Add ServerManagerTest, fix a lot of bugs

tests/ServerManagerTest.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Stancl\Tenancy\Tests;
+
+use Stancl\Tenancy\ServerManager;
+
+class ServerManagerTest extends TestCase
+{
+    public function setUp()
+    {
+        parent::setUp();
+
+        $this->serverManager = app(ServerManager::class);
+    }
+
+    /** @test */
+    public function getConfigFilePath_works_when_single_file_mode_is_used()
+    {
+        config([
+            'tenancy.server.file.single' => true,
+            'tenancy.server.file.path' => '/foo/bar',
+        ]);
+        
+        $this->assertSame('/foo/bar', $this->serverManager->getConfigFilePath());
+    }
+
+    /** @test */
+    public function getConfigFilePath_works_when_multiple_files_mode_is_used()
+    {
+        config([
+            'tenancy.server.file.single' => false,
+            'tenancy.server.file.path' => [
+                'prefix' => '/etc/foo',
+                'suffix' => 'bar'
+            ],
+        ]);
+
+        $uuid = tenant('uuid');
+
+        $this->assertSame("/etc/foo{$uuid}bar", $this->serverManager->getConfigFilePath());
+    }
+}