diff --git a/app/services/waste_carriers_engine/assign_site_details_service.rb b/app/services/waste_carriers_engine/assign_site_details_service.rb
index 5968c32b2..414708b2c 100644
--- a/app/services/waste_carriers_engine/assign_site_details_service.rb
+++ b/app/services/waste_carriers_engine/assign_site_details_service.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module WasteCarriersEngine
   class AssignSiteDetailsService < BaseService
     attr_reader :address
diff --git a/app/services/waste_carriers_engine/determine_area_service.rb b/app/services/waste_carriers_engine/determine_area_service.rb
index 255fe3bef..b8eff1159 100644
--- a/app/services/waste_carriers_engine/determine_area_service.rb
+++ b/app/services/waste_carriers_engine/determine_area_service.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module WasteCarriersEngine
   class DetermineAreaService < BaseService
     def run(easting:, northing:)
diff --git a/app/services/waste_carriers_engine/determine_easting_and_northing_service.rb b/app/services/waste_carriers_engine/determine_easting_and_northing_service.rb
index c15f2602a..d8b4fd395 100644
--- a/app/services/waste_carriers_engine/determine_easting_and_northing_service.rb
+++ b/app/services/waste_carriers_engine/determine_easting_and_northing_service.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 module WasteCarriersEngine
   class DetermineEastingAndNorthingService < BaseService
     def run(postcode:)
diff --git a/spec/services/waste_carriers_engine/assign_site_details_service_spec.rb b/spec/services/waste_carriers_engine/assign_site_details_service_spec.rb
index d36d267c0..727c94ba9 100644
--- a/spec/services/waste_carriers_engine/assign_site_details_service_spec.rb
+++ b/spec/services/waste_carriers_engine/assign_site_details_service_spec.rb
@@ -1,15 +1,15 @@
-require 'rails_helper'
+# frozen_string_literal: true
 
-require 'rails_helper'
+require "rails_helper"
 
 module WasteCarriersEngine
   RSpec.describe AssignSiteDetailsService, type: :service do
-    describe '#run' do
-      let(:x) { 123456 }
-      let(:y) { 654321 }
-      let(:area) { 'Area Name' }
+    describe "#run" do
+      let(:x) { 123_456 }
+      let(:y) { 654_321 }
+      let(:area) { "Area Name" }
 
-      context 'when address has a postcode and area is not present' do
+      context "when address has a postcode and area is not present" do
         let(:address) { build(:address, :has_required_data) }
 
         before do
@@ -17,34 +17,38 @@ module WasteCarriersEngine
           allow(DetermineAreaService).to receive(:run).and_return(area)
         end
 
-        it 'assigns area' do
+        it "assigns area" do
           described_class.run(address: address)
           expect(address.area).to eq(area)
         end
       end
 
-      context 'when address has an area' do
+      context "when address has an area" do
         let(:address) { build(:address, :has_required_data, area: area) }
 
-        it 'does not change the area' do
-          expect(DetermineEastingAndNorthingService).not_to receive(:run)
-          expect(DetermineAreaService).not_to receive(:run)
+        it "does not change the area" do
+          allow(DetermineEastingAndNorthingService).to receive(:run)
+          allow(DetermineAreaService).to receive(:run)
 
           described_class.run(address: address)
 
+          expect(DetermineEastingAndNorthingService).not_to have_received(:run)
+          expect(DetermineAreaService).not_to have_received(:run)
           expect(address.area).to eq(area)
         end
       end
 
-      context 'when address does not have a postcode' do
+      context "when address does not have a postcode" do
         let(:address) { build(:address, :has_required_data, postcode: nil) }
 
-        it 'does not assign area' do
-          expect(DetermineEastingAndNorthingService).not_to receive(:run)
-          expect(DetermineAreaService).not_to receive(:run)
+        it "does not assign area" do
+          allow(DetermineEastingAndNorthingService).to receive(:run)
+          allow(DetermineAreaService).to receive(:run)
 
           described_class.run(address: address)
 
+          expect(DetermineEastingAndNorthingService).not_to have_received(:run)
+          expect(DetermineAreaService).not_to have_received(:run)
           expect(address.area).to be_nil
         end
       end
diff --git a/spec/services/waste_carriers_engine/determine_easting_and_northing_service_spec.rb b/spec/services/waste_carriers_engine/determine_easting_and_northing_service_spec.rb
index a81374225..c9a9892f5 100644
--- a/spec/services/waste_carriers_engine/determine_easting_and_northing_service_spec.rb
+++ b/spec/services/waste_carriers_engine/determine_easting_and_northing_service_spec.rb
@@ -1,15 +1,17 @@
+# frozen_string_literal: true
+
 # spec/services/waste_carriers_engine/determine_easting_and_northing_service_spec.rb
 
-require 'rails_helper'
+require "rails_helper"
 
 module WasteCarriersEngine
   RSpec.describe DetermineEastingAndNorthingService, type: :service do
-    let(:service) { DetermineEastingAndNorthingService.new }
-    let(:valid_postcode) { 'SW1A 1AA' }
-    let(:invalid_postcode) { 'INVALID' }
+    let(:service) { described_class.new }
+    let(:valid_postcode) { "SW1A 1AA" }
+    let(:invalid_postcode) { "INVALID" }
 
-    describe '#run' do
-      context 'when given a valid postcode' do
+    describe "#run" do
+      context "when given a valid postcode" do
         before do
           # Stub AddressLookupService to return a valid response
           allow(AddressLookupService).to receive(:run).with(valid_postcode).and_return(
@@ -17,7 +19,7 @@ module WasteCarriersEngine
           )
         end
 
-        it 'returns the correct easting and northing values' do
+        it "returns the correct easting and northing values" do
           result = service.run(postcode: valid_postcode)
 
           expect(result[:easting]).to eq(529_090.0)
@@ -25,7 +27,7 @@ module WasteCarriersEngine
         end
       end
 
-      context 'when given an invalid postcode' do
+      context "when given an invalid postcode" do
         before do
           # Stub AddressLookupService to return a NoMatchError
           allow(AddressLookupService).to receive(:run).with(invalid_postcode).and_return(
@@ -33,7 +35,7 @@ module WasteCarriersEngine
           )
         end
 
-        it 'returns the default easting and northing values' do
+        it "returns the default easting and northing values" do
           result = service.run(postcode: invalid_postcode)
 
           expect(result[:easting]).to eq(0.0)
@@ -41,15 +43,15 @@ module WasteCarriersEngine
         end
       end
 
-      context 'when the postcode lookup service returns an error' do
+      context "when the postcode lookup service returns an error" do
         before do
           # Stub AddressLookupService to return a generic error
           allow(AddressLookupService).to receive(:run).with(invalid_postcode).and_return(
-            instance_double(DefraRuby::Address::Response, successful?: false, error: StandardError.new('An error occurred'))
+            instance_double(DefraRuby::Address::Response, successful?: false, error: StandardError.new("An error occurred"))
           )
         end
 
-        it 'returns the default easting and northing values' do
+        it "returns the default easting and northing values" do
           result = service.run(postcode: invalid_postcode)
 
           expect(result[:easting]).to eq(0.0)