diff --git a/tests/newsletter.spec.ts b/tests/newsletter.spec.ts
index bfda19d..36f1c8e 100644
--- a/tests/newsletter.spec.ts
+++ b/tests/newsletter.spec.ts
@@ -72,4 +72,40 @@ test.describe('Newsletter page', () => {
     await expect(duplicate).toContainText('You are already subscribed with this email.');
     await expect(page.getByTestId('newsletter-success')).toHaveCount(0);
   });
+
+  test('should increment the subscriber count on success only and pluralize it correctly', async ({ page }) => {
+    await page.goto('/newsletter');
+
+    const emailField = page.getByTestId('newsletter-email');
+    const subscribe = page.getByTestId('newsletter-subscribe');
+    const count = page.getByTestId('newsletter-count');
+    const firstEmail = uniqueEmail();
+
+    // Fresh load: zero subscribers, pluralized.
+    await expect(count).toHaveText('0 subscribers');
+
+    // A valid subscription increments the count to 1 (singular wording).
+    await emailField.fill(firstEmail);
+    await subscribe.click();
+    await expect(page.getByTestId('newsletter-success')).toBeVisible();
+    await expect(count).toHaveText('1 subscriber');
+
+    // An invalid email is rejected and must not increment the count.
+    await emailField.fill('not-an-email');
+    await subscribe.click();
+    await expect(page.getByTestId('newsletter-error')).toBeVisible();
+    await expect(count).toHaveText('1 subscriber');
+
+    // A duplicate submission is rejected and must not increment the count.
+    await emailField.fill(firstEmail);
+    await subscribe.click();
+    await expect(page.getByTestId('newsletter-duplicate')).toBeVisible();
+    await expect(count).toHaveText('1 subscriber');
+
+    // A second distinct valid subscription increments to 2 (plural wording restored).
+    await emailField.fill(uniqueEmail());
+    await subscribe.click();
+    await expect(page.getByTestId('newsletter-success')).toBeVisible();
+    await expect(count).toHaveText('2 subscribers');
+  });
 });
diff --git a/tests/specs/test-plan.md b/tests/specs/test-plan.md
index 6940dcb..3968fff 100644
--- a/tests/specs/test-plan.md
+++ b/tests/specs/test-plan.md
@@ -280,6 +280,20 @@ Sample Web App — a React application with React Router that provides routes su
          Expectation: The success message (getByTestId('newsletter-success')) is visible
       2. Step: Without navigating away, fill the email field with the same email again and click Subscribe
          Expectation: The duplicate alert (getByTestId('newsletter-duplicate'), role="alert") is visible with text "You are already subscribed with this email.", and no success message (getByTestId('newsletter-success')) is present
+32. **Newsletter subscriber count increments on success only and pluralizes correctly** — `tests/newsletter.spec.ts`
+    - Preconditions: None — `/newsletter` is a public route; the subscriber count (`#newsletter-count` / getByTestId('newsletter-count')) is derived from the in-memory `subscribed` list in `Newsletter.js`, which resets on navigation. All submissions happen within a single page load (the count and duplicate guard rely on that in-memory list). Nothing to create or clean up.
+    - Postconditions: None — no server-side data is created; the list is discarded on navigation.
+    - Step/Expectation Pairs:
+      1. Step: Navigate to /newsletter and read the subscriber count (getByTestId('newsletter-count')) on a fresh load
+        Expectation: The count reads "0 subscribers" (plural wording at zero)
+      2. Step: Fill the email field (getByTestId('newsletter-email')) with a unique valid email and click Subscribe (getByTestId('newsletter-subscribe'))
+        Expectation: The success message appears and the count updates to "1 subscriber" (singular wording at one)
+      3. Step: Fill the email field with an invalid value (e.g. "not-an-email") and click Subscribe
+        Expectation: The error alert appears and the count still reads "1 subscriber" (a rejected submission must not increment the count)
+      4. Step: Fill the email field with the same email used in step 2 and click Subscribe
+        Expectation: The duplicate alert appears and the count still reads "1 subscriber" (a duplicate submission must not increment the count)
+      5. Step: Fill the email field with a second, different unique valid email and click Subscribe
+        Expectation: The success message appears and the count updates to "2 subscribers" (plural wording restored above one)
 
 ### Home
 23. **Home landing page renders the welcome heading and both call-to-action links** — `tests/home.spec.ts`