Fix skipped tests

I think there were a couple of issues: using the incorrect fixture,
and needing to add the placeholder string to the parts key

test/controllers/content_items_controller_test.rb

@@ -370,7 +370,6 @@ class ContentItemsControllerTest < ActionController::TestCase
     content_item["details"]["body"] = "{{ab_test_sa_video_stop_self_employed}}"
 
     stub_content_store_has_item(content_item["base_path"], content_item)
-
     request.headers["HTTP_GOVUK_ABTEST_SAVIDEOSTOPSELFEMPLOYED"] = nil
 
     get :show, params: { path: path_for(content_item) }
@@ -500,10 +499,15 @@ class ContentItemsControllerTest < ActionController::TestCase
   end
 
   test "AB test replaces content on the pay-weekly-monthly page with default" do
-    skip("Needs fixing")
-    content_item = content_store_has_schema_example("answer", "answer")
-    content_item["base_path"] = "/pay-self-assessment-tax-bill/pay-weekly-monthly"
-    content_item["details"]["body"] = "{{ab_test_sa_video_pay_bill}}"
+    # skip("Needs fixing")
+    content_item = govuk_content_schema_example("guide", "guide")
+    content_item["base_path"] = "/pay-self-assessment-tax-bill"
+    content_item["details"]["parts"] = []
+    parts = {
+      "body" => "{{ab_test_sa_video_pay_bill}}",
+      "slug" => "pay-weekly-monthly",
+    }
+    content_item["details"]["parts"] << parts
 
     stub_content_store_has_item(content_item["base_path"], content_item)
 
@@ -516,10 +520,15 @@ class ContentItemsControllerTest < ActionController::TestCase
   end
 
   test "AB test replaces content on the pay-weekly-monthly page with Variant A" do
-    skip("Needs fixing")
-    content_item = content_store_has_schema_example("answer", "answer")
-    content_item["base_path"] = "/pay-self-assessment-tax-bill/pay-weekly-monthly"
-    content_item["details"]["body"] = "{{ab_test_sa_video_pay_bill}}"
+    # skip("Needs fixing")
+    content_item = govuk_content_schema_example("guide", "guide")
+    content_item["base_path"] = "/pay-self-assessment-tax-bill"
+    content_item["details"]["parts"] = []
+    parts = {
+      "body" => "{{ab_test_sa_video_pay_bill}}",
+      "slug" => "pay-weekly-monthly",
+    }
+    content_item["details"]["parts"] << parts
 
     stub_content_store_has_item(content_item["base_path"], content_item)
 
@@ -532,20 +541,23 @@ class ContentItemsControllerTest < ActionController::TestCase
   end
 
   test "AB test replaces content on the pay-weekly-monthly page with Variant B" do
-    skip("Needs fixing")
-    content_item = content_store_has_schema_example("guide", "guide")
+    # skip("Needs fixing")
+    content_item = govuk_content_schema_example("guide", "guide")
     content_item["base_path"] = "/pay-self-assessment-tax-bill"
-    content_item["details"]["body"] = "{{ab_test_sa_video_pay_bill}}"
-    content_item["current_part_body"] = "{{ab_test_sa_video_pay_bill}}"
+    content_item["details"]["parts"] = []
+    parts = {
+      "body" => "{{ab_test_sa_video_pay_bill}}",
+      "slug" => "pay-weekly-monthly",
+    }
+    content_item["details"]["parts"] << parts
 
     stub_content_store_has_item(content_item["base_path"], content_item)
-
     request.headers["HTTP_GOVUK_ABTEST_SAVIDEOPAYBILL"] = "B"
 
     get :show, params: { path: path_for(content_item) }
     assert_response :success
     assert_no_match "{{ab_test_sa_video_pay_bill}}", response.body
-    assert_includes I18n.t("ab_tests.sa_video_pay_bill.B").to_s, response.body
+    assert_match I18n.t("ab_tests.sa_video_pay_bill.B").to_s, response.body
   end
 
   def path_for(content_item, locale = nil)