duplicate-org")
-      new_organisation = nil
-
-      expect {
-        new_organisation = create(:organisation, slug: "duplicate-org")
-      }.not_to raise_error
-
-      expect(new_organisation).to eq(existing_organisation)
-    end
-  end
-
   describe "versioning", :versioning do
     it "enables paper trail" do
       expect(described_class.new).to be_versioned
diff --git a/spec/models/user_spec.rb b/spec/models/user_spec.rb
index 6a436647d5..5429038ee2 100644
--- a/spec/models/user_spec.rb
+++ b/spec/models/user_spec.rb
@@ -58,6 +58,16 @@
       end
     end
 
+    context "when reassigning to a new, unsaved organisation" do
+      let(:user) { create(:user, organisation: create(:organisation)) }
+
+      it "is valid even though the new organisation is not yet persisted" do
+        user.organisation = build(:organisation)
+
+        expect(user).to be_valid
+      end
+    end
+
     context "when updating name" do
       let(:user) { create :user, :with_no_name }
 
@@ -128,7 +138,7 @@
   describe "associations" do
     it "destroys associated memberships" do
       user = create(:user)
-      group = create(:group)
+      group = create(:group, organisation: user.organisation)
 
       membership = create(:membership, user:, group:)
       user.destroy!
@@ -364,7 +374,7 @@
 
     it "returns false when user had an organisation" do
       user = create(:user)
-      user.update!(organisation: build(:organisation))
+      user.update!(organisation: create(:organisation))
       expect(user).not_to be_given_organisation
     end
   end
@@ -380,9 +390,9 @@
 
     context "when the user is an organisation admin" do
       it "returns true" do
-        user = create(:organisation_admin_user)
+        user = create(:organisation_admin_user, organisation: create(:organisation, :with_signed_mou))
 
-        expect(user.can_administer_org?(organisation)).to be(true)
+        expect(user.can_administer_org?(user.organisation)).to be(true)
       end
     end
 
@@ -414,7 +424,7 @@
       context "and the user's organisation is not the same as given" do
         it "returns false" do
           user = create(:organisation_admin_user)
-          other_org = build(:organisation, id: 2)
+          other_org = build(:organisation)
 
           expect(user.is_organisations_admin?(other_org)).to be(false)
         end
diff --git a/spec/policies/form_policy_spec.rb b/spec/policies/form_policy_spec.rb
index 6227f1c3ef..509a707ae2 100644
--- a/spec/policies/form_policy_spec.rb
+++ b/spec/policies/form_policy_spec.rb
@@ -184,13 +184,13 @@
     end
 
     context "when the user is a super admin" do
-      let(:user) { build :super_admin_user }
+      let(:user) { build :super_admin_user, organisation: }
 
       it { is_expected.to permit_action(:can_administer_group) }
     end
 
     context "when the user is an organisation admin" do
-      let(:user) { build :organisation_admin_user }
+      let(:user) { build :organisation_admin_user, organisation: }
 
       it { is_expected.to permit_action(:can_administer_group) }
     end
diff --git a/spec/requests/api/form_documents_controller_spec.rb b/spec/requests/api/form_documents_controller_spec.rb
index 62109997b3..0711e0fa91 100644
--- a/spec/requests/api/form_documents_controller_spec.rb
+++ b/spec/requests/api/form_documents_controller_spec.rb
@@ -155,12 +155,12 @@
     context "when the form exists" do
       let(:form) { create(:form) }
       let(:group) { create(:group, organisation: test_org) }
-      let(:group_admin) { create(:user) }
+      let(:group_admin) { create(:user, organisation: test_org) }
 
       before do
         organisation_admin_user
         create(:membership, user: group_admin, group:, role: :group_admin)
-        create(:membership, user: create(:user), group:, role: :editor)
+        create(:membership, user: create(:user, organisation: test_org), group:, role: :editor)
 
         group.group_forms.create!(form_id: form.id)
       end
diff --git a/spec/requests/forms/unarchive_controller_spec.rb b/spec/requests/forms/unarchive_controller_spec.rb
index 085a22c7b7..064c880d57 100644
--- a/spec/requests/forms/unarchive_controller_spec.rb
+++ b/spec/requests/forms/unarchive_controller_spec.rb
@@ -27,7 +27,7 @@
     end
 
     context "when current user does not belong to the forms group" do
-      let(:user) { build :user }
+      let(:user) { build :user, organisation: standard_user.organisation }
 
       it "is forbidden" do
         expect(response).to have_http_status(:forbidden)
@@ -119,7 +119,7 @@
     end
 
     context "when current user does not belong to the forms group" do
-      let(:user) { build :user }
+      let(:user) { build :user, organisation: standard_user.organisation }
 
       it "is forbidden" do
         post(unarchive_create_path(form_id: form.id), params: form_params)
diff --git a/spec/requests/groups_controller_spec.rb b/spec/requests/groups_controller_spec.rb
index 1adeb417dd..f638093fce 100644
--- a/spec/requests/groups_controller_spec.rb
+++ b/spec/requests/groups_controller_spec.rb
@@ -66,7 +66,7 @@
       end
     end
 
-    let(:other_org) { create :organisation, id: 2, slug: "other-org" }
+    let(:other_org) { create :organisation, slug: "other-org" }
     let!(:other_org_trial_groups) { create_list :group, 3, organisation: other_org, status: :trial }
 
     context "when the user is not a super-admin" do
@@ -128,7 +128,7 @@
         let!(:other_org_active_groups) { create_list :group, 3, :active, organisation: other_org }
         let!(:other_org_upgrade_requested_groups) { create_list :group, 3, :upgrade_requested, organisation: other_org }
 
-        it "shows groups for organisation in query", :flaky do
+        it "shows groups for organisation in query" do
           get groups_url, params: { search: { organisation_id: other_org.id } }
           expect(assigns(:trial_groups)).to match_array(other_org_trial_groups)
           expect(assigns(:active_groups)).to match_array(other_org_active_groups)
@@ -544,7 +544,7 @@
   end
 
   describe "GET /delete" do
-    let!(:group) { create :group }
+    let!(:group) { create :group, organisation: test_org }
 
     context "when user is a super admin" do
       before do
@@ -598,7 +598,7 @@
   end
 
   describe "DELETE /destroy" do
-    let!(:group) { create :group, name: "Test Group" }
+    let!(:group) { create :group, name: "Test Group", organisation: test_org }
 
     context "when user is a super admin" do
       before do
diff --git a/spec/requests/memberships_controller_spec.rb b/spec/requests/memberships_controller_spec.rb
index 5ef0e95d77..15543c3d90 100644
--- a/spec/requests/memberships_controller_spec.rb
+++ b/spec/requests/memberships_controller_spec.rb
@@ -1,8 +1,8 @@
 require "rails_helper"
 
 describe "/memberships", type: :request do
-  let(:user) { create(:user) }
-  let(:group) { create(:group) }
+  let(:user) { create(:user, organisation: standard_user.organisation) }
+  let(:group) { create(:group, organisation: standard_user.organisation) }
   let(:logged_in_user_role) { :group_admin }
 
   before do
diff --git a/spec/requests/routes_controller_spec.rb b/spec/requests/routes_controller_spec.rb
index 55dd903bd9..5e1c3cb7f8 100644
--- a/spec/requests/routes_controller_spec.rb
+++ b/spec/requests/routes_controller_spec.rb
@@ -3,7 +3,7 @@
 RSpec.describe RoutesController, type: :request do
   let(:form) { create(:form, :with_group, group:) }
   let(:membership) { create :membership, group:, user: standard_user }
-  let(:group) { create(:group, multiple_branches_enabled: true) }
+  let(:group) { create(:group, multiple_branches_enabled: true, organisation: standard_user.organisation) }
 
   before do
     membership
@@ -31,7 +31,7 @@
     end
 
     context "when the multiple_branches feature is not enabled" do
-      let(:group) { create(:group, multiple_branches_enabled: false) }
+      let(:group) { create(:group, multiple_branches_enabled: false, organisation: standard_user.organisation) }
 
       it "returns a 404" do
         get routes_path(form.id)
@@ -89,7 +89,7 @@
     end
 
     context "when the multiple_branches feature is not enabled" do
-      let(:group) { create(:group, multiple_branches_enabled: false) }
+      let(:group) { create(:group, multiple_branches_enabled: false, organisation: standard_user.organisation) }
 
       it "returns a 404" do
         post routes_path(form.id), params: valid_params
diff --git a/spec/services/group_service_spec.rb b/spec/services/group_service_spec.rb
index 510552053b..d142f42b11 100644
--- a/spec/services/group_service_spec.rb
+++ b/spec/services/group_service_spec.rb
@@ -5,16 +5,17 @@
     described_class.new(group:, current_user:, host:)
   end
 
-  let(:group) { create :group }
-  let(:current_user) { create :user }
+  let(:organisation) { create :organisation }
+  let(:group) { create :group, organisation: }
+  let(:current_user) { create :user, organisation: }
   let(:host) { "example.net" }
 
   describe "#upgrade_group" do
-    let(:first_group_admin_user) { create :user }
-    let(:second_group_admin_user) { create :user }
-    let(:editor_user) { create :user }
+    let(:first_group_admin_user) { create :user, organisation: }
+    let(:second_group_admin_user) { create :user, organisation: }
+    let(:editor_user) { create :user, organisation: }
     let(:group) do
-      create(:group).tap do |group|
+      create(:group, organisation:).tap do |group|
         create(:membership, user: first_group_admin_user, group:, role: :group_admin)
         create(:membership, user: second_group_admin_user, group:, role: :group_admin)
         create(:membership, user: editor_user, group:, role: :editor)
@@ -63,11 +64,11 @@
   end
 
   describe "#reject_upgrade" do
-    let(:first_group_admin_user) { create :user }
-    let(:second_group_admin_user) { create :user }
-    let(:editor_user) { create :user }
+    let(:first_group_admin_user) { create :user, organisation: }
+    let(:second_group_admin_user) { create :user, organisation: }
+    let(:editor_user) { create :user, organisation: }
     let(:group) do
-      create(:group, status: :upgrade_requested).tap do |group|
+      create(:group, status: :upgrade_requested, organisation:).tap do |group|
         create(:membership, user: first_group_admin_user, group:, role: :group_admin)
         create(:membership, user: second_group_admin_user, group:, role: :group_admin)
         create(:membership, user: editor_user, group:, role: :editor)
@@ -119,11 +120,12 @@
   end
 
   describe "#request_upgrade" do
-    let!(:first_organisation_admin_user) { create :organisation_admin_user }
-    let!(:second_organisation_admin_user) { create :organisation_admin_user }
-    let(:editor_user) { create :user }
+    let(:organisation) { create :organisation, :with_signed_mou }
+    let!(:first_organisation_admin_user) { create :organisation_admin_user, organisation: }
+    let!(:second_organisation_admin_user) { create :organisation_admin_user, organisation: }
+    let(:editor_user) { create :user, organisation: }
     let(:group) do
-      create(:group).tap do |group|
+      create(:group, organisation:).tap do |group|
         create(:membership, user: editor_user, group:, role: :editor)
         create(:membership, user: current_user, group:, role: :group_admin)
       end
diff --git a/spec/services/mailchimp/list_sync_service_spec.rb b/spec/services/mailchimp/list_sync_service_spec.rb
index 9f2ed1100f..534b11b2c0 100644
--- a/spec/services/mailchimp/list_sync_service_spec.rb
+++ b/spec/services/mailchimp/list_sync_service_spec.rb
@@ -22,8 +22,11 @@
     let(:mou_signer_and_organisation_admin_with_access) { users_with_access.third }
 
     before do
+      signed_mou_org = create(:organisation)
+      signed_mou_org_user = create(:user, organisation: signed_mou_org, has_access: false)
+      create(:mou_signature, organisation: signed_mou_org, user: signed_mou_org_user)
       users_with_access.each do |email|
-        create :user, email:, has_access: true
+        create :user, email:, has_access: true, organisation: signed_mou_org
       end
 
       users_without_access.each do |email|
@@ -69,17 +72,19 @@
   end
 
   describe "#mou_signers" do
-    let(:user_with_access_and_mou) { create(:user, email: "mou_user@example.com") }
-    let(:user_with_access_admin) { create(:user, email: "admin_user@example.com") }
-    let(:user_without_access) { create(:user, email: "inactive_user@example.com", has_access: false) }
-    let(:user_access_and_admin_with_mou) { create(:user, email: "admin_mou_user@example.com") }
-
-    let(:non_crown_org) { create(:organisation, id: 2, slug: "non-crown-org") }
+    let(:signed_mou_org) { create(:organisation) }
+    let(:user_with_access_and_mou) { create(:user, email: "mou_user@example.com", organisation: signed_mou_org) }
+    let(:user_with_access_admin) { create(:user, email: "admin_user@example.com", organisation: signed_mou_org) }
+    let(:user_without_access) { create(:user, email: "inactive_user@example.com", has_access: false, organisation: signed_mou_org) }
+    let(:user_access_and_admin_with_mou) { create(:user, email: "admin_mou_user@example.com", organisation: signed_mou_org) }
+    let(:non_crown_org) { create(:organisation, slug: "non-crown-org") }
     let(:user_that_signed_non_crown_agreement) { create(:user, organisation: non_crown_org) }
     let(:not_org_admin_that_signed_non_crown_agreement) { create(:user, organisation: non_crown_org) }
     let(:org_admin_for_non_crown_org) { create(:user, organisation: non_crown_org) }
+    let!(:signed_mou_org_user) { create(:user, organisation: signed_mou_org, has_access: false) }
 
     before do
+      create(:mou_signature, organisation: signed_mou_org, user: signed_mou_org_user)
       create(:mou_signature, user: user_with_access_and_mou)
       create(:mou_signature, user: user_access_and_admin_with_mou)
       create(:mou_signature, agreement_type: :non_crown, user: user_that_signed_non_crown_agreement)
diff --git a/spec/services/reports/organisations_report_service_spec.rb b/spec/services/reports/organisations_report_service_spec.rb
index 09db119343..1d9af260bc 100644
--- a/spec/services/reports/organisations_report_service_spec.rb
+++ b/spec/services/reports/organisations_report_service_spec.rb
@@ -19,13 +19,12 @@
 
     context "with organisations" do
       it "returns the correct rows" do
-        create(:organisation, name: "Ministry of tests", slug: "ministry-of-tests", organisation_domains: [
-          create(:organisation_domain, domain: "ministry-of-tests.gov.uk"),
-          create(:organisation_domain, domain: "mot.gov.uk"),
-        ])
-        create(:organisation, name: "Department of juggling", slug: "department-of-juggling", organisation_domains: [
-          create(:organisation_domain, domain: "juggling.gov.uk"),
-        ])
+        create(:organisation, name: "Test Org", slug: "test-org")
+        ministry_org = create(:organisation, name: "Ministry of tests", slug: "ministry-of-tests")
+        create(:organisation_domain, domain: "ministry-of-tests.gov.uk", organisation: ministry_org)
+        create(:organisation_domain, domain: "mot.gov.uk", organisation: ministry_org)
+        juggling_org = create(:organisation, name: "Department of juggling", slug: "department-of-juggling")
+        create(:organisation_domain, domain: "juggling.gov.uk", organisation: juggling_org)
 
         expect(service.organisation_domains_report[:rows]).to contain_exactly(
           [{ text: "Test Org" }, { text: "test-org" }, { text: "" }],
diff --git a/spec/support/authentication_feature_helpers.rb b/spec/support/authentication_feature_helpers.rb
index e053985d5f..6d20adcf23 100644
--- a/spec/support/authentication_feature_helpers.rb
+++ b/spec/support/authentication_feature_helpers.rb
@@ -13,7 +13,7 @@ def login_as(user, opts = {})
   end
 
   def test_org
-    @test_org ||= FactoryBot.create(:organisation, :with_signed_mou, id: 1, slug: "test-org")
+    @test_org ||= FactoryBot.create(:organisation, :with_signed_mou, slug: "test-org")
   end
 
   def super_admin_user
diff --git a/spec/views/account/organisations/edit.html.erb_spec.rb b/spec/views/account/organisations/edit.html.erb_spec.rb
index e8e30dccc4..b9e866f79a 100644
--- a/spec/views/account/organisations/edit.html.erb_spec.rb
+++ b/spec/views/account/organisations/edit.html.erb_spec.rb
@@ -65,9 +65,7 @@
 
   context "when there are closed organisations" do
     before do
-      create(:organisation, slug: "test-org")
       create(:organisation, slug: "closed-org", closed: true)
-      create(:organisation, slug: "department-for-testing", name: "Department for Testing")
 
       render
     end
diff --git a/spec/views/groups/index.html.erb_spec.rb b/spec/views/groups/index.html.erb_spec.rb
index adbb1d494f..f336cd5a01 100644
--- a/spec/views/groups/index.html.erb_spec.rb
+++ b/spec/views/groups/index.html.erb_spec.rb
@@ -108,7 +108,7 @@
   end
 
   context "when the user is a super admin" do
-    let(:current_user) { build :super_admin_user }
+    let(:current_user) { create :super_admin_user }
     let(:search_input) { OrganisationSearchInput.new({ organisation_id: current_user.organisation_id }) }
     let(:organisation) { current_user.organisation }
 
diff --git a/spec/views/groups/show.html.erb_spec.rb b/spec/views/groups/show.html.erb_spec.rb
index f9b871b236..adccdf0eb3 100644
--- a/spec/views/groups/show.html.erb_spec.rb
+++ b/spec/views/groups/show.html.erb_spec.rb
@@ -3,7 +3,7 @@
 RSpec.describe "groups/show", type: :view do
   let(:current_user) { create :user, :org_has_signed_mou }
   let(:forms) { [] }
-  let(:group) { create :group, name: "My Group" }
+  let(:group) { create :group, name: "My Group", organisation: current_user.organisation }
 
   let(:form_list_presenter) { FormListPresenter.call(forms:, group:) }
 
@@ -150,7 +150,7 @@
   end
 
   context "when the group is a trial group" do
-    let(:group) { create :group, :trial, name: "trial group" }
+    let(:group) { create :group, :trial, name: "trial group", organisation: current_user.organisation }
 
     it "renders the status of the group" do
       expect(rendered).to have_css ".govuk-caption-l", text: t("groups.status_caption.trial")
@@ -354,7 +354,7 @@
   end
 
   context "when the group has an upgrade requested" do
-    let(:group) { create :group, :upgrade_requested }
+    let(:group) { create :group, :upgrade_requested, organisation: current_user.organisation }
 
     it "have the caption trial group" do
       expect(rendered).to have_css ".govuk-caption-l", text: "Trial group"
@@ -370,7 +370,7 @@
   end
 
   context "when the group is an active group" do
-    let(:group) { create :group, :active, name: "Active group" }
+    let(:group) { create :group, :active, name: "Active group", organisation: current_user.organisation }
 
     it "renders the status of the group" do
       expect(rendered).to have_css ".govuk-caption-l", text: t("groups.status_caption.active")
diff --git a/spec/views/mou_signatures/index.html.erb_spec.rb b/spec/views/mou_signatures/index.html.erb_spec.rb
index 623e036f5f..2fb3750615 100644
--- a/spec/views/mou_signatures/index.html.erb_spec.rb
+++ b/spec/views/mou_signatures/index.html.erb_spec.rb
@@ -3,8 +3,8 @@
 describe "mou_signatures/index.html.erb" do
   let(:mou_signatures) do
     [
-      build(:mou_signature, agreement_type: :crown, created_at: Time.zone.parse("October 12, 2023")),
-      build(:mou_signature, agreement_type: :non_crown, created_at: Time.zone.parse("October 13, 2023")),
+      build(:mou_signature, user: build_stubbed(:user), agreement_type: :crown, created_at: Time.zone.parse("October 12, 2023")),
+      build(:mou_signature, user: build_stubbed(:user), agreement_type: :non_crown, created_at: Time.zone.parse("October 13, 2023")),
     ]
   end