diff --git a/docs/eloquent-models/relationships.txt b/docs/eloquent-models/relationships.txt
index 92625f076..2ae716132 100644
--- a/docs/eloquent-models/relationships.txt
+++ b/docs/eloquent-models/relationships.txt
@@ -95,7 +95,7 @@ button to see the data created by running the code:
 
 .. io-code-block::
 
-   .. input:: /includes/eloquent-models/relationships/RelationshipController.php
+   .. input:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
       :language: php
       :dedent:
       :start-after: begin one-to-one save
@@ -125,7 +125,7 @@ button to see the data created by running the code:
 The following sample code shows how to access the related models by using
 the dynamic properties as defined in the example classes:
 
-.. literalinclude:: /includes/eloquent-models/relationships/RelationshipController.php
+.. literalinclude:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
    :language: php
    :dedent:
    :start-after: begin planet orbit dynamic property example
@@ -180,7 +180,7 @@ button to see the data created by running the code:
 
 .. io-code-block::
 
-   .. input:: /includes/eloquent-models/relationships/RelationshipController.php
+   .. input:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
       :language: php
       :dedent:
       :start-after: begin one-to-many save
@@ -219,7 +219,7 @@ button to see the data created by running the code:
 The following sample code shows how to access the related models by using
 the dynamic properties as defined in the example classes.
 
-.. literalinclude:: /includes/eloquent-models/relationships/RelationshipController.php
+.. literalinclude:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
    :language: php
    :dedent:
    :start-after: begin planet moons dynamic property example
@@ -280,7 +280,7 @@ button to see the data created by running the code:
 
 .. io-code-block::
 
-   .. input:: /includes/eloquent-models/relationships/RelationshipController.php
+   .. input:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
       :language: php
       :dedent:
       :start-after: begin many-to-many save
@@ -345,7 +345,7 @@ button to see the data created by running the code:
 The following sample code shows how to access the related models by using
 the dynamic properties as defined in the example classes.
 
-.. literalinclude:: /includes/eloquent-models/relationships/RelationshipController.php
+.. literalinclude:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
    :language: php
    :dedent:
    :start-after: begin many-to-many dynamic property example
@@ -410,7 +410,7 @@ running the code:
 
 .. io-code-block::
 
-   .. input:: /includes/eloquent-models/relationships/RelationshipController.php
+   .. input:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
       :language: php
       :dedent:
       :start-after: begin embedsMany save
@@ -501,7 +501,7 @@ to see the data created by running the code:
 
 .. io-code-block::
 
-   .. input:: /includes/eloquent-models/relationships/RelationshipController.php
+   .. input:: /includes/eloquent-models/relationships/RelationshipsExamplesTest.php
       :language: php
       :dedent:
       :start-after: begin cross-database save
diff --git a/docs/includes/eloquent-models/relationships/RelationshipController.php b/docs/includes/eloquent-models/relationships/RelationshipController.php
deleted file mode 100644
index fc10184d3..000000000
--- a/docs/includes/eloquent-models/relationships/RelationshipController.php
+++ /dev/null
@@ -1,194 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace App\Http\Controllers;
-
-use App\Models\Orbit;
-use App\Models\Planet;
-use Illuminate\Http\Request;
-
-class RelationshipController
-{
-    private function oneToOne()
-    {
-        // begin one-to-one save
-        $planet = new Planet();
-        $planet->name = 'Earth';
-        $planet->diameter_km = 12742;
-        $planet->save();
-
-        $orbit = new Orbit();
-        $orbit->period = 365.26;
-        $orbit->direction = 'counterclockwise';
-
-        $planet->orbit()->save($orbit);
-        // end one-to-one save
-    }
-
-    private function oneToMany()
-    {
-        // begin one-to-many save
-        $planet = new Planet();
-        $planet->name = 'Jupiter';
-        $planet->diameter_km = 142984;
-        $planet->save();
-
-        $moon1 = new Moon();
-        $moon1->name = 'Ganymede';
-        $moon1->orbital_period = 7.15;
-
-        $moon2 = new Moon();
-        $moon2->name = 'Europa';
-        $moon2->orbital_period = 3.55;
-
-        $planet->moons()->save($moon1);
-        $planet->moons()->save($moon2);
-        // end one-to-many save
-    }
-
-    private function planetOrbitDynamic()
-    {
-        // begin planet orbit dynamic property example
-        $planet = Planet::first();
-        $relatedOrbit = $planet->orbit;
-
-        $orbit = Orbit::first();
-        $relatedPlanet = $orbit->planet;
-        // end planet orbit dynamic property example
-    }
-
-    private function planetMoonsDynamic()
-    {
-        // begin planet moons dynamic property example
-        $planet = Planet::first();
-        $relatedMoons = $planet->moons;
-
-        $moon = Moon::first();
-        $relatedPlanet = $moon->planet;
-        // end planet moons dynamic property example
-    }
-
-    private function manyToMany()
-    {
-        // begin many-to-many save
-        $planetEarth = new Planet();
-        $planetEarth->name = 'Earth';
-        $planetEarth->save();
-
-        $planetMars = new Planet();
-        $planetMars->name = 'Mars';
-        $planetMars->save();
-
-        $planetJupiter = new Planet();
-        $planetJupiter->name = 'Jupiter';
-        $planetJupiter->save();
-
-        $explorerTanya = new SpaceExplorer();
-        $explorerTanya->name = 'Tanya Kirbuk';
-        $explorerTanya->save();
-
-        $explorerMark = new SpaceExplorer();
-        $explorerMark->name = 'Mark Watney';
-        $explorerMark->save();
-
-        $explorerJeanluc = new SpaceExplorer();
-        $explorerJeanluc->name = 'Jean-Luc Picard';
-        $explorerJeanluc->save();
-
-        $explorerTanya->planetsVisited()->attach($planetEarth);
-        $explorerTanya->planetsVisited()->attach($planetJupiter);
-        $explorerMark->planetsVisited()->attach($planetEarth);
-        $explorerMark->planetsVisited()->attach($planetMars);
-        $explorerJeanluc->planetsVisited()->attach($planetEarth);
-        $explorerJeanluc->planetsVisited()->attach($planetMars);
-        $explorerJeanluc->planetsVisited()->attach($planetJupiter);
-        // end many-to-many save
-    }
-
-    private function manyToManyDynamic()
-    {
-        // begin many-to-many dynamic property example
-        $planet = Planet::first();
-        $explorers = $planet->visitors;
-
-        $spaceExplorer = SpaceExplorer::first();
-        $explored = $spaceExplorer->planetsVisited;
-        // end many-to-many dynamic property example
-    }
-
-    private function embedsMany()
-    {
-        // begin embedsMany save
-        $spaceship = new SpaceShip();
-        $spaceship->name = 'The Millenium Falcon';
-        $spaceship->save();
-
-        $cargoSpice = new Cargo();
-        $cargoSpice->name = 'spice';
-        $cargoSpice->weight = 50;
-
-        $cargoHyperdrive = new Cargo();
-        $cargoHyperdrive->name = 'hyperdrive';
-        $cargoHyperdrive->weight = 25;
-
-        $spaceship->cargo()->attach($cargoSpice);
-        $spaceship->cargo()->attach($cargoHyperdrive);
-        // end embedsMany save
-    }
-
-    private function crossDatabase()
-    {
-        // begin cross-database save
-        $spaceship = new SpaceShip();
-        $spaceship->id = 1234;
-        $spaceship->name = 'Nostromo';
-        $spaceship->save();
-
-        $passengerEllen = new Passenger();
-        $passengerEllen->name = 'Ellen Ripley';
-
-        $passengerDwayne = new Passenger();
-        $passengerDwayne->name = 'Dwayne Hicks';
-
-        $spaceship->passengers()->save($passengerEllen);
-        $spaceship->passengers()->save($passengerDwayne);
-        // end cross-database save
-    }
-
-    /**
-     * Store a newly created resource in storage.
-     */
-    public function store(Request $request)
-    {
-    }
-
-    /**
-     * Display the specified resource.
-     */
-    public function show()
-    {
-        return 'ok';
-    }
-
-    /**
-     * Show the form for editing the specified resource.
-     */
-    public function edit(Planet $planet)
-    {
-    }
-
-    /**
-     * Update the specified resource in storage.
-     */
-    public function update(Request $request, Planet $planet)
-    {
-    }
-
-    /**
-     * Remove the specified resource from storage.
-     */
-    public function destroy(Planet $planet)
-    {
-    }
-}
diff --git a/docs/includes/eloquent-models/relationships/RelationshipsExamplesTest.php b/docs/includes/eloquent-models/relationships/RelationshipsExamplesTest.php
new file mode 100644
index 000000000..51876416a
--- /dev/null
+++ b/docs/includes/eloquent-models/relationships/RelationshipsExamplesTest.php
@@ -0,0 +1,265 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Http\Controllers;
+
+use App\Models\Cargo;
+use App\Models\Moon;
+use App\Models\Orbit;
+use App\Models\Passenger;
+use App\Models\Planet;
+use App\Models\SpaceExplorer;
+use App\Models\SpaceShip;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Database\Schema\SQLiteBuilder;
+use Illuminate\Support\Facades\Schema;
+use MongoDB\Laravel\Tests\TestCase;
+
+use function assert;
+
+class RelationshipsExamplesTest extends TestCase
+{
+    /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
+     */
+    public function testOneToOne(): void
+    {
+        require_once __DIR__ . '/one-to-one/Orbit.php';
+        require_once __DIR__ . '/one-to-one/Planet.php';
+
+        // Clear the database
+        Planet::truncate();
+        Orbit::truncate();
+
+        // begin one-to-one save
+        $planet = new Planet();
+        $planet->name = 'Earth';
+        $planet->diameter_km = 12742;
+        $planet->save();
+
+        $orbit = new Orbit();
+        $orbit->period = 365.26;
+        $orbit->direction = 'counterclockwise';
+
+        $planet->orbit()->save($orbit);
+        // end one-to-one save
+
+        $planet = Planet::first();
+        $this->assertInstanceOf(Planet::class, $planet);
+        $this->assertInstanceOf(Orbit::class, $planet->orbit);
+
+        // begin planet orbit dynamic property example
+        $planet = Planet::first();
+        $relatedOrbit = $planet->orbit;
+
+        $orbit = Orbit::first();
+        $relatedPlanet = $orbit->planet;
+        // end planet orbit dynamic property example
+
+        $this->assertInstanceOf(Orbit::class, $relatedOrbit);
+        $this->assertInstanceOf(Planet::class, $relatedPlanet);
+    }
+
+    /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
+     */
+    public function testOneToMany(): void
+    {
+        require_once __DIR__ . '/one-to-many/Planet.php';
+        require_once __DIR__ . '/one-to-many/Moon.php';
+
+        // Clear the database
+        Planet::truncate();
+        Moon::truncate();
+
+        // begin one-to-many save
+        $planet = new Planet();
+        $planet->name = 'Jupiter';
+        $planet->diameter_km = 142984;
+        $planet->save();
+
+        $moon1 = new Moon();
+        $moon1->name = 'Ganymede';
+        $moon1->orbital_period = 7.15;
+
+        $moon2 = new Moon();
+        $moon2->name = 'Europa';
+        $moon2->orbital_period = 3.55;
+
+        $planet->moons()->save($moon1);
+        $planet->moons()->save($moon2);
+        // end one-to-many save
+
+        $planet = Planet::first();
+        $this->assertInstanceOf(Planet::class, $planet);
+        $this->assertCount(2, $planet->moons);
+        $this->assertInstanceOf(Moon::class, $planet->moons->first());
+
+        // begin planet moons dynamic property example
+        $planet = Planet::first();
+        $relatedMoons = $planet->moons;
+
+        $moon = Moon::first();
+        $relatedPlanet = $moon->planet;
+        // end planet moons dynamic property example
+
+        $this->assertInstanceOf(Moon::class, $relatedMoons->first());
+        $this->assertInstanceOf(Planet::class, $relatedPlanet);
+    }
+
+    /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
+     */
+    public function testManyToMany(): void
+    {
+        require_once __DIR__ . '/many-to-many/Planet.php';
+        require_once __DIR__ . '/many-to-many/SpaceExplorer.php';
+
+        // Clear the database
+        Planet::truncate();
+        SpaceExplorer::truncate();
+
+        // begin many-to-many save
+        $planetEarth = new Planet();
+        $planetEarth->name = 'Earth';
+        $planetEarth->save();
+
+        $planetMars = new Planet();
+        $planetMars->name = 'Mars';
+        $planetMars->save();
+
+        $planetJupiter = new Planet();
+        $planetJupiter->name = 'Jupiter';
+        $planetJupiter->save();
+
+        $explorerTanya = new SpaceExplorer();
+        $explorerTanya->name = 'Tanya Kirbuk';
+        $explorerTanya->save();
+
+        $explorerMark = new SpaceExplorer();
+        $explorerMark->name = 'Mark Watney';
+        $explorerMark->save();
+
+        $explorerJeanluc = new SpaceExplorer();
+        $explorerJeanluc->name = 'Jean-Luc Picard';
+        $explorerJeanluc->save();
+
+        $explorerTanya->planetsVisited()->attach($planetEarth);
+        $explorerTanya->planetsVisited()->attach($planetJupiter);
+        $explorerMark->planetsVisited()->attach($planetEarth);
+        $explorerMark->planetsVisited()->attach($planetMars);
+        $explorerJeanluc->planetsVisited()->attach($planetEarth);
+        $explorerJeanluc->planetsVisited()->attach($planetMars);
+        $explorerJeanluc->planetsVisited()->attach($planetJupiter);
+        // end many-to-many save
+
+        $planet = Planet::where('name', 'Earth')->first();
+        $this->assertInstanceOf(Planet::class, $planet);
+        $this->assertCount(3, $planet->visitors);
+        $this->assertInstanceOf(SpaceExplorer::class, $planet->visitors->first());
+
+        $explorer = SpaceExplorer::where('name', 'Jean-Luc Picard')->first();
+        $this->assertInstanceOf(SpaceExplorer::class, $explorer);
+        $this->assertCount(3, $explorer->planetsVisited);
+        $this->assertInstanceOf(Planet::class, $explorer->planetsVisited->first());
+
+        // begin many-to-many dynamic property example
+        $planet = Planet::first();
+        $explorers = $planet->visitors;
+
+        $spaceExplorer = SpaceExplorer::first();
+        $explored = $spaceExplorer->planetsVisited;
+        // end many-to-many dynamic property example
+
+        $this->assertCount(3, $explorers);
+        $this->assertInstanceOf(SpaceExplorer::class, $explorers->first());
+        $this->assertCount(2, $explored);
+        $this->assertInstanceOf(Planet::class, $explored->first());
+    }
+
+    /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
+     */
+    public function testEmbedsMany(): void
+    {
+        require_once __DIR__ . '/embeds/Cargo.php';
+        require_once __DIR__ . '/embeds/SpaceShip.php';
+
+        // Clear the database
+        SpaceShip::truncate();
+
+        // begin embedsMany save
+        $spaceship = new SpaceShip();
+        $spaceship->name = 'The Millenium Falcon';
+        $spaceship->save();
+
+        $cargoSpice = new Cargo();
+        $cargoSpice->name = 'spice';
+        $cargoSpice->weight = 50;
+
+        $cargoHyperdrive = new Cargo();
+        $cargoHyperdrive->name = 'hyperdrive';
+        $cargoHyperdrive->weight = 25;
+
+        $spaceship->cargo()->attach($cargoSpice);
+        $spaceship->cargo()->attach($cargoHyperdrive);
+        // end embedsMany save
+
+        $spaceship = SpaceShip::first();
+        $this->assertInstanceOf(SpaceShip::class, $spaceship);
+        $this->assertCount(2, $spaceship->cargo);
+        $this->assertInstanceOf(Cargo::class, $spaceship->cargo->first());
+    }
+
+    /**
+     * @runInSeparateProcess
+     * @preserveGlobalState disabled
+     */
+    public function testCrossDatabase(): void
+    {
+        require_once __DIR__ . '/cross-db/Passenger.php';
+        require_once __DIR__ . '/cross-db/SpaceShip.php';
+
+        $schema = Schema::connection('sqlite');
+        assert($schema instanceof SQLiteBuilder);
+
+        $schema->dropIfExists('space_ships');
+        $schema->create('space_ships', function (Blueprint $table) {
+            $table->id();
+            $table->string('name');
+            $table->timestamps();
+        });
+
+        // Clear the database
+        Passenger::truncate();
+
+        // begin cross-database save
+        $spaceship = new SpaceShip();
+        $spaceship->id = 1234;
+        $spaceship->name = 'Nostromo';
+        $spaceship->save();
+
+        $passengerEllen = new Passenger();
+        $passengerEllen->name = 'Ellen Ripley';
+
+        $passengerDwayne = new Passenger();
+        $passengerDwayne->name = 'Dwayne Hicks';
+
+        $spaceship->passengers()->save($passengerEllen);
+        $spaceship->passengers()->save($passengerDwayne);
+        // end cross-database save
+
+        $spaceship = SpaceShip::first();
+        $this->assertInstanceOf(SpaceShip::class, $spaceship);
+        $this->assertCount(2, $spaceship->passengers);
+        $this->assertInstanceOf(Passenger::class, $spaceship->passengers->first());
+
+        $passenger = Passenger::first();
+        $this->assertInstanceOf(Passenger::class, $passenger);
+    }
+}
diff --git a/docs/includes/eloquent-models/relationships/cross-db/Passenger.php b/docs/includes/eloquent-models/relationships/cross-db/Passenger.php
index 4ceb7c45b..3379c866b 100644
--- a/docs/includes/eloquent-models/relationships/cross-db/Passenger.php
+++ b/docs/includes/eloquent-models/relationships/cross-db/Passenger.php
@@ -4,8 +4,8 @@
 
 namespace App\Models;
 
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use MongoDB\Laravel\Eloquent\Model;
-use MongoDB\Laravel\Relations\BelongsTo;
 
 class Passenger extends Model
 {