Unify database testing traits with a new FreshDatabase trait.

This trait is based on work by @adamwathan on a better testing workflow
when interacting with databases. In general, the goal is to have a
single trait that “just works” out of the box regardless of whether you
are using an in-memory SQLite database or a conventional MySQL /
Postgres database when testing. The database will be migrated to make
sure it is up to date and then a transaction will be started to make
any records added during the test temporary. Like the database
transaction trait, the current transaction will be rolled back at the
end of each test.

src/Illuminate/Foundation/Console/stubs/test.stub

@@ -3,9 +3,7 @@
 namespace DummyNamespace;
 
 use Tests\TestCase;
-use Illuminate\Foundation\Testing\WithoutMiddleware;
-use Illuminate\Foundation\Testing\DatabaseMigrations;
-use Illuminate\Foundation\Testing\DatabaseTransactions;
+use Illuminate\Foundation\Testing\FreshDatabase;
 
 class DummyClass extends TestCase
 {

src/Illuminate/Foundation/Testing/FreshDatabase.php

@@ -0,0 +1,100 @@
+<?php
+
+namespace Illuminate\Foundation\Testing;
+
+use Illuminate\Contracts\Console\Kernel;
+
+trait FreshDatabase
+{
+    /**
+     * Indicates if the test database has been migrated.
+     *
+     * @var bool
+     */
+    protected static $migrated = false;
+
+    /**
+     * Define hooks to migrate the database before and after each test.
+     *
+     * @return void
+     */
+    public function refreshDatabase()
+    {
+        $this->usingInMemoryDatabase()
+                        ? $this->refreshInMemoryDatabase()
+                        : $this->refreshTestDatabase();
+    }
+
+    /**
+     * Determine if an in-memory database is being used.
+     *
+     * @return bool
+     */
+    protected function usingInMemoryDatabase()
+    {
+        return config('database.connections')[
+            config('database.default')
+        ]['database'] == ':memory:';
+    }
+
+    /**
+     * Refresh the in-memory database.
+     *
+     * @return void
+     */
+    protected function refreshInMemoryDatabase()
+    {
+        $this->artisan('migrate');
+
+        $this->app[Kernel::class]->setArtisan(null);
+    }
+
+    /**
+     * Refresh a conventional test database.
+     *
+     * @return void
+     */
+    protected function refreshTestDatabase()
+    {
+        if (! static::$migrated) {
+            $this->artisan('migrate:fresh');
+
+            $this->app[Kernel::class]->setArtisan(null);
+
+            static::$migrated = true;
+        }
+
+        $this->beginDatabaseTransaction();
+    }
+
+    /**
+     * Begin a database transaction on the testing database.
+     *
+     * @return void
+     */
+    public function beginDatabaseTransaction()
+    {
+        $database = $this->app->make('db');
+
+        foreach ($this->connectionsToTransact() as $name) {
+            $database->connection($name)->beginTransaction();
+        }
+
+        $this->beforeApplicationDestroyed(function () use ($database) {
+            foreach ($this->connectionsToTransact() as $name) {
+                $database->connection($name)->rollBack();
+            }
+        });
+    }
+
+    /**
+     * The database connections that should have transactions.
+     *
+     * @return array
+     */
+    protected function connectionsToTransact()
+    {
+        return property_exists($this, 'connectionsToTransact')
+                            ? $this->connectionsToTransact : [null];
+    }
+}

src/Illuminate/Foundation/Testing/TestCase.php

@@ -99,6 +99,10 @@ protected function setUpTraits()
     {
         $uses = array_flip(class_uses_recursive(static::class));
 
+        if (isset($uses[FreshDatabase::class])) {
+            $this->refreshDatabase();
+        }
+
         if (isset($uses[DatabaseMigrations::class])) {
             $this->runDatabaseMigrations();
         }