diff --git a/src/db/DittoDB.ts b/src/db/DittoDB.ts
index 68fdc627..fbca18d9 100644
--- a/src/db/DittoDB.ts
+++ b/src/db/DittoDB.ts
@@ -47,7 +47,7 @@ export class DittoDB {
       provider: new FileMigrationProvider({
         fs,
         path,
-        migrationFolder: new URL(import.meta.resolve('../db/migrations')).pathname,
+        migrationFolder: new URL(import.meta.resolve('./migrations')).pathname,
       }),
     });
 
diff --git a/src/test.ts b/src/test.ts
index ea9c8fa4..c2dd5b06 100644
--- a/src/test.ts
+++ b/src/test.ts
@@ -1,6 +1,13 @@
-import { NostrEvent } from '@nostrify/nostrify';
+import fs from 'node:fs/promises';
+import path from 'node:path';
+
+import { Database as Sqlite } from '@db/sqlite';
+import { NDatabase, NostrEvent } from '@nostrify/nostrify';
+import { DenoSqlite3Dialect } from '@soapbox/kysely-deno-sqlite';
+import { FileMigrationProvider, Kysely, Migrator } from 'kysely';
 import { finalizeEvent, generateSecretKey } from 'nostr-tools';
 
+import { DittoTables } from '@/db/DittoTables.ts';
 import { purifyEvent } from '@/storages/hydrate.ts';
 
 /** Import an event fixture by name in tests. */
@@ -21,3 +28,31 @@ export function genEvent(t: Partial<NostrEvent> = {}, sk: Uint8Array = generateS
 
   return purifyEvent(event);
 }
+
+/** Get an in-memory SQLite database to use for testing. It's automatically destroyed when it goes out of scope. */
+export async function getTestDB() {
+  const kysely = new Kysely<DittoTables>({
+    dialect: new DenoSqlite3Dialect({
+      database: new Sqlite(':memory:'),
+    }),
+  });
+
+  const migrator = new Migrator({
+    db: kysely,
+    provider: new FileMigrationProvider({
+      fs,
+      path,
+      migrationFolder: new URL(import.meta.resolve('./db/migrations')).pathname,
+    }),
+  });
+
+  await migrator.migrateToLatest();
+
+  const store = new NDatabase(kysely);
+
+  return {
+    store,
+    kysely,
+    [Symbol.asyncDispose]: () => kysely.destroy(),
+  };
+}
diff --git a/src/utils/stats.test.ts b/src/utils/stats.test.ts
new file mode 100644
index 00000000..2d3eaca9
--- /dev/null
+++ b/src/utils/stats.test.ts
@@ -0,0 +1,144 @@
+import { assertEquals } from '@std/assert';
+import { generateSecretKey, getPublicKey } from 'nostr-tools';
+
+import { genEvent, getTestDB } from '@/test.ts';
+import { getAuthorStats, getEventStats, getFollowDiff, updateStats } from '@/utils/stats.ts';
+
+Deno.test('updateStats with kind 1 increments notes count', async () => {
+  await using db = await getTestDB();
+
+  const sk = generateSecretKey();
+  const pubkey = getPublicKey(sk);
+
+  await updateStats({ ...db, event: genEvent({ kind: 1 }, sk) });
+
+  const stats = await getAuthorStats(db.kysely, pubkey);
+
+  assertEquals(stats!.notes_count, 1);
+});
+
+Deno.test('updateStats with kind 5 decrements notes count', async () => {
+  await using db = await getTestDB();
+
+  const sk = generateSecretKey();
+  const pubkey = getPublicKey(sk);
+
+  const create = genEvent({ kind: 1 }, sk);
+  const remove = genEvent({ kind: 5, tags: [['e', create.id]] }, sk);
+
+  await updateStats({ ...db, event: create });
+  assertEquals((await getAuthorStats(db.kysely, pubkey))!.notes_count, 1);
+  await db.store.event(create);
+
+  await updateStats({ ...db, event: remove });
+  assertEquals((await getAuthorStats(db.kysely, pubkey))!.notes_count, 0);
+  await db.store.event(remove);
+});
+
+Deno.test('updateStats with kind 3 increments followers count', async () => {
+  await using db = await getTestDB();
+
+  await updateStats({ ...db, event: genEvent({ kind: 3, tags: [['p', 'alex']] }) });
+  await updateStats({ ...db, event: genEvent({ kind: 3, tags: [['p', 'alex']] }) });
+  await updateStats({ ...db, event: genEvent({ kind: 3, tags: [['p', 'alex']] }) });
+
+  const stats = await getAuthorStats(db.kysely, 'alex');
+
+  assertEquals(stats!.followers_count, 3);
+});
+
+Deno.test('updateStats with kind 3 decrements followers count', async () => {
+  await using db = await getTestDB();
+
+  const sk = generateSecretKey();
+  const follow = genEvent({ kind: 3, tags: [['p', 'alex']], created_at: 0 }, sk);
+  const remove = genEvent({ kind: 3, tags: [], created_at: 1 }, sk);
+
+  await updateStats({ ...db, event: follow });
+  assertEquals((await getAuthorStats(db.kysely, 'alex'))!.followers_count, 1);
+  await db.store.event(follow);
+
+  await updateStats({ ...db, event: remove });
+  assertEquals((await getAuthorStats(db.kysely, 'alex'))!.followers_count, 0);
+  await db.store.event(remove);
+});
+
+Deno.test('getFollowDiff returns added and removed followers', () => {
+  const prev = genEvent({ tags: [['p', 'alex'], ['p', 'bob']] });
+  const next = genEvent({ tags: [['p', 'alex'], ['p', 'carol']] });
+
+  const { added, removed } = getFollowDiff(next.tags, prev.tags);
+
+  assertEquals(added, new Set(['carol']));
+  assertEquals(removed, new Set(['bob']));
+});
+
+Deno.test('updateStats with kind 6 increments reposts count', async () => {
+  await using db = await getTestDB();
+
+  const note = genEvent({ kind: 1 });
+  await updateStats({ ...db, event: note });
+  await db.store.event(note);
+
+  const repost = genEvent({ kind: 6, tags: [['e', note.id]] });
+  await updateStats({ ...db, event: repost });
+  await db.store.event(repost);
+
+  const stats = await getEventStats(db.kysely, note.id);
+
+  assertEquals(stats!.reposts_count, 1);
+});
+
+Deno.test('updateStats with kind 5 decrements reposts count', async () => {
+  await using db = await getTestDB();
+
+  const note = genEvent({ kind: 1 });
+  await updateStats({ ...db, event: note });
+  await db.store.event(note);
+
+  const sk = generateSecretKey();
+  const repost = genEvent({ kind: 6, tags: [['e', note.id]] }, sk);
+  await updateStats({ ...db, event: repost });
+  await db.store.event(repost);
+
+  await updateStats({ ...db, event: genEvent({ kind: 5, tags: [['e', repost.id]] }, sk) });
+
+  const stats = await getEventStats(db.kysely, note.id);
+
+  assertEquals(stats!.reposts_count, 0);
+});
+
+Deno.test('updateStats with kind 7 increments reactions count', async () => {
+  await using db = await getTestDB();
+
+  const note = genEvent({ kind: 1 });
+  await updateStats({ ...db, event: note });
+  await db.store.event(note);
+
+  const reaction = genEvent({ kind: 7, tags: [['e', note.id]] });
+  await updateStats({ ...db, event: reaction });
+  await db.store.event(reaction);
+
+  const stats = await getEventStats(db.kysely, note.id);
+
+  assertEquals(stats!.reactions_count, 1);
+});
+
+Deno.test('updateStats with kind 5 decrements reactions count', async () => {
+  await using db = await getTestDB();
+
+  const note = genEvent({ kind: 1 });
+  await updateStats({ ...db, event: note });
+  await db.store.event(note);
+
+  const sk = generateSecretKey();
+  const reaction = genEvent({ kind: 7, tags: [['e', note.id]] }, sk);
+  await updateStats({ ...db, event: reaction });
+  await db.store.event(reaction);
+
+  await updateStats({ ...db, event: genEvent({ kind: 5, tags: [['e', reaction.id]] }, sk) });
+
+  const stats = await getEventStats(db.kysely, note.id);
+
+  assertEquals(stats!.reactions_count, 0);
+});
diff --git a/src/utils/stats.ts b/src/utils/stats.ts
index af12a251..306bdabf 100644
--- a/src/utils/stats.ts
+++ b/src/utils/stats.ts
@@ -95,6 +95,18 @@ export function getFollowDiff(
   };
 }
 
+/** Retrieve the author stats by the pubkey. */
+export function getAuthorStats(
+  kysely: Kysely<DittoTables>,
+  pubkey: string,
+): Promise<DittoTables['author_stats'] | undefined> {
+  return kysely
+    .selectFrom('author_stats')
+    .selectAll()
+    .where('pubkey', '=', pubkey)
+    .executeTakeFirst();
+}
+
 /** Retrieve the author stats by the pubkey, then call the callback to update it. */
 export async function updateAuthorStats(
   kysely: Kysely<DittoTables>,
@@ -108,11 +120,7 @@ export async function updateAuthorStats(
     notes_count: 0,
   };
 
-  const prev = await kysely
-    .selectFrom('author_stats')
-    .selectAll()
-    .where('pubkey', '=', pubkey)
-    .executeTakeFirst();
+  const prev = await getAuthorStats(kysely, pubkey);
 
   const stats = fn(prev ?? empty);
 
@@ -128,6 +136,18 @@ export async function updateAuthorStats(
   }
 }
 
+/** Retrieve the event stats by the event ID. */
+export function getEventStats(
+  kysely: Kysely<DittoTables>,
+  eventId: string,
+): Promise<DittoTables['event_stats'] | undefined> {
+  return kysely
+    .selectFrom('event_stats')
+    .selectAll()
+    .where('event_id', '=', eventId)
+    .executeTakeFirst();
+}
+
 /** Retrieve the event stats by the event ID, then call the callback to update it. */
 export async function updateEventStats(
   kysely: Kysely<DittoTables>,
@@ -141,11 +161,7 @@ export async function updateEventStats(
     reactions_count: 0,
   };
 
-  const prev = await kysely
-    .selectFrom('event_stats')
-    .selectAll()
-    .where('event_id', '=', eventId)
-    .executeTakeFirst();
+  const prev = await getEventStats(kysely, eventId);
 
   const stats = fn(prev ?? empty);