diff --git a/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AddressTest.php b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AddressTest.php
new file mode 100644
index 000000000..5c00e2954
--- /dev/null
+++ b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AddressTest.php
@@ -0,0 +1,52 @@
+<?php
+declare(strict_types=1);
+
+namespace Inpsyde\PayPalCommerce\ApiClient\Entity;
+
+
+use PHPUnit\Framework\TestCase;
+
+class AddressTest extends TestCase
+{
+
+    public function test() {
+        $testee = new Address(
+            'countryCode',
+            'addressLine1',
+            'addressLine2',
+            'adminArea1',
+            'adminArea2',
+            'postalCode'
+        );
+
+        $this->assertEquals('countryCode', $testee->countryCode());
+        $this->assertEquals('addressLine1', $testee->addressLine1());
+        $this->assertEquals('addressLine2', $testee->addressLine2());
+        $this->assertEquals('adminArea1', $testee->adminArea1());
+        $this->assertEquals('adminArea2', $testee->adminArea2());
+        $this->assertEquals('postalCode', $testee->postalCode());
+    }
+    public function testToArray()
+    {
+        $testee = new Address(
+            'countryCode',
+            'addressLine1',
+            'addressLine2',
+            'adminArea1',
+            'adminArea2',
+            'postalCode'
+        );
+
+        $expected = [
+            'country_code' => 'countryCode',
+            'address_line_1' => 'addressLine1',
+            'address_line_2' => 'addressLine2',
+            'admin_area_1' => 'adminArea1',
+            'admin_area_2' => 'adminArea2',
+            'postal_code' => 'postalCode',
+        ];
+
+        $actual = $testee->toArray();
+        $this->assertEquals($expected, $actual);
+    }
+}
\ No newline at end of file
diff --git a/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AmountBreakdownTest.php b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AmountBreakdownTest.php
new file mode 100644
index 000000000..bc18959ba
--- /dev/null
+++ b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AmountBreakdownTest.php
@@ -0,0 +1,122 @@
+<?php
+declare(strict_types=1);
+
+namespace Inpsyde\PayPalCommerce\ApiClient\Entity;
+
+
+use PHPUnit\Framework\TestCase;
+
+class AmountBreakdownTest extends TestCase
+{
+
+    public function test() {
+        $itemTotal = \Mockery::mock(Money::class);
+        $itemTotal
+            ->expects('toArray')->andReturn(['itemTotal']);
+        $shipping = \Mockery::mock(Money::class);
+        $shipping
+            ->expects('toArray')->andReturn(['shipping']);
+        $taxTotal = \Mockery::mock(Money::class);
+        $taxTotal
+            ->expects('toArray')->andReturn(['taxTotal']);
+        $handling = \Mockery::mock(Money::class);
+        $handling
+            ->expects('toArray')->andReturn(['handling']);
+        $insurance = \Mockery::mock(Money::class);
+        $insurance
+            ->expects('toArray')->andReturn(['insurance']);
+        $shippingDiscount = \Mockery::mock(Money::class);
+        $shippingDiscount
+            ->expects('toArray')->andReturn(['shippingDiscount']);
+        $discount = \Mockery::mock(Money::class);
+        $discount
+            ->expects('toArray')->andReturn(['discount']);
+        $testee = new AmountBreakdown(
+            $itemTotal,
+            $shipping,
+            $taxTotal,
+            $handling,
+            $insurance,
+            $shippingDiscount,
+            $discount
+        );
+
+        $this->assertEquals($itemTotal, $testee->itemTotal());
+        $this->assertEquals($shipping, $testee->shipping());
+        $this->assertEquals($taxTotal, $testee->taxTotal());
+        $this->assertEquals($handling, $testee->handling());
+        $this->assertEquals($insurance, $testee->insurance());
+        $this->assertEquals($shippingDiscount, $testee->shippingDiscount());
+        $this->assertEquals($discount, $testee->discount());
+
+        $expected = [
+            'item_total' => ['itemTotal'],
+            'shipping' => ['shipping'],
+            'tax_total' => ['taxTotal'],
+            'handling' => ['handling'],
+            'insurance' => ['insurance'],
+            'shipping_discount' => ['shippingDiscount'],
+            'discount' => ['discount'],
+        ];
+
+        $this->assertEquals($expected, $testee->toArray());
+    }
+
+    /**
+     * @dataProvider dataDropArrayKeyIfNoValueGiven
+     */
+    public function testDropArrayKeyIfNoValueGiven($keyMissing, $methodName) {
+
+        $itemTotal = \Mockery::mock(Money::class);
+        $itemTotal
+            ->expects('toArray')->andReturn(['itemTotal']);
+        $shipping = \Mockery::mock(Money::class);
+        $shipping
+            ->expects('toArray')->andReturn(['shipping']);
+        $taxTotal = \Mockery::mock(Money::class);
+        $taxTotal
+            ->expects('toArray')->andReturn(['taxTotal']);
+        $handling = \Mockery::mock(Money::class);
+        $handling
+            ->expects('toArray')->andReturn(['handling']);
+        $insurance = \Mockery::mock(Money::class);
+        $insurance
+            ->expects('toArray')->andReturn(['insurance']);
+        $shippingDiscount = \Mockery::mock(Money::class);
+        $shippingDiscount
+            ->expects('toArray')->andReturn(['shippingDiscount']);
+        $discount = \Mockery::mock(Money::class);
+        $discount
+            ->expects('toArray')->andReturn(['discount']);
+
+
+        $items = [
+            'item_total' => $itemTotal,
+            'shipping' => $shipping,
+            'tax_total' => $taxTotal,
+            'handling' => $handling,
+            'insurance' => $insurance,
+            'shipping_discount' => $shippingDiscount,
+            'discount' => $discount,
+        ];
+        $items[$keyMissing] = null;
+
+        $testee = new AmountBreakdown(...array_values($items));
+        $array = $testee->toArray();
+        $result = ! array_key_exists($keyMissing, $array);
+        $this->assertTrue($result);
+        $this->assertNull($testee->{$methodName}(), "$methodName should return null");
+    }
+
+    public function dataDropArrayKeyIfNoValueGiven() : array {
+        return [
+            ['item_total', 'itemTotal'],
+            ['shipping', 'shipping'],
+            ['tax_total', 'taxTotal'],
+            ['handling', 'handling'],
+            ['insurance', 'insurance'],
+            ['shipping_discount', 'shippingDiscount'],
+            ['discount', 'discount'],
+        ];
+    }
+}
\ No newline at end of file
diff --git a/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AmountTest.php b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AmountTest.php
new file mode 100644
index 000000000..306e3336e
--- /dev/null
+++ b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/AmountTest.php
@@ -0,0 +1,52 @@
+<?php
+declare(strict_types=1);
+
+namespace Inpsyde\PayPalCommerce\ApiClient\Entity;
+
+
+use PHPUnit\Framework\TestCase;
+
+class AmountTest extends TestCase
+{
+
+    public function test() {
+        $money = \Mockery::mock(Money::class);
+        $money->expects('currencyCode')->andReturn('currencyCode');
+        $money->expects('value')->andReturn(1.10);
+        $testee = new Amount($money);
+
+        $this->assertEquals('currencyCode', $testee->currencyCode());
+        $this->assertEquals(1.10, $testee->value());
+    }
+    public function testBreakdownIsNull() {
+        $money = \Mockery::mock(Money::class);
+        $money->expects('currencyCode')->andReturn('currencyCode');
+        $money->expects('value')->andReturn(1.10);
+        $testee = new Amount($money);
+
+        $this->assertNull($testee->breakdown());
+
+        $expectedArray = [
+            'currency_code' => 'currencyCode',
+            'value' => 1.10,
+        ];
+        $this->assertEquals($expectedArray, $testee->toArray());
+    }
+    public function testBreakdown() {
+        $money = \Mockery::mock(Money::class);
+        $money->expects('currencyCode')->andReturn('currencyCode');
+        $money->expects('value')->andReturn(1.10);
+        $breakdown = \Mockery::mock(AmountBreakdown::class);
+        $breakdown->expects('toArray')->andReturn([1]);
+        $testee = new Amount($money, $breakdown);
+
+        $this->assertEquals($breakdown, $testee->breakdown());
+
+        $expectedArray = [
+            'currency_code' => 'currencyCode',
+            'value' => 1.10,
+            'breakdown' => [1]
+        ];
+        $this->assertEquals($expectedArray, $testee->toArray());
+    }
+}
\ No newline at end of file
diff --git a/modules.local/ppcp-api-client/tests/PHPUnit/Entity/ItemTest.php b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/ItemTest.php
new file mode 100644
index 000000000..a8e6574c4
--- /dev/null
+++ b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/ItemTest.php
@@ -0,0 +1,82 @@
+<?php
+declare(strict_types=1);
+
+namespace Inpsyde\PayPalCommerce\ApiClient\Entity;
+
+
+use PHPUnit\Framework\TestCase;
+
+class ItemTest extends TestCase
+{
+
+    public function test() {
+        $unitAmount = \Mockery::mock(Money::class);
+        $tax = \Mockery::mock(Money::class);
+        $testee = new Item(
+            'name',
+            $unitAmount,
+            1,
+            'description',
+            $tax,
+            'sku',
+            'PHYSICAL_GOODS'
+        );
+
+        $this->assertEquals('name', $testee->name());
+        $this->assertEquals($unitAmount, $testee->unitAmount());
+        $this->assertEquals(1, $testee->quantity());
+        $this->assertEquals('description', $testee->description());
+        $this->assertEquals($tax, $testee->tax());
+        $this->assertEquals('sku', $testee->sku());
+        $this->assertEquals('PHYSICAL_GOODS', $testee->category());
+    }
+
+    public function testDigitalGoodsCategory() {
+        $unitAmount = \Mockery::mock(Money::class);
+        $tax = \Mockery::mock(Money::class);
+        $testee = new Item(
+            'name',
+            $unitAmount,
+            1,
+            'description',
+            $tax,
+            'sku',
+            'DIGITAL_GOODS'
+        );
+
+        $this->assertEquals('DIGITAL_GOODS', $testee->category());
+    }
+
+    public function testToArray() {
+
+        $unitAmount = \Mockery::mock(Money::class);
+        $unitAmount
+            ->expects('toArray')
+            ->andReturn([1]);
+        $tax = \Mockery::mock(Money::class);
+        $tax
+            ->expects('toArray')
+            ->andReturn([2]);
+        $testee = new Item(
+            'name',
+            $unitAmount,
+            1,
+            'description',
+            $tax,
+            'sku',
+            'PHYSICAL_GOODS'
+        );
+
+        $expected = [
+            'name' => 'name',
+            'unit_amount' => [1],
+            'quantity' => 1,
+            'description' => 'description',
+            'sku' => 'sku',
+            'category' => 'PHYSICAL_GOODS',
+            'tax' => [2],
+        ];
+
+        $this->assertEquals($expected, $testee->toArray());
+    }
+}
\ No newline at end of file
diff --git a/modules.local/ppcp-api-client/tests/PHPUnit/Entity/MoneyTest.php b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/MoneyTest.php
new file mode 100644
index 000000000..347210200
--- /dev/null
+++ b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/MoneyTest.php
@@ -0,0 +1,24 @@
+<?php
+declare(strict_types=1);
+
+namespace Inpsyde\PayPalCommerce\ApiClient\Entity;
+
+
+use PHPUnit\Framework\TestCase;
+
+class MoneyTest extends TestCase
+{
+
+    public function test() {
+
+        $testee = new Money(1.10, 'currencyCode');
+        $this->assertEquals(1.10, $testee->value());
+        $this->assertEquals('currencyCode', $testee->currencyCode());
+
+        $expected = [
+            'currency_code' => 'currencyCode',
+            'value' => 1.10,
+        ];
+        $this->assertEquals($expected, $testee->toArray());
+    }
+}
\ No newline at end of file
diff --git a/modules.local/ppcp-api-client/tests/PHPUnit/Entity/PurchaseUnitTest.php b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/PurchaseUnitTest.php
new file mode 100644
index 000000000..42b55e9b2
--- /dev/null
+++ b/modules.local/ppcp-api-client/tests/PHPUnit/Entity/PurchaseUnitTest.php
@@ -0,0 +1,191 @@
+<?php
+declare(strict_types=1);
+
+namespace Inpsyde\PayPalCommerce\ApiClient\Entity;
+
+
+use PHPUnit\Framework\TestCase;
+
+class PurchaseUnitTest extends TestCase
+{
+
+    public function test() {
+
+        $amount = \Mockery::mock(Amount::class);
+        $amount->expects('breakdown')->andReturnNull();
+        $amount->expects('toArray')->andReturn(['amount']);
+        $item1 = \Mockery::mock(Item::class);
+        $item1->expects('toArray')->andReturn(['item1']);
+        $item2 = \Mockery::mock(Item::class);
+        $item2->expects('toArray')->andReturn(['item2']);
+        $shipping = \Mockery::mock(Shipping::class);
+        $shipping->expects('toArray')->andReturn(['shipping']);
+        $testee = new PurchaseUnit(
+            $amount,
+            [],
+            $shipping,
+            'referenceId',
+            'description',
+            null,
+            'customId',
+            'invoiceId',
+            'softDescriptor'
+        );
+
+        $this->assertEquals($amount, $testee->amount());
+        $this->assertEquals('referenceId', $testee->referenceId());
+        $this->assertEquals('description', $testee->description());
+        $this->assertNull($testee->payee());
+        $this->assertEquals('customId', $testee->customId());
+        $this->assertEquals('invoiceId', $testee->invoiceId());
+        $this->assertEquals('softDescriptor', $testee->softDescriptor());
+        $this->assertEquals($shipping, $testee->shipping());
+        $this->assertEquals([], $testee->items());
+
+        $expected = [
+            'reference_id' => 'referenceId',
+            'amount' => ['amount'],
+            'description' => 'description',
+            'items' => [],
+            'shipping' => ['shipping'],
+            'custom_id' => 'customId',
+            'invoice_id' => 'invoiceId',
+            'soft_descriptor' => 'softDescriptor',
+        ];
+
+        $this->assertEquals($expected, $testee->toArray());
+    }
+
+    public function testDontDitchBecauseOfBreakdown() {
+
+        $breakdown = \Mockery::mock(AmountBreakdown::class);
+        $breakdown->expects('shipping')->andReturnNull();
+        $breakdown->expects('itemTotal')->andReturnNull();
+        $breakdown->expects('discount')->andReturnNull();
+        $breakdown->expects('taxTotal')->andReturnNull();
+        $breakdown->expects('shippingDiscount')->andReturnNull();
+        $breakdown->expects('handling')->andReturnNull();
+        $breakdown->expects('insurance')->andReturnNull();
+        $amount = \Mockery::mock(Amount::class);
+        $amount->expects('breakdown')->andReturn($breakdown);
+        $amount->expects('value')->andReturn(0.0);
+        $amount->expects('toArray')->andReturn(['amount']);
+        $item1 = \Mockery::mock(Item::class);
+        $item1->expects('toArray')->andReturn(['item1']);
+        $item2 = \Mockery::mock(Item::class);
+        $item2->expects('toArray')->andReturn(['item2']);
+        $shipping = \Mockery::mock(Shipping::class);
+        $shipping->expects('toArray')->andReturn(['shipping']);
+        $testee = new PurchaseUnit(
+            $amount,
+            [],
+            $shipping,
+            'referenceId',
+            'description',
+            null,
+            'customId',
+            'invoiceId',
+            'softDescriptor'
+        );
+
+        $expected = [
+            'reference_id' => 'referenceId',
+            'amount' => ['amount'],
+            'description' => 'description',
+            'shipping' => ['shipping'],
+            'custom_id' => 'customId',
+            'items' => [],
+            'invoice_id' => 'invoiceId',
+            'soft_descriptor' => 'softDescriptor',
+        ];
+
+        $this->assertEquals($expected, $testee->toArray());
+    }
+
+    public function testDitchBecauseOfBreakdown() {
+
+        $breakdown = \Mockery::mock(AmountBreakdown::class);
+        $breakdown->expects('shipping')->andReturnNull();
+        $breakdown->expects('itemTotal')->andReturnNull();
+        $breakdown->expects('discount')->andReturnNull();
+        $breakdown->expects('taxTotal')->andReturnNull();
+        $breakdown->expects('shippingDiscount')->andReturnNull();
+        $breakdown->expects('handling')->andReturnNull();
+        $breakdown->expects('insurance')->andReturnNull();
+        $amount = \Mockery::mock(Amount::class);
+        $amount->expects('breakdown')->andReturn($breakdown);
+        $amount->expects('value')->andReturn(1.00);
+        $amount->expects('toArray')->andReturn(['amount']);
+        $item1 = \Mockery::mock(Item::class);
+        $item1->expects('toArray')->andReturn(['item1']);
+        $item2 = \Mockery::mock(Item::class);
+        $item2->expects('toArray')->andReturn(['item2']);
+        $shipping = \Mockery::mock(Shipping::class);
+        $shipping->expects('toArray')->andReturn(['shipping']);
+        $testee = new PurchaseUnit(
+            $amount,
+            [],
+            $shipping,
+            'referenceId',
+            'description',
+            null,
+            'customId',
+            'invoiceId',
+            'softDescriptor'
+        );
+
+        $expected = [
+            'reference_id' => 'referenceId',
+            'amount' => ['amount'],
+            'description' => 'description',
+            'shipping' => ['shipping'],
+            'custom_id' => 'customId',
+            'invoice_id' => 'invoiceId',
+            'soft_descriptor' => 'softDescriptor',
+        ];
+
+        $this->assertEquals($expected, $testee->toArray());
+    }
+
+    public function testPayee() {
+
+        $amount = \Mockery::mock(Amount::class);
+        $amount->expects('breakdown')->andReturnNull();
+        $amount->expects('toArray')->andReturn(['amount']);
+        $item1 = \Mockery::mock(Item::class);
+        $item1->expects('toArray')->andReturn(['item1']);
+        $item2 = \Mockery::mock(Item::class);
+        $item2->expects('toArray')->andReturn(['item2']);
+        $shipping = \Mockery::mock(Shipping::class);
+        $shipping->expects('toArray')->andReturn(['shipping']);
+        $payee = \Mockery::mock(Payee::class);
+        $payee->expects('toArray')->andReturn(['payee']);
+        $testee = new PurchaseUnit(
+            $amount,
+            [],
+            $shipping,
+            'referenceId',
+            'description',
+            $payee,
+            'customId',
+            'invoiceId',
+            'softDescriptor'
+        );
+
+        $this->assertEquals($payee, $testee->payee());
+
+        $expected = [
+            'reference_id' => 'referenceId',
+            'amount' => ['amount'],
+            'description' => 'description',
+            'items' => [],
+            'shipping' => ['shipping'],
+            'custom_id' => 'customId',
+            'invoice_id' => 'invoiceId',
+            'soft_descriptor' => 'softDescriptor',
+            'payee' => ['payee'],
+        ];
+
+        $this->assertEquals($expected, $testee->toArray());
+    }
+}
\ No newline at end of file