diff --git a/tests/unit/NaturallyColorModels/AbstractColorModelUnit.php b/tests/unit/NaturallyColorModels/AbstractColorModelUnit.php
new file mode 100644
index 0000000..844f0bc
--- /dev/null
+++ b/tests/unit/NaturallyColorModels/AbstractColorModelUnit.php
@@ -0,0 +1,82 @@
+<?php /** @noinspection PhpArrayShapeAttributeCanBeAddedInspection */
+
+
+namespace TorstenHettstedt\Colors\Tests\Unit\NaturallyColorModels;
+
+use Codeception\Test\Unit;
+
+abstract class AbstractColorModelUnit extends Unit
+{
+
+    abstract public function testConstruct(): void;
+
+    /**
+     * @return int[][]
+     */
+    public function invalidPercentValueProvider(): array
+    {
+        return [
+            'zu klein' => [-1],
+            'zu gross' => [101],
+        ];
+    }
+
+    /**
+     * @return int[][]
+     */
+    public function validPercentValueProvider(): array
+    {
+        return [
+            'niedrigster Wert' => [0],
+            'mittlerer Wert' => [45],
+            'maximaler Wert' => [100],
+        ];
+    }
+
+    /**
+     * @return int[][]
+     */
+    public function invalidGradValueProvider(): array
+    {
+        return [
+            'zu klein' => [-1],
+            'zu gross' => [361],
+        ];
+    }
+
+    /**
+     * @return int[][]
+     */
+    public function validGradValueProvider(): array
+    {
+        return [
+            'niedrigster Wert' => [0],
+            'mittlerer Wert' => [45],
+            'maximaler Wert' => [360],
+        ];
+    }
+
+    /**
+     * @return int[][]
+     */
+    public function invalidHexadecimalValueProvider(): array
+    {
+        return [
+            'zu klein' => [-0x1],
+            'zu gross' => [0x100],
+        ];
+    }
+
+    /**
+     * @return int[][]
+     */
+    public function validHexadecimalValueProvider(): array
+    {
+        return [
+            'niedrigster Wert' => [0x0],
+            'mittlerer Wert' => [0xD9],
+            'maximaler Wert' => [0xFF],
+        ];
+    }
+
+}
\ No newline at end of file
diff --git a/tests/unit/NaturallyColorModels/CyanMagentaYellowKeyTest.php b/tests/unit/NaturallyColorModels/CyanMagentaYellowKeyTest.php
new file mode 100644
index 0000000..5c2a8a5
--- /dev/null
+++ b/tests/unit/NaturallyColorModels/CyanMagentaYellowKeyTest.php
@@ -0,0 +1,128 @@
+<?php
+
+namespace TorstenHettstedt\Colors\Tests\Unit\NaturallyColorModels;
+
+use InvalidArgumentException;
+use TorstenHettstedt\Colors\NaturallyColorModels\CyanMagentaYellowKey;
+
+class CyanMagentaYellowKeyTest extends AbstractColorModelUnit
+{
+
+    public function testConstruct(): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $this->assertIsInt($color->getCyan());
+        $this->assertEquals(0, $color->getCyan());
+        $this->assertIsInt($color->getMagenta());
+        $this->assertEquals(0, $color->getMagenta());
+        $this->assertIsInt($color->getCyan());
+        $this->assertEquals(0, $color->getYellow());
+        $this->assertIsInt($color->getKey());
+        $this->assertEquals(0, $color->getKey());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validPercentValueProvider
+     */
+    public function testSetCyanWithValidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $color->setCyan($value);
+        $this->assertEquals($value, $color->getCyan());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validPercentValueProvider
+     */
+    public function testSetMagentaWithValidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $color->setMagenta($value);
+        $this->assertEquals($value, $color->getMagenta());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validPercentValueProvider
+     */
+    public function testSetYellowWithValidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $color->setYellow($value);
+        $this->assertEquals($value, $color->getYellow());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validPercentValueProvider
+     */
+    public function testSetKeyWithValidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $color->setKey($value);
+        $this->assertEquals($value, $color->getKey());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidPercentValueProvider
+     */
+    public function testSetCyanWithInvalidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setCyan($value);
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidPercentValueProvider
+     */
+    public function testSetMagentaWithInvalidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setMagenta($value);
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidPercentValueProvider
+     */
+    public function testSetYellowWithInvalidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setYellow($value);
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidPercentValueProvider
+     */
+    public function testSetKeyWithInvalidValue(int $value): void
+    {
+        $color = new CyanMagentaYellowKey();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setKey($value);
+    }
+}
diff --git a/tests/unit/NaturallyColorModels/HueSaturationValueTest.php b/tests/unit/NaturallyColorModels/HueSaturationValueTest.php
new file mode 100644
index 0000000..614e254
--- /dev/null
+++ b/tests/unit/NaturallyColorModels/HueSaturationValueTest.php
@@ -0,0 +1,100 @@
+<?php
+
+namespace TorstenHettstedt\Colors\Tests\Unit\NaturallyColorModels;
+
+use InvalidArgumentException;
+use TorstenHettstedt\Colors\NaturallyColorModels\HueSaturationValue;
+
+class HueSaturationValueTest extends AbstractColorModelUnit
+{
+
+    public function testConstruct(): void
+    {
+        $color = new HueSaturationValue();
+
+        $this->assertIsInt($color->getHue());
+        $this->assertEquals(0, $color->getHue());
+        $this->assertIsInt($color->getSaturation());
+        $this->assertEquals(0, $color->getSaturation());
+        $this->assertIsInt($color->getValue());
+        $this->assertEquals(100, $color->getValue());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validGradValueProvider
+     */
+    public function testSetHueWithValidValue(int $value): void
+    {
+        $color = new HueSaturationValue();
+
+        $color->setHue($value);
+        $this->assertEquals($value, $color->getHue());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidGradValueProvider
+     */
+    public function testSetHueWithInvalidValue(int $value): void
+    {
+        $color = new HueSaturationValue();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setHue($value);
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validPercentValueProvider
+     */
+    public function testSetSaturationWithValidValue(int $value): void
+    {
+        $color = new HueSaturationValue();
+
+        $color->setSaturation($value);
+        $this->assertEquals($value, $color->getSaturation());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidPercentValueProvider
+     */
+    public function testSetSaturationWithInvalidValue(int $value): void
+    {
+        $color = new HueSaturationValue();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setSaturation($value);
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validPercentValueProvider
+     */
+    public function testSetValueWithValidValue(int $value): void
+    {
+        $color = new HueSaturationValue();
+
+        $color->setValue($value);
+        $this->assertEquals($value, $color->getValue());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidPercentValueProvider
+     */
+    public function testSetValueWithInvalidValue(int $value): void
+    {
+        $color = new HueSaturationValue();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setValue($value);
+    }
+}
diff --git a/tests/unit/NaturallyColorModels/RedGreenBlueTest.php b/tests/unit/NaturallyColorModels/RedGreenBlueTest.php
new file mode 100644
index 0000000..f33cb1a
--- /dev/null
+++ b/tests/unit/NaturallyColorModels/RedGreenBlueTest.php
@@ -0,0 +1,109 @@
+<?php
+
+namespace TorstenHettstedt\Colors\Tests\Unit\NaturallyColorModels;
+
+use InvalidArgumentException;
+use TorstenHettstedt\Colors\NaturallyColorModels\RedGreenBlue;
+
+class RedGreenBlueTest extends AbstractColorModelUnit
+{
+
+    public function testConstruct(): void
+    {
+        $color = new RedGreenBlue();
+
+        $this->assertEquals(0xFF, $color->getRed());
+        $this->assertEquals(0xFF, $color->getGreen());
+        $this->assertEquals(0xFF, $color->getBlue());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validHexadecimalValueProvider
+     */
+    public function testSetRedWithValidValue(int $value): void
+    {
+        $color = new RedGreenBlue();
+
+        $color->setRed($value);
+        $this->assertEquals($value, $color->getRed());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidHexadecimalValueProvider
+     */
+    public function testSetRedWithInvalidValue(int $value): void
+    {
+        $color = new RedGreenBlue();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setRed($value);
+    }
+    /**
+     * @param int $value
+     *
+     * @dataProvider validHexadecimalValueProvider
+     */
+    public function testSetGreenWithValidValue(int $value): void
+    {
+        $color = new RedGreenBlue();
+
+        $color->setGreen($value);
+        $this->assertEquals($value, $color->getGreen());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidHexadecimalValueProvider
+     */
+    public function testSetGreenWithInvalidValue(int $value): void
+    {
+        $color = new RedGreenBlue();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setGreen($value);
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider validHexadecimalValueProvider
+     */
+    public function testSetBlueWithValidValue(int $value): void
+    {
+        $color = new RedGreenBlue();
+
+        $color->setBlue($value);
+        $this->assertEquals($value, $color->getBlue());
+    }
+
+    /**
+     * @param int $value
+     *
+     * @dataProvider invalidHexadecimalValueProvider
+     */
+    public function testSetBlueWithInvalidValue(int $value): void
+    {
+        $color = new RedGreenBlue();
+
+        $this->expectException(InvalidArgumentException::class);
+        $color->setBlue($value);
+    }
+
+    public function testHtmlNotation(): void
+    {
+        $color = new RedGreenBlue();
+        $color->setRed(0xA1);
+        $color->setGreen(0xB2);
+        $color->setBlue(0xC3);
+
+        $html = $color->asHtmlNotation();
+
+        $this->assertIsString($html);
+        $this->assertEquals('#A1B2C3', $html);
+    }
+}