diff --git a/tests/Services/WikiUserEmailCheckerTest.php b/tests/Services/WikiUserEmailCheckerTest.php
new file mode 100644
index 00000000..759ca38a
--- /dev/null
+++ b/tests/Services/WikiUserEmailCheckerTest.php
@@ -0,0 +1,65 @@
+<?php
+
+namespace Tests;
+
+use App\Services\WikiUserEmailChecker;
+use App\WikiDb;
+use Illuminate\Database\DatabaseManager;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+
+class WikiUserEmailCheckerTest extends TestCase {
+    use RefreshDatabase;
+
+    private DatabaseManager $db;
+
+    private $databases = [
+        ['prefix' => 'db_1', 'name' => 'mwdb_1', 'emails' => ['user1@email.localhost', 'user2@email.localhost']],
+        ['prefix' => 'db_2', 'name' => 'mwdb_2', 'emails' => ['user1@email.localhost']],
+        ['prefix' => 'db_3', 'name' => 'mwdb_3', 'emails' => []],
+    ];
+
+    protected function setUp(): void {
+        parent::setUp();
+        $this->db = $this->app->make('db');
+        $this->deleteDatabases();
+        $pdo = $this->db->connection('mw')->getPdo();
+        foreach ($this->databases as $database) {
+            $pdo->exec("CREATE DATABASE {$database['name']}");
+            $userTable = "{$database['name']}.{$database['prefix']}_user";
+            $pdo->exec("CREATE TABLE {$userTable} (user_email TINYBLOB)");
+            if ($database['emails']) {
+                $users = implode(',', array_map(fn ($email) => "('$email')", $database['emails']));
+                $pdo->exec("INSERT INTO {$userTable} VALUES {$users}");
+            }
+        }
+    }
+
+    protected function tearDown(): void {
+        $this->deleteDatabases();
+        WikiDb::query()->delete();
+        parent::tearDown();
+    }
+
+    private function deleteDatabases(): void {
+        $pdo = $this->db->connection('mw')->getPdo();
+        foreach ($this->databases as $database) {
+            $pdo->exec("DROP DATABASE IF EXISTS {$database['name']};");
+        }
+    }
+
+    public function testCorrectDatabaseFound(): void {
+        $checker = new WikiUserEmailChecker($this->db);
+        $this->assertEquals(
+            ['mwdb_1.db_1_user'],
+            $checker->findEmail('user2@email.localhost')
+        );
+    }
+
+    public function testEmailFoundInMultipleDatabases(): void {
+        $checker = new WikiUserEmailChecker($this->db);
+        $this->assertEquals(
+            ['mwdb_1.db_1_user', 'mwdb_2.db_2_user'],
+            $checker->findEmail('user1@email.localhost')
+        );
+    }
+}