diff --git a/apps/admin-x-settings/src/components/settings/advanced/labs/private-features.tsx b/apps/admin-x-settings/src/components/settings/advanced/labs/private-features.tsx
index 05d4a20cfb2..c8a0dd5c1a2 100644
--- a/apps/admin-x-settings/src/components/settings/advanced/labs/private-features.tsx
+++ b/apps/admin-x-settings/src/components/settings/advanced/labs/private-features.tsx
@@ -59,6 +59,10 @@ const features: Feature[] = [{
     title: 'Retention Offers',
     description: 'Enable retention offers for canceling members',
     flag: 'retentionOffers'
+}, {
+    title: 'Welcome Email Editor',
+    description: 'Enable the new welcome email editor experience',
+    flag: 'welcomeEmailEditor'
 }];
 
 const AlphaFeatures: React.FC = () => {
diff --git a/apps/admin-x-settings/src/components/settings/growth/offers/edit-offer-modal.tsx b/apps/admin-x-settings/src/components/settings/growth/offers/edit-offer-modal.tsx
index 12a8aad2156..45897ad1680 100644
--- a/apps/admin-x-settings/src/components/settings/growth/offers/edit-offer-modal.tsx
+++ b/apps/admin-x-settings/src/components/settings/growth/offers/edit-offer-modal.tsx
@@ -142,6 +142,17 @@ const Sidebar: React.FC<{
                                     }}
                                     onKeyDown={() => clearError('name')}
                                 />
+                                <TextField
+                                    containerClassName='group'
+                                    error={Boolean(errors.code)}
+                                    hint={errors.code || (offer?.code !== '' ? <span className='truncate text-grey-700'>{homepageUrl}<span className='font-bold text-black dark:text-white'>{offer?.code}</span></span> : null)}
+                                    placeholder='black-friday'
+                                    rightPlaceholder={offer?.code !== '' ? <Button className='mr-0.5 mt-1' color='green' label={isCopied ? 'Copied!' : 'Copy link'} size='sm' onClick={handleCopyClick} /> : null}
+                                    title='Offer code'
+                                    value={offer?.code}
+                                    onChange={e => updateOffer({code: e.target.value})}
+                                    onKeyDown={() => clearError('code')}
+                                />
                                 <TextField
                                     error={Boolean(errors.displayTitle)}
                                     hint={errors.displayTitle}
@@ -157,15 +168,6 @@ const Sidebar: React.FC<{
                                     value={offer?.display_description}
                                     onChange={e => updateOffer({display_description: e.target.value})}
                                 />
-                                <TextField
-                                    error={Boolean(errors.code)}
-                                    hint={errors.code || (offer?.code !== '' ? <div className='flex items-center justify-between'><div>{homepageUrl}<span className='font-bold'>{offer?.code}</span></div><span></span><Button className='text-xs' color='green' label={`${isCopied ? 'Copied' : 'Copy'}`} size='sm' link onClick={handleCopyClick} /></div> : null)}
-                                    placeholder='black-friday'
-                                    title='Offer code'
-                                    value={offer?.code}
-                                    onChange={e => updateOffer({code: e.target.value})}
-                                    onKeyDown={() => clearError('code')}
-                                />
                             </div>
                         </section>
                     </Form>
diff --git a/apps/admin/src/assets/images/ghost-pro-logo-dark.png b/apps/admin/src/assets/images/ghost-pro-logo-dark.png
new file mode 100644
index 00000000000..bc6f3124d11
Binary files /dev/null and b/apps/admin/src/assets/images/ghost-pro-logo-dark.png differ
diff --git a/apps/admin/src/layout/app-sidebar/app-sidebar-content.tsx b/apps/admin/src/layout/app-sidebar/app-sidebar-content.tsx
index 7f580ddbd36..8800b271706 100644
--- a/apps/admin/src/layout/app-sidebar/app-sidebar-content.tsx
+++ b/apps/admin/src/layout/app-sidebar/app-sidebar-content.tsx
@@ -1,6 +1,7 @@
 import {
     SidebarContent,
 } from "@tryghost/shade"
+import type { ReactNode } from "react";
 
 import WhatsNewBanner from "@/whats-new/components/whats-new-banner";
 
@@ -11,20 +12,42 @@ import NavSettings from "./nav-settings";
 import ThemeErrorsBanner from "./theme-errors-banner";
 import UpgradeBanner from "./upgrade-banner";
 import { useUpgradeStatus } from "./hooks/use-upgrade-status";
+import { useWhatsNewStatus } from "./hooks/use-whats-new-status";
+import { useActiveThemeErrors } from "./hooks/use-theme-errors";
 
 function AppSidebarContent() {
+    const {hasErrors} = useActiveThemeErrors();
     const { showUpgradeBanner, trialDaysRemaining } = useUpgradeStatus();
+    const { showWhatsNewBanner } = useWhatsNewStatus();
+    let banner: ReactNode = null;
+    let bannerContainerClassName = '';
+
+    if (hasErrors) {
+        banner = <ThemeErrorsBanner />;
+        bannerContainerClassName = 'pb-[110px]';
+    } else {
+        if (showUpgradeBanner) {
+            banner = <UpgradeBanner trialDaysRemaining={trialDaysRemaining} />;
+            bannerContainerClassName = 'pb-[254px]';
+        } else if (showWhatsNewBanner) {
+            banner = <WhatsNewBanner />;
+            bannerContainerClassName = 'pb-[180px]';
+        }
+    }
 
     return (
-        <SidebarContent className="px-3 pt-4 justify-between">
+        <SidebarContent className={`px-3 pt-4 ${!banner && 'justify-between'}`}>
             <div className="flex flex-col gap-2 sidebar:gap-4">
                 <NavMain />
                 <NavContent />
                 <NavGhostPro />
             </div>
-            <div className="flex flex-col gap-2 sidebar:gap-4">
-                {showUpgradeBanner ? <UpgradeBanner trialDaysRemaining={trialDaysRemaining} /> : <WhatsNewBanner />}
-                <ThemeErrorsBanner />
+            <div className={`flex flex-col gap-2 sidebar:gap-4 ${bannerContainerClassName}`}>
+                {banner &&
+                    <div className="fixed left-3 bottom-[92px] max-w-[276px] z-50">
+                        {banner}
+                    </div>
+                }
                 <NavSettings className="pb-0" />
             </div>
         </SidebarContent>
diff --git a/apps/admin/src/layout/app-sidebar/app-sidebar-footer.tsx b/apps/admin/src/layout/app-sidebar/app-sidebar-footer.tsx
index fd11dd79fcd..45047f68dfd 100644
--- a/apps/admin/src/layout/app-sidebar/app-sidebar-footer.tsx
+++ b/apps/admin/src/layout/app-sidebar/app-sidebar-footer.tsx
@@ -8,13 +8,21 @@ import {
 } from "@tryghost/shade"
 import WhatsNewDialog from "@/whats-new/components/whats-new-dialog";
 import { UserMenu } from "./user-menu";
+import { useUpgradeStatus } from "./hooks/use-upgrade-status";
+import { useWhatsNewStatus } from "./hooks/use-whats-new-status";
+import { useActiveThemeErrors } from "./hooks/use-theme-errors";
 
 function AppSidebarFooter({ ...props }: React.ComponentProps<typeof SidebarFooter>) {
     const [isWhatsNewDialogOpen, setIsWhatsNewDialogOpen] = useState(false);
+    const { showUpgradeBanner } = useUpgradeStatus();
+    const { showWhatsNewBanner } = useWhatsNewStatus();
+    const {hasErrors} = useActiveThemeErrors();
+    const banner = showUpgradeBanner || showWhatsNewBanner || hasErrors;
+
     return (
         <>
             <SidebarFooter {...props}>
-                <SidebarGroup>
+                <SidebarGroup className={banner ? 'pt-3' : ''}>
                     <SidebarMenu>
                         <SidebarMenuItem>
                             <UserMenu onOpenWhatsNew={() => setIsWhatsNewDialogOpen(true)} />
diff --git a/apps/admin/src/layout/app-sidebar/hooks/use-whats-new-status.ts b/apps/admin/src/layout/app-sidebar/hooks/use-whats-new-status.ts
new file mode 100644
index 00000000000..5b84d2caa75
--- /dev/null
+++ b/apps/admin/src/layout/app-sidebar/hooks/use-whats-new-status.ts
@@ -0,0 +1,16 @@
+import { useChangelog } from "@/whats-new/hooks/use-changelog";
+import { useWhatsNew } from "@/whats-new/hooks/use-whats-new";
+
+export interface WhatsNewStatus {
+    showWhatsNewBanner: boolean;
+}
+
+export function useWhatsNewStatus(): WhatsNewStatus {
+    const { data: whatsNewData } = useWhatsNew();
+    const { data: changelog } = useChangelog();
+    const latestEntry = changelog?.entries[0];
+
+    return {
+        showWhatsNewBanner: !!whatsNewData?.hasNew && !!latestEntry,
+    };
+}
diff --git a/apps/admin/src/layout/app-sidebar/theme-errors-banner.tsx b/apps/admin/src/layout/app-sidebar/theme-errors-banner.tsx
index 4a8c3a48b87..54f72f2f730 100644
--- a/apps/admin/src/layout/app-sidebar/theme-errors-banner.tsx
+++ b/apps/admin/src/layout/app-sidebar/theme-errors-banner.tsx
@@ -24,7 +24,7 @@ function ThemeErrorsBanner() {
                     <LucideIcon.AlertTriangle className="mt-0.5 size-4 shrink-0 text-red" />
                     <div>
                         <div className="font-semibold text-red">Your theme has errors</div>
-                        <div className="text-sm text-muted-foreground">Some functionality on your site may be limited &rarr;</div>
+                        <div className="text-sm text-foreground">Some functionality on your site may be limited &rarr;</div>
                     </div>
                 </div>
             </Banner>
diff --git a/apps/admin/src/layout/app-sidebar/upgrade-banner.tsx b/apps/admin/src/layout/app-sidebar/upgrade-banner.tsx
index 56ec91207b5..40f4aef0924 100644
--- a/apps/admin/src/layout/app-sidebar/upgrade-banner.tsx
+++ b/apps/admin/src/layout/app-sidebar/upgrade-banner.tsx
@@ -4,16 +4,18 @@ import {
 } from "@tryghost/shade"
 
 import ghostProLogo from "@/assets/images/ghost-pro-logo.png";
+import ghostProLogoDark from "@/assets/images/ghost-pro-logo-dark.png";
 
 function UpgradeBanner({ trialDaysRemaining }: { trialDaysRemaining: number }) {
     return (
-        <Banner variant='gradient' size='lg' className="mx-2 my-5 flex flex-col items-stretch">
+        <Banner variant='gradient' size='lg' className="mx-2 flex flex-col items-stretch">
             <div>
-                <img src={ghostProLogo} alt="Ghost Pro" className="max-h-[33px]" />
+                <img src={ghostProLogo} alt="Ghost Pro" className="max-h-[33px] dark:hidden" />
+                <img src={ghostProLogoDark} alt="Ghost Pro" className="max-h-[33px] hidden dark:block" />
             </div>
             <div className="text-base mt-3 font-semibold">Unlock every feature</div>
             <div className="mt-2 text-gray-700 text-sm mb-4">
-                Choose a plan to access the full power of Ghost right away, you have <span className="font-semibold text-black">{trialDaysRemaining} days</span> free trial remaining.
+                Choose a plan to access the full power of Ghost right away, you have <span className="font-semibold text-foreground">{trialDaysRemaining} days</span> free trial remaining.
             </div>
             <Button asChild><a href="#/pro/billing/plans">Upgrade now</a></Button>
         </Banner>
diff --git a/apps/admin/src/whats-new/components/whats-new-banner.tsx b/apps/admin/src/whats-new/components/whats-new-banner.tsx
index 40cd51eb426..a2044ee997f 100644
--- a/apps/admin/src/whats-new/components/whats-new-banner.tsx
+++ b/apps/admin/src/whats-new/components/whats-new-banner.tsx
@@ -49,10 +49,10 @@ function WhatsNewBanner() {
                 data-test-toast-link
             >
                 <div className="flex items-center gap-2 mb-2">
-                    <LucideIcon.Sparkles className="size-4 text-purple-600" />
-                    <span className="text-xs font-semibold text-gray-700 uppercase tracking-wide">What’s new?</span>
+                    <LucideIcon.Sparkles className="size-4 text-purple-600 dark:text-purple" />
+                    <span className="text-xs font-semibold text-gray-700 dark:text-gray-400 uppercase tracking-wide">What’s new?</span>
                 </div>
-                <div className="text-base font-semibold text-gray-900 mb-1" data-test-toast-title>
+                <div className="text-base font-semibold text-gray-900 dark:text-foreground mb-1" data-test-toast-title>
                     {latestEntry.title}
                 </div>
                 <div className="text-sm text-gray-700" data-test-toast-excerpt>
diff --git a/apps/shade/src/components/ui/banner.tsx b/apps/shade/src/components/ui/banner.tsx
index 10d5af676a5..4dd240f15dc 100644
--- a/apps/shade/src/components/ui/banner.tsx
+++ b/apps/shade/src/components/ui/banner.tsx
@@ -9,17 +9,19 @@ const bannerVariants = cva(
     {
         variants: {
             variant: {
-                default: 'border border-border bg-background shadow-sm hover:shadow-md',
+                default: 'border border-border bg-background shadow-sm hover:shadow-md dark:border-gray-900 dark:bg-gray-925',
                 gradient: [
-                    'cursor-pointer border border-gray-100 bg-white',
+                    'cursor-pointer border border-gray-100 bg-white dark:border-gray-950 dark:bg-black',
                     'shadow-[rgb(75_225_226_/_28%)_-7px_-6px_42px_8px,rgb(202_103_255_/_32%)_7px_6px_42px_8px]',
+                    'dark:shadow-[rgb(75_225_226_/_36%)_-7px_-6px_42px_8px,rgb(202_103_255_/_38%)_7px_6px_42px_8px]',
                     'hover:shadow-[rgb(75_225_226_/_38%)_-7px_-4px_42px_10px,rgb(202_103_255_/_42%)_7px_8px_42px_10px]',
+                    'dark:hover:shadow-[rgb(75_225_226_/_50%)_-7px_-4px_42px_10px,rgb(202_103_255_/_52%)_7px_8px_42px_10px]',
                     'hover:translate-y-[-2px] hover:scale-[1.01]'
                 ],
                 info: 'bg-blue-50 border-blue-200 dark:bg-blue-950/30 dark:border-blue-800 border',
                 success: 'bg-green-50 border-green-200 dark:bg-green-950/30 dark:border-green-800 border',
                 warning: 'bg-yellow-50 border-yellow-200 dark:bg-yellow-950/30 dark:border-yellow-800 border',
-                destructive: 'bg-white shadow-sm dark:bg-black'
+                destructive: 'bg-white shadow-sm dark:bg-gray-950'
             },
             size: {
                 sm: 'p-2 text-sm',
@@ -85,7 +87,7 @@ const Banner = React.forwardRef<HTMLDivElement, BannerProps>(
                 {dismissible && (
                     <Button
                         aria-label="Dismiss notification"
-                        className="absolute right-1 top-1 size-8 text-gray-600"
+                        className="absolute right-1 top-1 size-8 text-gray-600 dark:text-gray-500 dark:hover:text-gray-300"
                         size="icon"
                         variant="ghost"
                         onClick={handleDismiss}
diff --git a/ghost/core/core/shared/labs.js b/ghost/core/core/shared/labs.js
index 02f9eef6705..efd61e4ae6d 100644
--- a/ghost/core/core/shared/labs.js
+++ b/ghost/core/core/shared/labs.js
@@ -51,7 +51,8 @@ const PRIVATE_FEATURES = [
     'themeTranslation',
     'indexnow',
     'transistor',
-    'retentionOffers'
+    'retentionOffers',
+    'welcomeEmailEditor'
 ];
 
 module.exports.GA_KEYS = [...GA_FEATURES];
diff --git a/ghost/core/test/e2e-api/admin/__snapshots__/config.test.js.snap b/ghost/core/test/e2e-api/admin/__snapshots__/config.test.js.snap
index 97690aed12b..5de87f5d556 100644
--- a/ghost/core/test/e2e-api/admin/__snapshots__/config.test.js.snap
+++ b/ghost/core/test/e2e-api/admin/__snapshots__/config.test.js.snap
@@ -31,6 +31,7 @@ Object {
       "transistor": true,
       "urlCache": true,
       "webmentions": true,
+      "welcomeEmailEditor": true,
       "welcomeEmails": true,
     },
     "mail": "",
diff --git a/ghost/core/test/e2e-browser/portal/upgrade.spec.js b/ghost/core/test/e2e-browser/portal/upgrade.spec.js
index 41c14c4e59d..76ef1a7d50d 100644
--- a/ghost/core/test/e2e-browser/portal/upgrade.spec.js
+++ b/ghost/core/test/e2e-browser/portal/upgrade.spec.js
@@ -33,7 +33,7 @@ test.describe('Portal', () => {
                     delay: 500
                 });
 
-                await sharedPage.waitForLoadState('networkidle');
+                await expect(sharedPage.locator('[data-test-tier]').first()).toBeVisible();
                 await impersonateMember(sharedPage);
 
                 const portalTriggerButton = sharedPage.frameLocator('[data-testid="portal-trigger-frame"]').locator('[data-testid="portal-trigger-button"]');
@@ -50,8 +50,9 @@ test.describe('Portal', () => {
                 await completeStripeSubscription(sharedPage);
 
                 // open portal and check that member has been upgraded to paid tier
+                await expect(portalTriggerButton).toBeVisible();
                 await portalTriggerButton.click();
-                await expect(portalFrame.getByText('$50.00/year')).toBeVisible();
+                await expect(portalFrame.getByText('$50.00/year')).toBeVisible({timeout: 30000});
                 await expect(portalFrame.getByRole('heading', {name: 'Billing info'})).toBeVisible();
                 await expect(portalFrame.getByText('**** **** **** 4242')).toBeVisible();
 
@@ -102,10 +103,11 @@ test.describe('Portal', () => {
                 await completeStripeSubscription(sharedPage);
 
                 // open portal and check that member has been upgraded to paid tier
+                await expect(portalTriggerButton).toBeVisible();
                 await portalTriggerButton.click();
                 // verify member's tier, price and card details
                 await expect(portalFrame.getByText(tierName)).toBeVisible();
-                await expect(portalFrame.getByText('$50.00/year')).toBeVisible();
+                await expect(portalFrame.getByText('$50.00/year')).toBeVisible({timeout: 30000});
                 await expect(portalFrame.getByText('**** **** **** 4242')).toBeVisible();
 
                 // verify member's tier on member detail page in admin
diff --git a/ghost/core/test/e2e-browser/utils/e2e-browser-utils.js b/ghost/core/test/e2e-browser/utils/e2e-browser-utils.js
index 1ab8a7c06af..c7d6468fcd1 100644
--- a/ghost/core/test/e2e-browser/utils/e2e-browser-utils.js
+++ b/ghost/core/test/e2e-browser/utils/e2e-browser-utils.js
@@ -277,15 +277,14 @@ const createOffer = async (page, {name, tierName, offerType, amount, discountTyp
 
             const confirmModal = await page.getByTestId('confirmation-modal');
             await confirmModal.getByRole('button', {name: 'Archive'}).click();
-        }
+            await confirmModal.waitFor({state: 'hidden'});
 
-        if (isCTA) {
+            // Still in the offers modal after archiving — click "New offer" directly
+            await page.getByText('New offer').click();
+        } else if (await page.getByTestId('offers').getByRole('button', {name: 'Add offer'}).isVisible()) {
             await page.getByTestId('offers').getByRole('button', {name: 'Add offer'}).click();
         } else {
-            // ensure the modal is open
-            if (!page.getByTestId('offers-modal').isVisible()) {
-                await page.getByTestId('offers').getByRole('button', {name: 'Manage offers'}).click();
-            }
+            await page.getByTestId('offers').getByRole('button', {name: 'Manage offers'}).click();
             await page.getByText('New offer').click();
         }
 
diff --git a/ghost/core/test/integration/exporter/exporter.test.js b/ghost/core/test/integration/exporter/exporter.test.js
index d6b7ad6c76b..dc4ab4e6333 100644
--- a/ghost/core/test/integration/exporter/exporter.test.js
+++ b/ghost/core/test/integration/exporter/exporter.test.js
@@ -110,7 +110,11 @@ describe('Exporter', function () {
             // NOTE: using `Object.keys` here instead of `should.have.only.keys` assertion
             //       because when `have.only.keys` fails there's no useful diff
             assert.deepEqual(Object.keys(exportData.data).sort(), tables.sort());
-            Object.keys(exportData.data).sort().should.containDeep(Object.keys(exportedBodyLatest().db[0].data));
+            assert(
+                Object.keys(exportedBodyLatest().db[0].data).every(key => (
+                    Object.hasOwnProperty.call(exportData.data, key)
+                ))
+            );
             assert.equal(exportData.meta.version, ghostVersion.full);
 
             // excludes table should contain no data
diff --git a/ghost/core/test/integration/importer/v5.js b/ghost/core/test/integration/importer/v5.js
index ab8bdd3d044..6f839273c32 100644
--- a/ghost/core/test/integration/importer/v5.js
+++ b/ghost/core/test/integration/importer/v5.js
@@ -73,7 +73,7 @@ describe('Importing 5.x export', function () {
 
         // Imported user
         assert.equal(user2.email, 'import-test-user@ghost.org');
-        user2.id.should.not.equal(LEGACY_HARDCODED_USER_ID);
+        assert.notEqual(user2.id, LEGACY_HARDCODED_USER_ID);
 
         assert.equal(posts.data.length, 2);
 
diff --git a/ghost/core/test/legacy/api/admin/db.test.js b/ghost/core/test/legacy/api/admin/db.test.js
index 275bfd524ab..ea8b2463572 100644
--- a/ghost/core/test/legacy/api/admin/db.test.js
+++ b/ghost/core/test/legacy/api/admin/db.test.js
@@ -308,8 +308,8 @@ describe('DB API', function () {
         assert.equal(res2.body.posts.length, 1);
 
         // Ensure the author is not imported with the legacy hardcoded user id
-        res2.body.posts[0].authors[0].id.should.not.equal(LEGACY_HARDCODED_USER_ID);
-        res2.body.posts[0].primary_author.id.should.not.equal(LEGACY_HARDCODED_USER_ID);
+        assert.notEqual(res2.body.posts[0].authors[0].id, LEGACY_HARDCODED_USER_ID);
+        assert.notEqual(res2.body.posts[0].primary_author.id, LEGACY_HARDCODED_USER_ID);
 
         const usersResponse = await request.get(localUtils.API.getApiQuery('users/'))
             .set('Origin', config.get('url'))
@@ -320,9 +320,9 @@ describe('DB API', function () {
         assert.equal(usersResponse.body.users.length, 3);
 
         // Ensure user is not imported with the legacy hardcoded user id
-        usersResponse.body.users[0].id.should.not.equal(LEGACY_HARDCODED_USER_ID);
-        usersResponse.body.users[1].id.should.not.equal(LEGACY_HARDCODED_USER_ID);
-        usersResponse.body.users[2].id.should.not.equal(LEGACY_HARDCODED_USER_ID);
+        assert.notEqual(usersResponse.body.users[0].id, LEGACY_HARDCODED_USER_ID);
+        assert.notEqual(usersResponse.body.users[1].id, LEGACY_HARDCODED_USER_ID);
+        assert.notEqual(usersResponse.body.users[2].id, LEGACY_HARDCODED_USER_ID);
     });
 
     it('Can import a JSON database with products', async function () {
diff --git a/ghost/core/test/legacy/models/model-posts.test.js b/ghost/core/test/legacy/models/model-posts.test.js
index 0a83d6d3138..a4af25c32b0 100644
--- a/ghost/core/test/legacy/models/model-posts.test.js
+++ b/ghost/core/test/legacy/models/model-posts.test.js
@@ -773,7 +773,7 @@ describe('Post Model', function () {
                     assert(publishedPost.get('published_at') instanceof Date);
                     assert.equal(publishedPost.get('published_by'), testUtils.DataGenerator.Content.users[0].id);
                     assert(publishedPost.get('updated_at') instanceof Date);
-                    publishedPost.get('updated_at').should.not.equal(createdPostUpdatedDate);
+                    assert.notEqual(publishedPost.get('updated_at'), createdPostUpdatedDate);
 
                     assert.equal(Object.keys(eventsTriggered).length, 4);
                     assertExists(eventsTriggered['post.published']);
@@ -842,7 +842,7 @@ describe('Post Model', function () {
                     assert(publishedPost.get('published_at') instanceof Date);
                     assert.equal(publishedPost.get('published_by'), testUtils.DataGenerator.Content.users[0].id);
                     assert(publishedPost.get('updated_at') instanceof Date);
-                    publishedPost.get('updated_at').should.not.equal(createdPostUpdatedDate);
+                    assert.notEqual(publishedPost.get('updated_at'), createdPostUpdatedDate);
 
                     assert.equal(Object.keys(eventsTriggered).length, 4);
                     assertExists(eventsTriggered['post.published']);
@@ -1105,9 +1105,9 @@ describe('Post Model', function () {
                         }, context);
                     }).then(function (updatedSecondPost) {
                     // Should have updated from original
-                        updatedSecondPost.get('slug').should.not.equal(secondPost.slug);
+                        assert.notEqual(updatedSecondPost.get('slug'), secondPost.slug);
                         // Should not have a conflicted slug from the first
-                        updatedSecondPost.get('slug').should.not.equal(firstPost.slug);
+                        assert.notEqual(updatedSecondPost.get('slug'), firstPost.slug);
 
                         assert.equal(Object.keys(eventsTriggered).length, 3);
                         assertExists(eventsTriggered['post.edited']);
@@ -1118,9 +1118,9 @@ describe('Post Model', function () {
                         });
                     }).then(function (foundPost) {
                     // Should have updated from original
-                        foundPost.get('slug').should.not.equal(secondPost.slug);
+                        assert.notEqual(foundPost.get('slug'), secondPost.slug);
                         // Should not have a conflicted slug from the first
-                        foundPost.get('slug').should.not.equal(firstPost.slug);
+                        assert.notEqual(foundPost.get('slug'), firstPost.slug);
 
                         done();
                     }).catch(done);
diff --git a/ghost/core/test/legacy/models/model-users.test.js b/ghost/core/test/legacy/models/model-users.test.js
index d62f1ed9621..7a014224e1e 100644
--- a/ghost/core/test/legacy/models/model-users.test.js
+++ b/ghost/core/test/legacy/models/model-users.test.js
@@ -37,7 +37,7 @@ describe('User Model', function run() {
 
             UserModel.add(userData, context).then(function (createdUser) {
                 assertExists(createdUser);
-                createdUser.attributes.password.should.not.equal(userData.password, 'password was hashed');
+                assert.notEqual(createdUser.attributes.password, userData.password, 'password was hashed');
                 assert.equal(createdUser.attributes.email, userData.email, 'email address correct');
 
                 done();
@@ -244,7 +244,7 @@ describe('User Model', function run() {
                 return UserModel.add(userData, _.extend({}, context, {withRelated: ['roles']}));
             }).then(function (createdUser) {
                 assertExists(createdUser);
-                createdUser.get('password').should.not.equal(userData.password, 'password was hashed');
+                assert.notEqual(createdUser.get('password'), userData.password, 'password was hashed');
                 assert.equal(createdUser.get('email'), userData.email, 'email address correct');
                 assert.equal(createdUser.related('roles').toJSON()[0].name, 'Administrator', 'role set correctly');
 
diff --git a/ghost/core/test/unit/frontend/helpers/get.test.js b/ghost/core/test/unit/frontend/helpers/get.test.js
index 8e04a4d9104..67a6209e75b 100644
--- a/ghost/core/test/unit/frontend/helpers/get.test.js
+++ b/ghost/core/test/unit/frontend/helpers/get.test.js
@@ -389,8 +389,8 @@ describe('{{#get}} helper', function () {
 
         it('handles Date values', function () {
             const result = querySimplePath(data, 'post.published_at');
-            result.should.have.length(1);
-            result[0].should.be.a.Date();
+            assert.equal(result.length, 1);
+            assert(result[0] instanceof Date);
         });
 
         it('throws on recursive descent syntax', function () {
diff --git a/ghost/core/test/unit/frontend/meta/og-image.test.js b/ghost/core/test/unit/frontend/meta/og-image.test.js
index f56dc81a2aa..b857dddd07e 100644
--- a/ghost/core/test/unit/frontend/meta/og-image.test.js
+++ b/ghost/core/test/unit/frontend/meta/og-image.test.js
@@ -22,13 +22,11 @@ describe('getOgImage', function () {
         localSettingsCache.og_image = '/content/images/settings-og.jpg';
         localSettingsCache.cover_image = '/content/images/settings-cover.jpg';
 
-        getOgImage({context: ['home'], home: {}})
-            .should.endWith('/content/images/settings-og.jpg');
+        assert(getOgImage({context: ['home'], home: {}}).endsWith('/content/images/settings-og.jpg'));
 
         localSettingsCache.og_image = '';
 
-        getOgImage({context: ['home'], home: {}})
-            .should.endWith('/content/images/settings-cover.jpg');
+        assert(getOgImage({context: ['home'], home: {}}).endsWith('/content/images/settings-cover.jpg'));
 
         localSettingsCache.cover_image = '';
 
@@ -44,13 +42,11 @@ describe('getOgImage', function () {
             feature_image: '/content/images/post-feature.jpg'
         };
 
-        getOgImage({context: ['post'], post})
-            .should.endWith('post-og.jpg');
+        assert(getOgImage({context: ['post'], post}).endsWith('post-og.jpg'));
 
         post.og_image = '';
 
-        getOgImage({context: ['post'], post})
-            .should.endWith('post-feature.jpg');
+        assert(getOgImage({context: ['post'], post}).endsWith('post-feature.jpg'));
 
         post.feature_image = '';
 
@@ -74,13 +70,11 @@ describe('getOgImage', function () {
             feature_image: '/content/images/page-feature.jpg'
         };
 
-        getOgImage({context: ['page'], page})
-            .should.endWith('page-og.jpg');
+        assert(getOgImage({context: ['page'], page}).endsWith('page-og.jpg'));
 
         page.og_image = '';
 
-        getOgImage({context: ['page'], page})
-            .should.endWith('page-feature.jpg');
+        assert(getOgImage({context: ['page'], page}).endsWith('page-feature.jpg'));
 
         page.feature_image = '';
 
@@ -104,13 +98,11 @@ describe('getOgImage', function () {
             feature_image: '/content/images/page-feature.jpg'
         };
 
-        getOgImage({context: ['page'], post})
-            .should.endWith('page-og.jpg');
+        assert(getOgImage({context: ['page'], post}).endsWith('page-og.jpg'));
 
         post.og_image = '';
 
-        getOgImage({context: ['page'], post})
-            .should.endWith('page-feature.jpg');
+        assert(getOgImage({context: ['page'], post}).endsWith('page-feature.jpg'));
 
         post.feature_image = '';
 
@@ -133,8 +125,7 @@ describe('getOgImage', function () {
             cover_image: '/content/images/author-cover.jpg'
         };
 
-        getOgImage({context: ['author'], author})
-            .should.endWith('author-cover.jpg');
+        assert(getOgImage({context: ['author'], author}).endsWith('author-cover.jpg'));
 
         author.cover_image = '';
 
@@ -149,8 +140,7 @@ describe('getOgImage', function () {
             cover_image: '/content/images/author-cover.jpg'
         };
 
-        getOgImage({context: ['author', 'paged'], author})
-            .should.endWith('author-cover.jpg');
+        assert(getOgImage({context: ['author', 'paged'], author}).endsWith('author-cover.jpg'));
 
         author.cover_image = '';
 
@@ -165,13 +155,11 @@ describe('getOgImage', function () {
             feature_image: '/content/images/tag-feature.jpg'
         };
 
-        getOgImage({context: ['tag'], tag})
-            .should.endWith('tag-feature.jpg');
+        assert(getOgImage({context: ['tag'], tag}).endsWith('tag-feature.jpg'));
 
         tag.feature_image = '';
 
-        getOgImage({context: ['tag'], tag})
-            .should.endWith('settings-cover.jpg');
+        assert(getOgImage({context: ['tag'], tag}).endsWith('settings-cover.jpg'));
 
         localSettingsCache.cover_image = '';
 
@@ -186,13 +174,11 @@ describe('getOgImage', function () {
             feature_image: '/content/images/tag-feature.jpg'
         };
 
-        getOgImage({context: ['tag', 'paged'], tag})
-            .should.endWith('tag-feature.jpg');
+        assert(getOgImage({context: ['tag', 'paged'], tag}).endsWith('tag-feature.jpg'));
 
         tag.feature_image = '';
 
-        getOgImage({context: ['tag', 'paged'], tag})
-            .should.endWith('settings-cover.jpg');
+        assert(getOgImage({context: ['tag', 'paged'], tag}).endsWith('settings-cover.jpg'));
 
         localSettingsCache.cover_image = '';
 
diff --git a/ghost/core/test/unit/frontend/meta/twitter-image.test.js b/ghost/core/test/unit/frontend/meta/twitter-image.test.js
index 82d7a016102..44ee7ba1725 100644
--- a/ghost/core/test/unit/frontend/meta/twitter-image.test.js
+++ b/ghost/core/test/unit/frontend/meta/twitter-image.test.js
@@ -22,13 +22,11 @@ describe('getTwitterImage', function () {
         localSettingsCache.twitter_image = '/content/images/settings-twitter.jpg';
         localSettingsCache.cover_image = '/content/images/settings-cover.jpg';
 
-        getTwitterImage({context: ['home'], home: {}})
-            .should.endWith('/content/images/settings-twitter.jpg');
+        assert(getTwitterImage({context: ['home'], home: {}}).endsWith('/content/images/settings-twitter.jpg'));
 
         localSettingsCache.twitter_image = '';
 
-        getTwitterImage({context: ['home'], home: {}})
-            .should.endWith('/content/images/settings-cover.jpg');
+        assert(getTwitterImage({context: ['home'], home: {}}).endsWith('/content/images/settings-cover.jpg'));
 
         localSettingsCache.cover_image = '';
 
@@ -44,13 +42,11 @@ describe('getTwitterImage', function () {
             feature_image: '/content/images/post-feature.jpg'
         };
 
-        getTwitterImage({context: ['post'], post})
-            .should.endWith('post-twitter.jpg');
+        assert(getTwitterImage({context: ['post'], post}).endsWith('post-twitter.jpg'));
 
         post.twitter_image = '';
 
-        getTwitterImage({context: ['post'], post})
-            .should.endWith('post-feature.jpg');
+        assert(getTwitterImage({context: ['post'], post}).endsWith('post-feature.jpg'));
 
         post.feature_image = '';
 
@@ -74,13 +70,11 @@ describe('getTwitterImage', function () {
             feature_image: '/content/images/page-feature.jpg'
         };
 
-        getTwitterImage({context: ['page'], page})
-            .should.endWith('page-twitter.jpg');
+        assert(getTwitterImage({context: ['page'], page}).endsWith('page-twitter.jpg'));
 
         page.twitter_image = '';
 
-        getTwitterImage({context: ['page'], page})
-            .should.endWith('page-feature.jpg');
+        assert(getTwitterImage({context: ['page'], page}).endsWith('page-feature.jpg'));
 
         page.feature_image = '';
 
@@ -104,13 +98,11 @@ describe('getTwitterImage', function () {
             feature_image: '/content/images/page-feature.jpg'
         };
 
-        getTwitterImage({context: ['page'], post})
-            .should.endWith('page-twitter.jpg');
+        assert(getTwitterImage({context: ['page'], post}).endsWith('page-twitter.jpg'));
 
         post.twitter_image = '';
 
-        getTwitterImage({context: ['page'], post})
-            .should.endWith('page-feature.jpg');
+        assert(getTwitterImage({context: ['page'], post}).endsWith('page-feature.jpg'));
 
         post.feature_image = '';
 
@@ -133,8 +125,7 @@ describe('getTwitterImage', function () {
             cover_image: '/content/images/author-cover.jpg'
         };
 
-        getTwitterImage({context: ['author'], author})
-            .should.endWith('author-cover.jpg');
+        assert(getTwitterImage({context: ['author'], author}).endsWith('author-cover.jpg'));
 
         author.cover_image = '';
 
@@ -149,8 +140,7 @@ describe('getTwitterImage', function () {
             cover_image: '/content/images/author-cover.jpg'
         };
 
-        getTwitterImage({context: ['author', 'paged'], author})
-            .should.endWith('author-cover.jpg');
+        assert(getTwitterImage({context: ['author', 'paged'], author}).endsWith('author-cover.jpg'));
 
         author.cover_image = '';
 
@@ -165,13 +155,11 @@ describe('getTwitterImage', function () {
             feature_image: '/content/images/tag-feature.jpg'
         };
 
-        getTwitterImage({context: ['tag'], tag})
-            .should.endWith('tag-feature.jpg');
+        assert(getTwitterImage({context: ['tag'], tag}).endsWith('tag-feature.jpg'));
 
         tag.feature_image = '';
 
-        getTwitterImage({context: ['tag'], tag})
-            .should.endWith('settings-cover.jpg');
+        assert(getTwitterImage({context: ['tag'], tag}).endsWith('settings-cover.jpg'));
 
         localSettingsCache.cover_image = '';
 
@@ -186,13 +174,11 @@ describe('getTwitterImage', function () {
             feature_image: '/content/images/tag-feature.jpg'
         };
 
-        getTwitterImage({context: ['tag', 'paged'], tag})
-            .should.endWith('tag-feature.jpg');
+        assert(getTwitterImage({context: ['tag', 'paged'], tag}).endsWith('tag-feature.jpg'));
 
         tag.feature_image = '';
 
-        getTwitterImage({context: ['tag', 'paged'], tag})
-            .should.endWith('settings-cover.jpg');
+        assert(getTwitterImage({context: ['tag', 'paged'], tag}).endsWith('settings-cover.jpg'));
 
         localSettingsCache.cover_image = '';
 
diff --git a/ghost/core/test/unit/frontend/services/routing/static-routes-router.test.js b/ghost/core/test/unit/frontend/services/routing/static-routes-router.test.js
index b9b9f6fcf0c..be41ac3896c 100644
--- a/ghost/core/test/unit/frontend/services/routing/static-routes-router.test.js
+++ b/ghost/core/test/unit/frontend/services/routing/static-routes-router.test.js
@@ -85,7 +85,7 @@ describe('UNIT - services/routing/StaticRoutesRouter', function () {
             res.routerOptions.should.have.properties('type', 'templates', 'defaultTemplate', 'context', 'data', 'contentType');
             assert.equal(res.routerOptions.type, 'custom');
             assert.deepEqual(res.routerOptions.templates, []);
-            res.routerOptions.defaultTemplate.should.be.a.Function();
+            assert.equal(typeof res.routerOptions.defaultTemplate, 'function');
             assert.deepEqual(res.routerOptions.context, ['about']);
             assert.deepEqual(res.routerOptions.data, {});
 
@@ -102,7 +102,7 @@ describe('UNIT - services/routing/StaticRoutesRouter', function () {
             res.routerOptions.should.have.properties('type', 'templates', 'defaultTemplate', 'context', 'data', 'contentType');
             assert.equal(res.routerOptions.type, 'custom');
             assert.deepEqual(res.routerOptions.templates, []);
-            res.routerOptions.defaultTemplate.should.be.a.Function();
+            assert.equal(typeof res.routerOptions.defaultTemplate, 'function');
             assert.deepEqual(res.routerOptions.context, ['index']);
             assert.deepEqual(res.routerOptions.data, {});
 
diff --git a/ghost/core/test/unit/frontend/services/theme-engine/active.test.js b/ghost/core/test/unit/frontend/services/theme-engine/active.test.js
index 53a0069492a..46867f1cbba 100644
--- a/ghost/core/test/unit/frontend/services/theme-engine/active.test.js
+++ b/ghost/core/test/unit/frontend/services/theme-engine/active.test.js
@@ -68,7 +68,7 @@ describe('Themes', function () {
                 assert.equal(configStub.calledWith('assetHash', null), true);
 
                 // Check the file-based asset hash cache is cleared
-                clearCacheSpy.calledOnce.should.be.true();
+                sinon.assert.calledOnce(clearCacheSpy);
 
                 // Check te view cache was cleared
                 assert.deepEqual(fakeBlogApp.cache, {});
@@ -105,7 +105,7 @@ describe('Themes', function () {
                 assert.equal(configStub.calledWith('assetHash', null), true);
 
                 // Check the file-based asset hash cache is cleared
-                clearCacheSpy.calledOnce.should.be.true();
+                sinon.assert.calledOnce(clearCacheSpy);
 
                 // Check te view cache was cleared
                 assert.deepEqual(fakeBlogApp.cache, {});
diff --git a/ghost/core/test/unit/frontend/web/middleware/serve-public-file.test.js b/ghost/core/test/unit/frontend/web/middleware/serve-public-file.test.js
index 97d37bea538..c84e8c88c35 100644
--- a/ghost/core/test/unit/frontend/web/middleware/serve-public-file.test.js
+++ b/ghost/core/test/unit/frontend/web/middleware/serve-public-file.test.js
@@ -23,7 +23,7 @@ describe('servePublicFile', function () {
     it('should return a middleware', function () {
         const result = servePublicFile('static', 'robots.txt', 'text/plain', 3600);
 
-        result.should.be.a.Function();
+        assert.equal(typeof result, 'function');
     });
 
     it('should skip if the request does NOT match the file', function () {
@@ -50,7 +50,7 @@ describe('servePublicFile', function () {
         middleware(req, res, next);
 
         assert.equal(next.called, false);
-        fileStub.firstCall.args[0].should.endWith('core/frontend/public/robots.txt');
+        assert(fileStub.firstCall.args[0].endsWith('core/frontend/public/robots.txt'));
         assert.equal(res.writeHead.called, true);
         assert.equal(res.writeHead.args[0][0], 200);
         assert.equal(res.writeHead.calledWith(200, sinon.match.has('Content-Type')), true);
@@ -80,7 +80,7 @@ describe('servePublicFile', function () {
 
         // File only gets read onece
         assert.equal(fileStub.calledOnce, true);
-        fileStub.firstCall.args[0].should.endWith('core/frontend/public/robots.txt');
+        assert(fileStub.firstCall.args[0].endsWith('core/frontend/public/robots.txt'));
 
         // File gets served twice
         assert.equal(res.writeHead.calledTwice, true);
@@ -116,8 +116,8 @@ describe('servePublicFile', function () {
         assert.equal(fileStub.calledTwice, true);
 
         assert.equal(next.called, false);
-        fileStub.firstCall.args[0].should.endWith('core/frontend/public/robots.txt');
-        fileStub.secondCall.args[0].should.endWith('core/frontend/public/robots.txt');
+        assert(fileStub.firstCall.args[0].endsWith('core/frontend/public/robots.txt'));
+        assert(fileStub.secondCall.args[0].endsWith('core/frontend/public/robots.txt'));
 
         assert.equal(res.writeHead.calledThrice, true);
         assert.equal(res.writeHead.args[0][0], 200);
@@ -189,6 +189,6 @@ describe('servePublicFile', function () {
         assert.equal(res.writeHead.called, true);
         assert.equal(res.writeHead.args[0][0], 200);
 
-        fileStub.firstCall.args[0].should.endWith('/public/something.css');
+        assert(fileStub.firstCall.args[0].endsWith('/public/something.css'));
     });
 });
diff --git a/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js b/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js
index ecc8b2455bd..06ab65bf1ef 100644
--- a/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js
+++ b/ghost/core/test/unit/server/lib/image/cached-image-size-from-url.test.js
@@ -41,7 +41,7 @@ describe('lib/image: image size cache', function () {
         // first call to get result from `getImageSizeFromUrl`
 
         assertExists(cacheStore);
-        cacheStore.get(url).should.not.be.undefined;
+        assertExists(cacheStore.get(url));
         const image = cacheStore.get(url);
         assertExists(image.width);
         assert.equal(image.width, 50);
@@ -54,7 +54,7 @@ describe('lib/image: image size cache', function () {
         assert.equal(imageSizeSpy.calledOnce, true);
         assert.equal(imageSizeSpy.calledTwice, false);
 
-        cacheStore.get(url).should.not.be.undefined;
+        assertExists(cacheStore.get(url));
         const image2 = cacheStore.get(url);
         assertExists(image2.width);
         assert.equal(image2.width, 50);
@@ -108,7 +108,7 @@ describe('lib/image: image size cache', function () {
         assert.equal(result, null);
 
         // Verify 404 was cached with notFound marker
-        cacheStore.get(url).should.not.be.undefined;
+        assertExists(cacheStore.get(url));
         const image = cacheStore.get(url);
         assert.equal(image.url, url);
         assert.equal(image.notFound, true);
diff --git a/ghost/core/test/unit/server/models/base/bulk-filters.test.js b/ghost/core/test/unit/server/models/base/bulk-filters.test.js
index 50a4a5b6707..3c6c1ef9575 100644
--- a/ghost/core/test/unit/server/models/base/bulk-filters.test.js
+++ b/ghost/core/test/unit/server/models/base/bulk-filters.test.js
@@ -14,7 +14,7 @@ describe('Models: bulk-filters', function () {
             const results = [...strategy];
 
             assert.equal(results.length, 1);
-            results[0].should.be.a.Function();
+            assert.equal(typeof results[0], 'function');
         });
     });
 
diff --git a/ghost/core/test/unit/server/models/base/index.test.js b/ghost/core/test/unit/server/models/base/index.test.js
index fdfad2680e8..11ef6c30d4c 100644
--- a/ghost/core/test/unit/server/models/base/index.test.js
+++ b/ghost/core/test/unit/server/models/base/index.test.js
@@ -160,23 +160,23 @@ describe('Models: base', function () {
         it('expect date transformation', function () {
             const data = testUtils.DataGenerator.forKnex.createPost({updated_at: '2018-04-01 07:53:07'});
 
-            data.updated_at.should.be.a.String();
+            assert.equal(typeof data.updated_at, 'string');
 
             models.Base.Model.sanitizeData
                 .bind({prototype: {tableName: 'posts'}})(data);
 
-            data.updated_at.should.be.a.Date();
+            assert(data.updated_at instanceof Date);
         });
 
         it('date is JS date, ignore', function () {
             const data = testUtils.DataGenerator.forKnex.createPost({updated_at: new Date()});
 
-            data.updated_at.should.be.a.Date();
+            assert(data.updated_at instanceof Date);
 
             models.Base.Model.sanitizeData
                 .bind({prototype: {tableName: 'posts'}})(data);
 
-            data.updated_at.should.be.a.Date();
+            assert(data.updated_at instanceof Date);
         });
 
         it('expect date transformation for nested relations', function () {
@@ -187,7 +187,7 @@ describe('Models: base', function () {
                 }]
             });
 
-            data.authors[0].updated_at.should.be.a.String();
+            assert.equal(typeof data.authors[0].updated_at, 'string');
 
             models.Base.Model.sanitizeData
                 .bind({
@@ -199,7 +199,7 @@ describe('Models: base', function () {
                 })(data);
 
             assert.equal(data.authors[0].name, 'Thomas');
-            data.authors[0].updated_at.should.be.a.Date();
+            assert(data.authors[0].updated_at instanceof Date);
         });
     });
 
diff --git a/ghost/core/test/unit/server/models/user.test.js b/ghost/core/test/unit/server/models/user.test.js
index 79111f98da5..57137d86f3e 100644
--- a/ghost/core/test/unit/server/models/user.test.js
+++ b/ghost/core/test/unit/server/models/user.test.js
@@ -496,8 +496,7 @@ describe('Unit: models/user', function () {
                 .then(Promise.reject)
                 .catch((err) => {
                     assert(err instanceof errors.ValidationError);
-                    err.message.indexOf('Only administrators can')
-                        .should.be.aboveOrEqual(0, 'contains correct error message');
+                    assert(err.message.includes('Only administrators can'), 'contains correct error message');
                 });
         });
 
@@ -527,8 +526,7 @@ describe('Unit: models/user', function () {
                 .then(Promise.reject)
                 .catch((err) => {
                     assert(err instanceof errors.ValidationError);
-                    err.message.indexOf('Only active administrators can')
-                        .should.be.aboveOrEqual(0, 'contains correct error message');
+                    assert(err.message.includes('Only active administrators can'), 'contains correct error message');
                 });
         });
 
diff --git a/ghost/core/test/unit/server/services/email-analytics/email-analytics-service.test.js b/ghost/core/test/unit/server/services/email-analytics/email-analytics-service.test.js
index 8c578e6f804..501d5f41680 100644
--- a/ghost/core/test/unit/server/services/email-analytics/email-analytics-service.test.js
+++ b/ghost/core/test/unit/server/services/email-analytics/email-analytics-service.test.js
@@ -870,8 +870,8 @@ describe('EmailAnalyticsService', function () {
 
             await service.aggregateEmailStats('memberId');
 
-            assert.equal(service.queries.aggregateEmailStats.calledOnce, true);
-            service.queries.aggregateEmailStats.calledWith('memberId').should.be.true;
+            sinon.assert.calledOnce(service.queries.aggregateEmailStats);
+            sinon.assert.calledWith(service.queries.aggregateEmailStats, 'memberId');
         });
     });
 
@@ -886,8 +886,8 @@ describe('EmailAnalyticsService', function () {
 
             await service.aggregateMemberStats('memberId');
 
-            assert.equal(service.queries.aggregateMemberStats.calledOnce, true);
-            service.queries.aggregateMemberStats.calledWith('memberId').should.be.true;
+            sinon.assert.calledOnce(service.queries.aggregateMemberStats);
+            sinon.assert.calledWith(service.queries.aggregateMemberStats, 'memberId');
         });
     });
 });
diff --git a/ghost/core/test/unit/server/services/mail/ghost-mailer.test.js b/ghost/core/test/unit/server/services/mail/ghost-mailer.test.js
index e0964aaa3a1..164871b0cc8 100644
--- a/ghost/core/test/unit/server/services/mail/ghost-mailer.test.js
+++ b/ghost/core/test/unit/server/services/mail/ghost-mailer.test.js
@@ -67,7 +67,7 @@ describe('Mail: Ghostmailer', function () {
 
         assert('transport' in mailer);
         assert.equal(mailer.transport.transporter.name, 'SMTP');
-        mailer.transport.sendMail.should.be.a.Function();
+        assert.equal(typeof mailer.transport.sendMail, 'function');
     });
 
     it('should fallback to direct if config is empty', function () {
diff --git a/ghost/core/test/unit/server/services/member-welcome-emails/member-welcome-email-renderer.test.js b/ghost/core/test/unit/server/services/member-welcome-emails/member-welcome-email-renderer.test.js
index fe2ec3961f2..69af044962c 100644
--- a/ghost/core/test/unit/server/services/member-welcome-emails/member-welcome-email-renderer.test.js
+++ b/ghost/core/test/unit/server/services/member-welcome-emails/member-welcome-email-renderer.test.js
@@ -240,7 +240,7 @@ describe('MemberWelcomeEmailRenderer', function () {
                 siteSettings: defaultSiteSettings
             });
 
-            result.text.should.be.a.String();
+            assert.equal(typeof result.text, 'string');
             assert(result.text.includes('Hello World'));
         });
 
diff --git a/ghost/core/test/unit/server/services/members/importer/members-csv-importer-stripe-utils.test.js b/ghost/core/test/unit/server/services/members/importer/members-csv-importer-stripe-utils.test.js
index 54923bd18bd..d665b2b9516 100644
--- a/ghost/core/test/unit/server/services/members/importer/members-csv-importer-stripe-utils.test.js
+++ b/ghost/core/test/unit/server/services/members/importer/members-csv-importer-stripe-utils.test.js
@@ -1,7 +1,6 @@
 const assert = require('node:assert/strict');
 require('should');
 const sinon = require('sinon');
-const {DataImportError} = require('@tryghost/errors');
 const MembersCSVImporterStripeUtils = require('../../../../../../core/server/services/members/importer/members-csv-importer-stripe-utils');
 
 describe('MembersCSVImporterStripeUtils', function () {
@@ -130,9 +129,12 @@ describe('MembersCSVImporterStripeUtils', function () {
                 stripeAPIService: stripeAPIServiceStub
             });
 
-            await membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({}, OPTIONS).should.be.rejectedWith(
-                DataImportError,
-                {message: 'Cannot force subscription to product without a Stripe Connection'}
+            await assert.rejects(
+                membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({}, OPTIONS),
+                {
+                    name: 'DataImportError',
+                    message: 'Cannot force subscription to product without a Stripe Connection'
+                }
             );
         });
 
@@ -142,11 +144,12 @@ describe('MembersCSVImporterStripeUtils', function () {
                 stripeAPIService: stripeAPIServiceStub
             });
 
-            await membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({
-                customer_id: CUSTOMER_ID
-            }, OPTIONS).should.be.rejectedWith(
-                DataImportError,
-                {message: 'Cannot find Stripe customer to update subscription'}
+            await assert.rejects(
+                membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({customer_id: CUSTOMER_ID}, OPTIONS),
+                {
+                    name: 'DataImportError',
+                    message: 'Cannot find Stripe customer to update subscription'
+                }
             );
         });
 
@@ -159,11 +162,12 @@ describe('MembersCSVImporterStripeUtils', function () {
                 stripeAPIService: stripeAPIServiceStub
             });
 
-            await membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({
-                customer_id: CUSTOMER_ID
-            }, OPTIONS).should.be.rejectedWith(
-                DataImportError,
-                {message: 'Cannot update subscription when customer does not have an existing subscription'}
+            await assert.rejects(
+                membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({customer_id: CUSTOMER_ID}, OPTIONS),
+                {
+                    name: 'DataImportError',
+                    message: 'Cannot update subscription when customer does not have an existing subscription'
+                }
             );
         });
 
@@ -191,11 +195,12 @@ describe('MembersCSVImporterStripeUtils', function () {
                 stripeAPIService: stripeAPIServiceStub
             });
 
-            await membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({
-                customer_id: CUSTOMER_ID
-            }, OPTIONS).should.be.rejectedWith(
-                DataImportError,
-                {message: 'Cannot update subscription when customer has multiple subscriptions'}
+            await assert.rejects(
+                membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({customer_id: CUSTOMER_ID}, OPTIONS),
+                {
+                    name: 'DataImportError',
+                    message: 'Cannot update subscription when customer has multiple subscriptions'
+                }
             );
         });
 
@@ -216,11 +221,12 @@ describe('MembersCSVImporterStripeUtils', function () {
                 stripeAPIService: stripeAPIServiceStub
             });
 
-            await membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({
-                customer_id: CUSTOMER_ID
-            }, OPTIONS).should.be.rejectedWith(
-                DataImportError,
-                {message: 'Cannot update subscription when existing subscription has multiple items'}
+            await assert.rejects(
+                membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({customer_id: CUSTOMER_ID}, OPTIONS),
+                {
+                    name: 'DataImportError',
+                    message: 'Cannot update subscription when existing subscription has multiple items'
+                }
             );
         });
 
@@ -233,11 +239,12 @@ describe('MembersCSVImporterStripeUtils', function () {
                 stripeAPIService: stripeAPIServiceStub
             });
 
-            await membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({
-                customer_id: CUSTOMER_ID
-            }, OPTIONS).should.be.rejectedWith(
-                DataImportError,
-                {message: 'Cannot update subscription when existing subscription is not recurring'}
+            await assert.rejects(
+                membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({customer_id: CUSTOMER_ID}, OPTIONS),
+                {
+                    name: 'DataImportError',
+                    message: 'Cannot update subscription when existing subscription is not recurring'
+                }
             );
         });
 
@@ -257,12 +264,15 @@ describe('MembersCSVImporterStripeUtils', function () {
                 productRepository: productRepositoryStub
             });
 
-            await membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({
-                customer_id: CUSTOMER_ID,
-                product_id: PRODUCT_ID
-            }, OPTIONS).should.be.rejectedWith(
-                DataImportError,
-                {message: `Cannot find Product ${PRODUCT_ID}`}
+            await assert.rejects(
+                membersCSVImporterStripeUtils.forceStripeSubscriptionToProduct({
+                    customer_id: CUSTOMER_ID,
+                    product_id: PRODUCT_ID
+                }, OPTIONS),
+                {
+                    name: 'DataImportError',
+                    message: `Cannot find Product ${PRODUCT_ID}`
+                }
             );
         });
 
diff --git a/ghost/core/test/unit/server/services/members/members-api/repositories/member-repository.test.js b/ghost/core/test/unit/server/services/members/members-api/repositories/member-repository.test.js
index 28d15c5aa2f..ed4672efe6e 100644
--- a/ghost/core/test/unit/server/services/members/members-api/repositories/member-repository.test.js
+++ b/ghost/core/test/unit/server/services/members/members-api/repositories/member-repository.test.js
@@ -886,7 +886,7 @@ describe('MemberRepository', function () {
                 context: {}
             });
 
-            StripeCustomerSubscription.add.calledOnce.should.be.true();
+            sinon.assert.calledOnce(StripeCustomerSubscription.add);
             const addedData = StripeCustomerSubscription.add.firstCall.args[0];
             assert.equal(addedData.default_payment_card_last4, '8888');
         });
@@ -927,7 +927,7 @@ describe('MemberRepository', function () {
                 context: {}
             });
 
-            StripeCustomerSubscription.add.calledOnce.should.be.true();
+            sinon.assert.calledOnce(StripeCustomerSubscription.add);
             const addedData = StripeCustomerSubscription.add.firstCall.args[0];
             assert.equal(addedData.default_payment_card_last4, null);
         });
@@ -968,7 +968,7 @@ describe('MemberRepository', function () {
                 context: {}
             });
 
-            StripeCustomerSubscription.add.calledOnce.should.be.true();
+            sinon.assert.calledOnce(StripeCustomerSubscription.add);
             const addedData = StripeCustomerSubscription.add.firstCall.args[0];
             assert.equal(addedData.default_payment_card_last4, '4242');
         });
@@ -1017,7 +1017,7 @@ describe('MemberRepository', function () {
                 context: {}
             });
 
-            StripeCustomerSubscription.add.calledOnce.should.be.true();
+            sinon.assert.calledOnce(StripeCustomerSubscription.add);
             const addedData = StripeCustomerSubscription.add.firstCall.args[0];
             assert.equal(addedData.default_payment_card_last4, '1234');
         });
diff --git a/ghost/core/test/unit/server/services/members/request-integrity-token-provider.test.js b/ghost/core/test/unit/server/services/members/request-integrity-token-provider.test.js
index 8ba024cd4bb..d5d3f4f4820 100644
--- a/ghost/core/test/unit/server/services/members/request-integrity-token-provider.test.js
+++ b/ghost/core/test/unit/server/services/members/request-integrity-token-provider.test.js
@@ -22,7 +22,7 @@ describe('RequestIntegrityTokenProvider', function () {
         it('should create a HMAC digest from the secret', function () {
             const token = tokenProvider.create();
 
-            token.should.be.a.String();
+            assert.equal(typeof token, 'string');
             assert(Array.isArray(token.split(':')));
             assert.equal(token.split(':').length, 3);
             const [timestamp, nonce, digest] = token.split(':');
@@ -31,7 +31,8 @@ describe('RequestIntegrityTokenProvider', function () {
 
             assert.match(nonce, /[0-9a-f]{16}/);
 
-            digest.should.be.a.String().with.lengthOf(64);
+            assert.equal(typeof digest, 'string');
+            assert.equal(digest.length, 64);
         });
     });
 
diff --git a/ghost/core/test/unit/server/services/permissions/can-this.test.js b/ghost/core/test/unit/server/services/permissions/can-this.test.js
index 3e6c2eee015..ba7a49566b4 100644
--- a/ghost/core/test/unit/server/services/permissions/can-this.test.js
+++ b/ghost/core/test/unit/server/services/permissions/can-this.test.js
@@ -82,22 +82,22 @@ describe('Permissions', function () {
             const canThisResult = permissions.canThis();
 
             assert(_.isPlainObject(canThisResult.browse));
-            canThisResult.browse.post.should.be.a.Function();
+            assert.equal(typeof canThisResult.browse.post, 'function');
 
             assert(_.isPlainObject(canThisResult.edit));
-            canThisResult.edit.post.should.be.a.Function();
-            canThisResult.edit.tag.should.be.a.Function();
-            canThisResult.edit.user.should.be.a.Function();
-            canThisResult.edit.page.should.be.a.Function();
+            assert.equal(typeof canThisResult.edit.post, 'function');
+            assert.equal(typeof canThisResult.edit.tag, 'function');
+            assert.equal(typeof canThisResult.edit.user, 'function');
+            assert.equal(typeof canThisResult.edit.page, 'function');
 
             assert(_.isPlainObject(canThisResult.add));
-            canThisResult.add.post.should.be.a.Function();
-            canThisResult.add.user.should.be.a.Function();
-            canThisResult.add.page.should.be.a.Function();
+            assert.equal(typeof canThisResult.add.post, 'function');
+            assert.equal(typeof canThisResult.add.user, 'function');
+            assert.equal(typeof canThisResult.add.page, 'function');
 
             assert(_.isPlainObject(canThisResult.destroy));
-            canThisResult.destroy.post.should.be.a.Function();
-            canThisResult.destroy.user.should.be.a.Function();
+            assert.equal(typeof canThisResult.destroy.post, 'function');
+            assert.equal(typeof canThisResult.destroy.user, 'function');
         });
 
         describe('Non user permissions', function () {
diff --git a/ghost/core/test/unit/server/services/permissions/index.test.js b/ghost/core/test/unit/server/services/permissions/index.test.js
index 75be101bea0..72c4ef8524d 100644
--- a/ghost/core/test/unit/server/services/permissions/index.test.js
+++ b/ghost/core/test/unit/server/services/permissions/index.test.js
@@ -80,7 +80,7 @@ describe('Permissions', function () {
             permissions.init().then(function (actions) {
                 assertExists(actions);
 
-                permissions.canThis.should.not.throwError();
+                assert.doesNotThrow(permissions.canThis);
 
                 assert.deepEqual(_.keys(actions), ['browse', 'edit', 'add', 'destroy']);
 
@@ -99,7 +99,7 @@ describe('Permissions', function () {
             permissions.init().then(function (actions) {
                 assertExists(actions);
 
-                permissions.canThis.should.not.throwError();
+                assert.doesNotThrow(permissions.canThis);
 
                 assert.deepEqual(_.keys(actions), ['browse', 'edit', 'add', 'destroy']);
 
diff --git a/ghost/core/test/unit/server/web/api/middleware/upload.test.js b/ghost/core/test/unit/server/web/api/middleware/upload.test.js
index 41fab41305e..e736201ff99 100644
--- a/ghost/core/test/unit/server/web/api/middleware/upload.test.js
+++ b/ghost/core/test/unit/server/web/api/middleware/upload.test.js
@@ -8,7 +8,7 @@ const assert = require('node:assert/strict');
 describe('web utils', function () {
     describe('checkFileExists', function () {
         it('should return true if file exists in input', function () {
-            validation.checkFileExists({mimetype: 'file', path: 'path'}).should.be.true;
+            assert.equal(validation.checkFileExists({mimetype: 'file', path: 'path'}), true);
         });
 
         it('should return false if file does not exist in input', function () {
@@ -22,17 +22,17 @@ describe('web utils', function () {
 
     describe('checkFileIsValid', function () {
         it('returns true if file has valid extension and type', function () {
-            validation.checkFileIsValid({
+            assert.equal(validation.checkFileIsValid({
                 name: 'test.txt',
                 mimetype: 'text',
                 ext: '.txt'
-            }, ['text'], ['.txt']).should.be.true;
+            }, ['text'], ['.txt']), true);
 
-            validation.checkFileIsValid({
+            assert.equal(validation.checkFileIsValid({
                 name: 'test.jpg',
                 mimetype: 'jpeg',
                 ext: '.jpg'
-            }, ['text', 'jpeg'], ['.txt', '.jpg']).should.be.true;
+            }, ['text', 'jpeg'], ['.txt', '.jpg']), true);
         });
 
         it('returns false if file has invalid extension', function () {
diff --git a/ghost/core/test/unit/shared/custom-theme-settings-cache/cache.test.js b/ghost/core/test/unit/shared/custom-theme-settings-cache/cache.test.js
index 9de73285b39..71bda969dbe 100644
--- a/ghost/core/test/unit/shared/custom-theme-settings-cache/cache.test.js
+++ b/ghost/core/test/unit/shared/custom-theme-settings-cache/cache.test.js
@@ -1,5 +1,4 @@
 const assert = require('node:assert/strict');
-const should = require('should');
 
 const Cache = require('../../../../core/shared/custom-theme-settings-cache/custom-theme-settings-cache');
 
@@ -16,7 +15,6 @@ describe('Cache', function () {
 
             const getAll = cache.getAll();
 
-            getAll.should.have.size(2);
             assert.deepEqual(getAll, {
                 one: 1,
                 two: 2
@@ -43,8 +41,6 @@ describe('Cache', function () {
 
             const getAll = cache.getAll();
 
-            getAll.should.have.size(1);
-            getAll.should.not.have.keys('one', 'two');
             assert.deepEqual(getAll, {
                 three: 3
             });
@@ -108,7 +104,6 @@ describe('Cache', function () {
 
             const returned = cache.getAll();
 
-            returned.should.have.size(2);
             assert.deepEqual(returned, {
                 one: 1,
                 two: 2