Tests: Always start transaction before seeding

tests/integration/TestCase.php

@@ -23,13 +23,6 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase
 {
     use BuildsHttpRequests;
 
-    protected function setUp(): void
-    {
-        parent::setUp();
-
-        $this->database()->beginTransaction();
-    }
-
     protected function tearDown(): void
     {
         parent::tearDown();
@@ -61,6 +54,10 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase
             $site->extendWith($this->extenders);
 
             $this->app = $site->bootApp();
+
+            $this->database()->beginTransaction();
+
+            $this->populateDatabase();
         }
 
         return $this->app;
@@ -103,13 +100,23 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase
         return $this->database;
     }
 
+    protected $databaseContent = [];
+
     protected function prepareDatabase(array $tableData)
+    {
+        $this->databaseContent = array_merge_recursive(
+            $this->databaseContent,
+            $tableData
+        );
+    }
+
+    protected function populateDatabase()
     {
         // We temporarily disable foreign key checks to simplify this process.
         $this->database()->getSchemaBuilder()->disableForeignKeyConstraints();
 
         // Then, insert all rows required for this test case.
-        foreach ($tableData as $table => $rows) {
+        foreach ($this->databaseContent as $table => $rows) {
             foreach ($rows as $row) {
                 if ($table === 'settings') {
                     $this->database()->table($table)->updateOrInsert(