Move app nesting to a test state helper

_config/tests.yml

@@ -8,3 +8,12 @@ SilverStripe\Core\Injector\Injector:
         extensions: %$SilverStripe\Dev\ExtensionTestState
         flushable: %$SilverStripe\Dev\FlushableTestState
         requirements: %$SilverStripe\View\Dev\RequirementsTestState
+---
+Name: kerneltest
+Before: '*'
+---
+SilverStripe\Core\Injector\Injector:
+  SilverStripe\Dev\SapphireTestState:
+    properties:
+      States:
+        kernel: %$SilverStripe\Dev\KernelTestState

src/Core/TestKernel.php

@@ -16,11 +16,14 @@ class TestKernel extends AppKernel
     /**
      * Reset kernel between tests.
      * Note: this avoids resetting services (See TestState for service specific reset)
+     *
+     * @return $this
      */
     public function reset()
     {
         $this->setEnvironment(self::DEV);
         $this->bootPHP();
+        return $this;
     }
 
     protected function bootPHP()

src/Dev/KernelTestState.php

@@ -0,0 +1,93 @@
+<?php
+
+namespace SilverStripe\Dev;
+
+use SilverStripe\Core\Injector\Injector;
+use SilverStripe\Core\Kernel;
+use SilverStripe\Core\TestKernel;
+
+/**
+ * Handles nesting of kernel before / after tests
+ */
+class KernelTestState implements TestState
+{
+    /**
+     * Stack of kernels
+     *
+     * @var TestKernel[]
+     */
+    protected $kernels = [];
+
+    /**
+     * Get active Kernel instance
+     *
+     * @return TestKernel
+     */
+    protected function kernel()
+    {
+        return end($this->kernels);
+    }
+
+    /**
+     * Called on setup
+     *
+     * @param SapphireTest $test
+     */
+    public function setUp(SapphireTest $test)
+    {
+        $this->nest();
+    }
+
+    /**
+     * Called on tear down
+     *
+     * @param SapphireTest $test
+     */
+    public function tearDown(SapphireTest $test)
+    {
+        $this->unnest();
+    }
+
+    /**
+     * Called once on setup
+     *
+     * @param string $class Class being setup
+     */
+    public function setUpOnce($class)
+    {
+        // If first run, get initial kernel
+        if (empty($this->kernels)) {
+            $this->kernels[] = Injector::inst()->get(Kernel::class);
+        }
+
+        $this->nest();
+    }
+
+    /**
+     * Called once on tear down
+     *
+     * @param string $class Class being torn down
+     */
+    public function tearDownOnce($class)
+    {
+        $this->unnest();
+    }
+
+    /**
+     * Nest the current kernel
+     */
+    protected function nest()
+    {
+        // Reset state
+        $this->kernel()->reset();
+        $this->kernels[] = $this->kernel()->nest();
+    }
+
+    protected function unnest()
+    {
+        // Unnest and reset
+        array_pop($this->kernels);
+        $this->kernel()->activate();
+        $this->kernel()->reset();
+    }
+}

src/Dev/SapphireTest.php

@@ -18,7 +18,7 @@ use SilverStripe\Core\Config\Config;
 use SilverStripe\Core\HTTPApplication;
 use SilverStripe\Core\Injector\Injector;
 use SilverStripe\Core\Injector\InjectorLoader;
-use SilverStripe\Core\Kernel;
+use SilverStripe\Core\Manifest\ClassLoader;
 use SilverStripe\Core\TestKernel;
 use SilverStripe\i18n\i18n;
 use SilverStripe\ORM\DataExtension;
@@ -129,23 +129,6 @@ class SapphireTest extends PHPUnit_Framework_TestCase
      */
     protected $backupGlobals = false;
 
-    /**
-     * Test application kernel stace.
-     *
-     * @var TestKernel[]
-     */
-    protected static $kernels = [];
-
-    /**
-     * Get active Kernel instance
-     *
-     * @return TestKernel
-     */
-    protected static function kernel()
-    {
-        return end(static::$kernels);
-    }
-
     /**
      * State management container for SapphireTest
      *
@@ -213,12 +196,6 @@ class SapphireTest extends PHPUnit_Framework_TestCase
      */
     protected function setUp()
     {
-        // Reset state
-        static::kernel()->reset();
-
-        // Nest
-        static::$kernels[] = static::kernel()->nest();
-
         // Call state helpers
         static::$state->setUp($this);
 
@@ -306,12 +283,6 @@ class SapphireTest extends PHPUnit_Framework_TestCase
         // Start tests
         static::start();
 
-        // Reset kernel
-        static::kernel()->reset();
-
-        // Nest kernel
-        static::$kernels[] = static::kernel()->nest();
-
         // Call state helpers
         static::$state->setUpOnce(static::class);
 
@@ -340,13 +311,6 @@ class SapphireTest extends PHPUnit_Framework_TestCase
         // Call state helpers
         static::$state->tearDownOnce(static::class);
 
-        // Unnest
-        array_pop(static::$kernels);
-        static::kernel()->activate();
-
-        // Reset PHP state
-        static::kernel()->reset();
-
         // Reset DB schema
         static::resetDBSchema();
     }
@@ -460,7 +424,7 @@ class SapphireTest extends PHPUnit_Framework_TestCase
      */
     protected function getCurrentAbsolutePath()
     {
-        $filename = static::kernel()->getClassLoader()->getItemPath(static::class);
+        $filename = ClassLoader::inst()->getItemPath(static::class);
         if (!$filename) {
             throw new LogicException("getItemPath returned null for " . static::class);
         }
@@ -505,13 +469,6 @@ class SapphireTest extends PHPUnit_Framework_TestCase
 
         // Call state helpers
         static::$state->tearDown($this);
-
-        // Unnest
-        array_pop(static::$kernels);
-        static::kernel()->activate();
-
-        // Reset state
-        static::kernel()->reset();
     }
 
     public static function assertContains(
@@ -922,8 +879,9 @@ class SapphireTest extends PHPUnit_Framework_TestCase
         if (static::is_running_test()) {
             return;
         }
+
         // Health check
-        if (InjectorLoader::inst()->countManifests() || static::kernel()) {
+        if (InjectorLoader::inst()->countManifests()) {
             throw new LogicException("SapphireTest::start() cannot be called within another application");
         }
         static::set_is_running_test(true);
@@ -934,8 +892,8 @@ class SapphireTest extends PHPUnit_Framework_TestCase
         $request->setSession($session);
 
         // Test application
-        static::$kernels[] = new TestKernel();
-        $app = new HTTPApplication(static::kernel());
+        $kernel = new TestKernel();
+        $app = new HTTPApplication($kernel);
 
         // Custom application
         $app->execute(function () use ($request) {