diff --git a/src/app/Sku.php b/src/app/Sku.php
index 083587a0..04d44701 100644
--- a/src/app/Sku.php
+++ b/src/app/Sku.php
@@ -1,57 +1,71 @@
 <?php
 
 namespace App;
 
 use Illuminate\Database\Eloquent\Model;
 use Spatie\Translatable\HasTranslations;
 
 /**
  * The eloquent definition of a Stock Keeping Unit (SKU).
+ *
+ * @property string $id
+ * @property bool $incrementing
+ * @property array $casts
+ * @property array $fillable
+ * @property bool $active
+ * @property int $cost
+ * @property string $description
+ * @property string $handler_class
+ * @property string $name
+ * @property string $period
+ * @property string $title
+ * @property integer $units_free
  */
 class Sku extends Model
 {
     use HasTranslations;
 
     public $incrementing = false;
     protected $keyType = 'string';
 
     protected $casts = [
+        'cost' => 'integer',
         'units_free' => 'integer'
     ];
 
     protected $fillable = [
         'active',
         'cost',
         'description',
         'handler_class',
         'name',
         // persist for annual domain registration
         'period',
         'title',
         'units_free',
     ];
 
     /** @var array Translatable properties */
     public $translatable = [
         'name',
         'description',
     ];
 
     /**
      * List the entitlements that consume this SKU.
      *
      * @return \Illuminate\Database\Eloquent\Relations\HasMany
      */
     public function entitlements()
     {
         return $this->hasMany('App\Entitlement');
     }
 
     public function packages()
     {
         return $this->belongsToMany(
             'App\Package',
             'package_skus'
         )->using('App\PackageSku')->withPivot(['cost', 'qty']);
     }
 }
diff --git a/src/tests/Functional/Methods/PackageSkuTest.php b/src/tests/Functional/Methods/PackageSkuTest.php
new file mode 100644
index 00000000..20174b25
--- /dev/null
+++ b/src/tests/Functional/Methods/PackageSkuTest.php
@@ -0,0 +1,127 @@
+<?php
+
+namespace Tests\Functional\Methods;
+
+use Illuminate\Support\Facades\Queue;
+use Tests\TestCase;
+
+/**
+ * Verify the functioning of \App\PackageSku methods.
+ */
+class PackageSkuTest extends TestCase
+{
+    private $packageKolabTest;
+    private $skuGroupwareTest;
+    private $skuMailboxTest;
+    private $skuStorageTest;
+
+    public function setUp(): void
+    {
+        parent::setUp();
+
+        $skuGroupware = \App\Sku::where('title', 'groupware')->first();
+        $skuGroupwareTestAttributes = $skuGroupware->toArray();
+        $skuGroupwareTestAttributes['title'] = 'groupware-test';
+        $this->skuGroupwareTest = \App\Sku::create($skuGroupwareTestAttributes);
+
+        $skuMailbox = \App\Sku::where('title', 'mailbox')->first();
+        $skuMailboxTestAttributes = $skuMailbox->toArray();
+        $skuMailboxTestAttributes['title'] = 'mailbox-test';
+        $this->skuMailboxTest = \App\Sku::create($skuMailboxTestAttributes);
+
+        $skuStorage = \App\Sku::where('title', 'storage')->first();
+        $skuStorageTestAttributes = $skuStorage->toArray();
+        $skuStorageTestAttributes['title'] = 'storage-test';
+        $this->skuStorageTest = \App\Sku::create($skuStorageTestAttributes);
+
+        $this->packageKolabTest = \App\Package::create(
+            [
+                'title' => 'kolab-test',
+                'description' => 'A test package',
+                'name' => "A Kolab Test Package"
+            ]
+        );
+
+        $this->packageKolabTest->skus()->saveMany(
+            [
+                $this->skuGroupwareTest,
+                $this->skuMailboxTest,
+                $this->skuStorageTest
+            ]
+        );
+
+        $this->packageKolabTest->skus()->updateExistingPivot(
+            $this->skuStorageTest,
+            ['qty' => 2],
+            false
+        );
+    }
+
+    public function tearDown(): void
+    {
+        $this->packageKolabTest->forceDelete();
+        $this->skuGroupwareTest->forceDelete();
+        $this->skuMailboxTest->forceDelete();
+        $this->skuStorageTest->forceDelete();
+
+        parent::tearDown();
+    }
+
+    public function testCostNegativeNetUnits()
+    {
+        foreach ($this->packageKolabTest->skus as $sku) {
+            $sku->units_free = $sku->pivot->qty + 1;
+            $sku->save();
+
+            $this->assertEqual($sku->pivot->cost(), 0);
+
+            $sku->units_free -= 1;
+            $sku->save();
+        }
+    }
+
+    public function testCost()
+    {
+        foreach ($this->packageKolabTest->skus as $sku) {
+            $this->assertEqual($sku->pivot->cost(), $sku->cost * ($sku->pivot->qty - $sku->units_free));
+        }
+    }
+
+    public function testCostWithPackageDiscountRate()
+    {
+        foreach ([15, 30, 50, 100] as $rate) {
+            $this->packageKolabTest->discount_rate = $rate;
+            $this->packageKolabTest->save();
+
+            $multiplier = ((100 - $rate) / 100);
+
+            foreach ($this->packageKolabTest->fresh()->skus as $sku) {
+                $expected = $multiplier * $sku->cost * ($sku->pivot->qty - $sku->units_free);
+
+                $this->assertEqual($sku->pivot->cost(), $expected);
+            }
+        }
+    }
+
+    public function testPackage()
+    {
+        foreach ($this->packageKolabTest->skus as $sku) {
+            $this->assertSame($sku->pivot->package->id, $this->packageKolabTest->id);
+        }
+    }
+
+    public function testQty()
+    {
+        $this->markTestIncomplete();
+    }
+
+    public function testSku()
+    {
+        $this->markTestIncomplete();
+    }
+
+    public function testSkuInactive()
+    {
+        $this->markTestIncomplete();
+    }
+}
diff --git a/src/tests/Functional/Methods/PackageTest.php b/src/tests/Functional/Methods/PackageTest.php
index 69c28a03..a21aca6f 100644
--- a/src/tests/Functional/Methods/PackageTest.php
+++ b/src/tests/Functional/Methods/PackageTest.php
@@ -1,58 +1,109 @@
 <?php
 
 namespace Tests\Functional\Methods;
 
 use Illuminate\Support\Facades\Queue;
 use Tests\TestCase;
 
 /**
- * Verify the functioning of \App\Discount methods where additional infrastructure is required, such as Redis and
- * MariaDB.
+ * Verify the functioning of \App\Package methods.
  */
 class PackageTest extends TestCase
 {
     private $packageDomainHosting;
     private $packageKolab;
     private $packageLite;
 
     private $skuDomainHosting;
     private $skuGroupware;
     private $skuMailbox;
     private $skuStorage;
 
     public function setUp(): void
     {
         parent::setUp();
 
         $this->packageDomainHosting = \App\Package::where('title', 'domain-hosting')->first();
         $this->packageKolab = \App\Package::where('title', 'kolab')->first();
         $this->packageLite = \App\Package::where('title', 'lite')->first();
 
         $this->skuDomainHosting = \App\Sku::where('title', 'domain-hosting')->first();
         $this->skuGroupware = \App\Sku::where('title', 'groupware')->first();
         $this->skuMailbox = \App\Sku::where('title', 'mailbox')->first();
         $this->skuStorage = \App\Sku::where('title', 'storage')->first();
     }
 
     public function testSkusDomainHosting()
     {
         // this is without a package quantity manipulator, just unique SKUs
         $this->assertCount(1, $this->packageDomainHosting->skus);
         $this->assertTrue($this->packageDomainHosting->skus->contains($this->skuDomainHosting));
+        $this->assertFalse($this->packageDomainHosting->skus->contains($this->skuGroupware));
+        $this->assertFalse($this->packageDomainHosting->skus->contains($this->skuMailbox));
+        $this->assertFalse($this->packageDomainHosting->skus->contains($this->skuStorage));
     }
 
     public function testSkusKolab()
     {
         // this is without a package quantity manipulator, just unique SKUs
         $this->assertCount(3, $this->packageKolab->skus);
+        $this->assertFalse($this->packageKolab->skus->contains($this->skuDomainHosting));
         $this->assertTrue($this->packageKolab->skus->contains($this->skuGroupware));
         $this->assertTrue($this->packageKolab->skus->contains($this->skuMailbox));
         $this->assertTrue($this->packageKolab->skus->contains($this->skuStorage));
     }
 
     public function testSkusLite()
     {
         // this is without a package quantity manipulator, just unique SKUs
         $this->assertCount(2, $this->packageLite->skus);
+        $this->assertFalse($this->packageLite->skus->contains($this->skuDomainHosting));
+        $this->assertFalse($this->packageLite->skus->contains($this->skuGroupware));
+        $this->assertTrue($this->packageLite->skus->contains($this->skuMailbox));
+        $this->assertTrue($this->packageLite->skus->contains($this->skuStorage));
+    }
+
+    public function testPackageIsDomainFailure()
+    {
+        $this->assertFalse($this->packageKolab->isDomain());
+        $this->assertFalse($this->packageLite->isDomain());
+    }
+
+    public function testPackageIsDomainSuccess()
+    {
+        $this->assertTrue($this->packageDomainHosting->isDomain());
+    }
+
+    public function testPackageDomainHostingCost()
+    {
+        $this->assertEqual($this->packageDomainHosting->cost(), 0);
+    }
+
+    public function testPackageKolabCost()
+    {
+        $this->assertEqual($this->packageKolab->cost(), 999);
+    }
+
+    public function testPackageLiteCost()
+    {
+        $this->assertEqual($this->packageLite->cost(), 444);
+    }
+
+    public function testPackageCostWithNegativeNetUnits()
+    {
+        $skus = $this->packageLite->skus;
+
+        foreach ($skus as $sku) {
+            if ($sku->title == "storage") {
+                $sku->units_free = $sku->pivot->qty + 1;
+            }
+        }
+
+        $this->assertEqual($this->packageLite->cost(), 444);
+    }
+
+    public function testPackageCostWithDiscountRate()
+    {
+        $this->markTestIncomplete();
     }
 }
diff --git a/src/tests/Functional/Methods/PaymentTest.php b/src/tests/Functional/Methods/PaymentTest.php
new file mode 100644
index 00000000..7a150255
--- /dev/null
+++ b/src/tests/Functional/Methods/PaymentTest.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace Tests\Functional\Methods;
+
+use Illuminate\Support\Facades\Queue;
+use Tests\TestCase;
+
+/**
+ * Verify the functioning of \App\Payment methods.
+ */
+class PaymentTest extends TestCase
+{
+    public function setUp(): void
+    {
+        parent::setUp();
+    }
+
+    public function testWallet()
+    {
+        $this->assertInstanceOf('Illuminate\Database\Eloquent\Relations\BelongsTo', (new \App\Payment())->wallet());
+        $this->assertNull((new \App\Payment())->wallet);
+    }
+}
diff --git a/src/tests/Functional/Methods/SkuTest.php b/src/tests/Functional/Methods/SkuTest.php
new file mode 100644
index 00000000..fb6edcc0
--- /dev/null
+++ b/src/tests/Functional/Methods/SkuTest.php
@@ -0,0 +1,19 @@
+<?php
+
+namespace Tests\Functional\Methods;
+
+use Tests\TestCase;
+
+class SkuTest extends TestCase
+{
+    // not a method, but a property test...
+    public function testSkuHandlerClass()
+    {
+        $skus = \App\Sku::all();
+
+        foreach ($skus as $sku) {
+            $this->assertNotNull($sku->handler_class);
+            $this->assertTrue(method_exists($sku->handler_class, 'preReq'));
+        }
+    }
+}