diff --git a/CHANGELOG.md b/CHANGELOG.md
index 540e019..9ea690e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,7 +1,7 @@
-## v2.2.1 (xxx)
+## v2.2.1 (November 2nd, 2023)
 - Drop support of php < 7.4
 
-## v2.2.0 (Feb 17th, 2021)
+## v2.2.0 (February 17th, 2021)
 - Added support for php 8.0
 - Added option power factor for Si factor, ie for square (2) and cubic (3)
 - Added new Physical Quantity volume flow with commonly used units
diff --git a/tests/PhysicalQuantity/AccelerationTest.php b/tests/PhysicalQuantity/AccelerationTest.php
index 5732ef2..76bf800 100644
--- a/tests/PhysicalQuantity/AccelerationTest.php
+++ b/tests/PhysicalQuantity/AccelerationTest.php
@@ -21,13 +21,13 @@ protected function instantiateTestQuantity(): PhysicalQuantityInterface
         return new Acceleration(1, 'm/s^2');
     }
 
-    public function testToKiloMeterPerSecond()
+    public function testToKiloMeterPerSecond(): void
     {
         $value = new Acceleration(1000, 'm/s^2');
         $this->assertEquals(1, $value->toUnit('km/s^2'));
     }
 
-    public function testToMilliMeterPerSecond()
+    public function testToMilliMeterPerSecond(): void
     {
         $value = new Acceleration(1, 'm/s^2');
         $this->assertEquals(1000, $value->toUnit('mm/s^2'));
diff --git a/tests/PhysicalQuantity/AreaTest.php b/tests/PhysicalQuantity/AreaTest.php
index 260245b..9d8f3dc 100644
--- a/tests/PhysicalQuantity/AreaTest.php
+++ b/tests/PhysicalQuantity/AreaTest.php
@@ -199,7 +199,7 @@ public function testToDecare(): void
         $this->assertEquals(1, $area->toUnit('decare'));
     }
 
-    public function testToDecimeterSquare()
+    public function testToDecimeterSquare(): void
     {
         $area = new Area(1, 'm^2');
         $this->assertEquals(100, $area->toUnit('dm^2'));
@@ -207,7 +207,7 @@ public function testToDecimeterSquare()
         $this->assertEquals(10000, $area->toUnit('dm^2'));
     }
 
-    public function testToMillimeterSquare()
+    public function testToMillimeterSquare(): void
     {
         $area = new Area(1, 'm^2');
         $this->assertEquals(1e6, $area->toUnit('mm^2'));
diff --git a/tests/PhysicalQuantity/EnergyTest.php b/tests/PhysicalQuantity/EnergyTest.php
index 1a46534..bbbba7f 100644
--- a/tests/PhysicalQuantity/EnergyTest.php
+++ b/tests/PhysicalQuantity/EnergyTest.php
@@ -102,13 +102,13 @@ public function testToJoule(): void
         $this->assertEquals(3600, $quantity->toUnit('joule'));
     }
 
-    public function testToMegaCal()
+    public function testToMegaCal(): void
     {
         $quantity = new Energy(1, 'kWh');
         $this->assertEquals(0.8604206500956023, $quantity->toUnit('Mcal'));
     }
 
-    public function testToMegaElectronvolt()
+    public function testToMegaElectronvolt(): void
     {
         $quantity = new Energy(1, 'kWh');
         $this->assertEquals(2.2469432853179728e19, $quantity->toUnit('MeV'));
diff --git a/tests/PhysicalQuantity/LengthTest.php b/tests/PhysicalQuantity/LengthTest.php
index db4dd61..5901248 100644
--- a/tests/PhysicalQuantity/LengthTest.php
+++ b/tests/PhysicalQuantity/LengthTest.php
@@ -245,19 +245,19 @@ public function testToAstronomicalUnit(): void
         $this->assertEquals(1.0026880683402668, $quantity->toUnit('AU'));
     }
 
-    public function testToLightYear()
+    public function testToLightYear(): void
     {
         $quantity = new Length(150000000000000, 'km');
         $this->assertEquals(15.855012510369232, $quantity->toUnit('ly'));
     }
 
-    public function testToParSec()
+    public function testToParSec(): void
     {
         $quantity = new Length(150000000000000, 'km');
         $this->assertEquals(4.861168934166548, $quantity->toUnit('pc'));
     }
 
-    public function testToMilliParSec()
+    public function testToMilliParSec(): void
     {
         $quantity = new Length(150000000000000, 'km');
         $this->assertEquals(4861.168934166548, $quantity->toUnit('mpc'));
diff --git a/tests/PhysicalQuantity/MassTest.php b/tests/PhysicalQuantity/MassTest.php
index 8126f41..9387ecf 100644
--- a/tests/PhysicalQuantity/MassTest.php
+++ b/tests/PhysicalQuantity/MassTest.php
@@ -131,27 +131,27 @@ public function testToStones(): void
         $this->assertEquals(1, $quantity->toUnit('st'));
     }
 
-    public function testToHundredweight()
+    public function testToHundredweight(): void
     {
         $quantity = new Mass(5, 'kg');
-        $this->assertEquals(0.098420653, $quantity->toUnit('cwt'), '', 0.00000001);
+        $this->assertEqualsWithDelta(0.098420653, $quantity->toUnit('cwt'), '', 0.00000001);
     }
 
-    public function testToUSshortTon()
+    public function testToUSshortTon(): void
     {
         $quantity = new Mass(5, 'kg');
-        $this->assertEquals(0.0055115566, $quantity->toUnit('ust'), '', 0.000000001);
+        $this->assertEqualsWithDelta(0.0055115566, $quantity->toUnit('ust'), '', 0.000000001);
     }
 
-    public function testToUSlongTon()
+    public function testToUSlongTon(): void
     {
         $quantity = new Mass(5, 'kg');
-        $this->assertEquals(0.0049210326, $quantity->toUnit('ukt'), '', 0.000000001);
+        $this->assertEqualsWithDelta(0.0049210326, $quantity->toUnit('ukt'), '', 0.000000001);
     }
 
-    public function testToPicul()
+    public function testToPicul(): void
     {
         $quantity = new Mass(5, 'kg');
-        $this->assertEquals(0.08267335, $quantity->toUnit('picul'), '', 0.00000001);
+        $this->assertEqualsWithDelta(0.08267335, $quantity->toUnit('picul'), '', 0.00000001);
     }
 }
diff --git a/tests/PhysicalQuantity/PowerTest.php b/tests/PhysicalQuantity/PowerTest.php
index 3a52a1a..455fd5d 100644
--- a/tests/PhysicalQuantity/PowerTest.php
+++ b/tests/PhysicalQuantity/PowerTest.php
@@ -51,7 +51,7 @@ public function testToWatt(): void
         $this->assertEquals(1000, $quantity->toUnit('W'));
     }
 
-    public function testToDecibelsMilliWatt()
+    public function testToDecibelsMilliWatt(): void
     {
         $quantity = new Power(0.01, 'mW');
         $this->assertEquals(-20, $quantity->toUnit('dBm'));
@@ -61,7 +61,7 @@ public function testToDecibelsMilliWatt()
         $this->assertEquals(70, $quantity->toUnit('dBm'));
     }
 
-    public function testFromDecibelsMilliWatt()
+    public function testFromDecibelsMilliWatt(): void
     {
         $quantity = new Power(-20, 'dBm');
         $this->assertEquals(0.00001, $quantity->toUnit('W'));
diff --git a/tests/PhysicalQuantity/StorageTest.php b/tests/PhysicalQuantity/StorageTest.php
index da1c574..9c55558 100644
--- a/tests/PhysicalQuantity/StorageTest.php
+++ b/tests/PhysicalQuantity/StorageTest.php
@@ -3,46 +3,47 @@
 namespace PhpUnitsOfMeasureTest\PhysicalQuantity;
 
 use PhpUnitsOfMeasure\PhysicalQuantity\Storage;
+use PhpUnitsOfMeasure\PhysicalQuantityInterface;
 
 class StorageTest extends AbstractPhysicalQuantityTestCase
 {
 
-    protected function instantiateTestQuantity()
+    protected function instantiateTestQuantity(): PhysicalQuantityInterface
     {
         return new Storage(1, 'byte');
     }
 
-    public function testByteToByte()
+    public function testByteToByte(): void
     {
         $this->assertEquals(1, (new Storage(1, 'byte'))->toUnit('B'));
     }
 
-    public function testByteToBit()
+    public function testByteToBit(): void
     {
         $this->assertEquals(40, (new Storage(5, 'byte'))->toUnit('bit'));
     }
 
-    public function testBitToByte()
+    public function testBitToByte(): void
     {
         $this->assertEquals(1.25, (new Storage(10, 'b'))->toUnit('B'));
     }
 
-    public function testMegabyteToByte()
+    public function testMegabyteToByte(): void
     {
         $this->assertEquals(1048576, (new Storage(1, 'MB'))->toUnit('B'));
     }
 
-    public function testGigabyteToByte()
+    public function testGigabyteToByte(): void
     {
         $this->assertEquals(1073741824, (new Storage(1, 'gigabyte'))->toUnit('byte'));
     }
 
-    public function testTerabyteToByte()
+    public function testTerabyteToByte(): void
     {
         $this->assertEquals(1099511627776, (new Storage(1, 'TB'))->toUnit('byte'));
     }
 
-    public function testPetabyteToByte()
+    public function testPetabyteToByte(): void
     {
         $this->assertEquals(3377699720527872, (new Storage(3, 'PB'))->toUnit('byte'));
     }
diff --git a/tests/PhysicalQuantity/TemperatureTest.php b/tests/PhysicalQuantity/TemperatureTest.php
index f8a65cf..7d9c49a 100644
--- a/tests/PhysicalQuantity/TemperatureTest.php
+++ b/tests/PhysicalQuantity/TemperatureTest.php
@@ -85,44 +85,44 @@ protected function instantiateTestQuantity(): PhysicalQuantityInterface
         return new Temperature(1, 'K');
     }
 
-    public function testToCelsius()
+    public function testToCelsius(): void
     {
         $value = new Temperature(313.15, 'K');
-        $this->assertEquals(40, $value->toUnit('C'), '', 0.000001);
+        $this->assertEqualsWithDelta(40, $value->toUnit('C'), '', 0.000001);
     }
 
-    public function testToFahrenheit()
+    public function testToFahrenheit(): void
     {
         $value = new Temperature(313.15, 'K');
-        $this->assertEquals(104, $value->toUnit('F'), '', 0.000001);
+        $this->assertEqualsWithDelta(104, $value->toUnit('F'), '', 0.000001);
     }
 
-    public function testToRankine()
+    public function testToRankine(): void
     {
         $value = new Temperature(313.15, 'K');
-        $this->assertEquals(563.67, $value->toUnit('Ra'), '', 0.000001);
+        $this->assertEqualsWithDelta(563.67, $value->toUnit('Ra'), '', 0.000001);
     }
-    public function testToDelisle()
+    public function testToDelisle(): void
     {
         $value = new Temperature(313.15, 'K');
-        $this->assertEquals(90, $value->toUnit('D'), '', 0.000001);
+        $this->assertEqualsWithDelta(90, $value->toUnit('D'), '', 0.000001);
     }
 
-    public function testToNewton()
+    public function testToNewton(): void
     {
         $value = new Temperature(313.15, 'K');
-        $this->assertEquals(13.2, $value->toUnit('N'), '', 0.000001);
+        $this->assertEqualsWithDelta(13.2, $value->toUnit('N'), '', 0.000001);
     }
 
-    public function testToReaumur()
+    public function testToReaumur(): void
     {
         $value = new Temperature(313.15, 'K');
-        $this->assertEquals(32, $value->toUnit('Re'), '', 0.000001);
+        $this->assertEqualsWithDelta(32, $value->toUnit('Re'), '', 0.000001);
     }
 
-    public function testToRomer()
+    public function testToRomer(): void
     {
         $value = new Temperature(313.15, 'K');
-        $this->assertEquals(28.5, $value->toUnit('Ro'), '', 0.000001);
+        $this->assertEqualsWithDelta(28.5, $value->toUnit('Ro'), '', 0.000001);
     }
 }
diff --git a/tests/PhysicalQuantity/VelocityTest.php b/tests/PhysicalQuantity/VelocityTest.php
index ffaa9bc..30df26b 100644
--- a/tests/PhysicalQuantity/VelocityTest.php
+++ b/tests/PhysicalQuantity/VelocityTest.php
@@ -38,7 +38,7 @@ protected function instantiateTestQuantity(): PhysicalQuantityInterface
     public function testToKilometersPerHour(): void
     {
         $speed = new Velocity(1, 'km/h');
-        $this->assertEquals(0.277778, $speed->toUnit('m/s'), '', 0.000001);
+        $this->assertEqualsWithDelta(0.277778, $speed->toUnit('m/s'), '', 0.000001);
     }
 
     public function testToFeetPerSecond(): void
@@ -50,7 +50,7 @@ public function testToFeetPerSecond(): void
     public function testToKmPerHour(): void
     {
         $speed = new Velocity(2, 'mph');
-        $this->assertEquals(3.218688, $speed->toUnit('km/h'), '', 0.000001);
+        $this->assertEqualsWithDelta(3.218688, $speed->toUnit('km/h'), '', 0.000001);
     }
 
     public function testToKnot(): void
@@ -59,9 +59,9 @@ public function testToKnot(): void
         $this->assertEquals(3.8876923435786983, $speed->toUnit('knot'));
     }
 
-    public function testToMach()
+    public function testToMach(): void
     {
         $speed = new Velocity(1000, 'm/s');
-        $this->assertEquals(2.906977, $speed->toUnit('mach'), '', 0.000001);
+        $this->assertEqualsWithDelta(2.906977, $speed->toUnit('mach'), '', 0.000001);
     }
 }
diff --git a/tests/PhysicalQuantity/VolumeFlowTest.php b/tests/PhysicalQuantity/VolumeFlowTest.php
index 1f02ba9..34f28f0 100644
--- a/tests/PhysicalQuantity/VolumeFlowTest.php
+++ b/tests/PhysicalQuantity/VolumeFlowTest.php
@@ -3,10 +3,11 @@
 namespace PhpUnitsOfMeasureTest\PhysicalQuantity;
 
 use PhpUnitsOfMeasure\PhysicalQuantity\VolumeFlow;
+use PhpUnitsOfMeasure\PhysicalQuantityInterface;
 
 class VolumeFlowTest extends AbstractPhysicalQuantityTestCase
 {
-    protected $supportedUnitsWithAliases = [
+    protected array $supportedUnitsWithAliases = [
         'm^3/s',
         'm³/s',
         'cubic meter per second',
@@ -331,12 +332,12 @@ class VolumeFlowTest extends AbstractPhysicalQuantityTestCase
         'us gal/d'
     ];
 
-    protected function instantiateTestQuantity()
+    protected function instantiateTestQuantity(): PhysicalQuantityInterface
     {
         return new VolumeFlow(1, 'm^3/s');
     }
 
-    public function testToCubicDecimeterSecond()
+    public function testToCubicDecimeterSecond(): void
     {
         $area = new VolumeFlow(1, 'm^3/s');
         /*
@@ -353,15 +354,15 @@ public function testToCubicDecimeterSecond()
     }
 
 
-    public function testToCubicMillimeterSecond()
+    public function testToCubicMillimeterSecond(): void
     {
         $area = new VolumeFlow(1, 'm^3/s');
-        $this->assertEquals(1e9, $area->toUnit('mm^3/s'), '', 0.000001);
+        $this->assertEqualsWithDelta(1e9, $area->toUnit('mm^3/s'), '', 0.000001);
         $area = new VolumeFlow(100, 'm^3/s');
         $this->assertEquals(1e11, $area->toUnit('mm^3/s'));
     }
 
-    public function testToLitresSecond()
+    public function testToLitresSecond(): void
     {
         $area = new VolumeFlow(1, 'm^3/s');
         $this->assertEquals(1000, $area->toUnit('l/s'));
@@ -369,7 +370,7 @@ public function testToLitresSecond()
         $this->assertEquals(100000, $area->toUnit('l/s'));
     }
 
-    public function testToMilliLitresSecond()
+    public function testToMilliLitresSecond(): void
     {
         $area = new VolumeFlow(1, 'l/s');
         $this->assertEquals(1000, $area->toUnit('ml/s'));
@@ -377,7 +378,7 @@ public function testToMilliLitresSecond()
         $this->assertEquals(100000, $area->toUnit('ml/s'));
     }
 
-    public function testToHectoLitresSecond()
+    public function testToHectoLitresSecond(): void
     {
         $area = new VolumeFlow(1, 'l/s');
         $this->assertEquals(0.01, $area->toUnit('hl/s'));
@@ -385,7 +386,7 @@ public function testToHectoLitresSecond()
         $this->assertEquals(1, $area->toUnit('hl/s'));
     }
 
-    public function testToKiloLitresSecond()
+    public function testToKiloLitresSecond(): void
     {
         $area = new VolumeFlow(1, 'l/s');
         $this->assertEquals(0.001, $area->toUnit('kl/s'));
@@ -396,8 +397,8 @@ public function testToKiloLitresSecond()
     public function testToCFM()
     {
         $area = new VolumeFlow(1, 'CMM');
-        $this->assertEquals(35.314667, $area->toUnit('CFM'), '', 0.000001);
+        $this->assertEqualsWithDelta(35.314667, $area->toUnit('CFM'), '', 0.000001);
         $area = new VolumeFlow(100, 'm^3/s');
-        $this->assertEquals(211888.000328, $area->toUnit('CFM'), '', 0.000001);
+        $this->assertEqualsWithDelta(211888.000328, $area->toUnit('CFM'), '', 0.000001);
     }
 }
diff --git a/tests/PhysicalQuantity/VolumeTest.php b/tests/PhysicalQuantity/VolumeTest.php
index 4be4708..c247a8c 100644
--- a/tests/PhysicalQuantity/VolumeTest.php
+++ b/tests/PhysicalQuantity/VolumeTest.php
@@ -90,7 +90,7 @@ protected function instantiateTestQuantity(): PhysicalQuantityInterface
         return new Volume(1, 'm^3');
     }
 
-    public function testToCubicDecimeter()
+    public function testToCubicDecimeter(): void
     {
         $area = new Volume(1, 'm^3');
         $this->assertEquals(1000, $area->toUnit('dm^3'));
@@ -98,15 +98,15 @@ public function testToCubicDecimeter()
         $this->assertEquals(100000, $area->toUnit('dm^3'));
     }
 
-    public function testToCubicMillimeter()
+    public function testToCubicMillimeter(): void
     {
         $area = new Volume(1, 'm^3');
-        $this->assertEquals(1e9, $area->toUnit('mm^3'), '', 0.000001);
+        $this->assertEqualsWithDelta(1e9, $area->toUnit('mm^3'), '', 0.000001);
         $area = new Volume(100, 'm^3');
         $this->assertEquals(1e11, $area->toUnit('mm^3'));
     }
 
-    public function testToLitres()
+    public function testToLitres(): void
     {
         $area = new Volume(1, 'm^3');
         $this->assertEquals(1000, $area->toUnit('l'));
@@ -114,7 +114,7 @@ public function testToLitres()
         $this->assertEquals(100000, $area->toUnit('l'));
     }
 
-    public function testToMilliLitres()
+    public function testToMilliLitres(): void
     {
         $area = new Volume(1, 'l');
         $this->assertEquals(1000, $area->toUnit('ml'));
@@ -122,7 +122,7 @@ public function testToMilliLitres()
         $this->assertEquals(100000, $area->toUnit('ml'));
     }
 
-    public function testToHectoLitres()
+    public function testToHectoLitres(): void
     {
         $area = new Volume(1, 'l');
         $this->assertEquals(0.01, $area->toUnit('hl'));
@@ -130,7 +130,7 @@ public function testToHectoLitres()
         $this->assertEquals(1, $area->toUnit('hl'));
     }
 
-    public function testToKiloLitres()
+    public function testToKiloLitres(): void
     {
         $area = new Volume(1, 'l');
         $this->assertEquals(0.001, $area->toUnit('kl'));
@@ -138,11 +138,11 @@ public function testToKiloLitres()
         $this->assertEquals(0.1, $area->toUnit('kl'));
     }
 
-    public function testToGallon()
+    public function testToGallon(): void
     {
         $area = new Volume(1, 'm^3');
-        $this->assertEquals(264.172051, $area->toUnit('gal'), '', 0.000001);
+        $this->assertEqualsWithDelta(264.172051, $area->toUnit('gal'), '', 0.000001);
         $area = new Volume(100, 'm^3');
-        $this->assertEquals(26417.205124, $area->toUnit('gal'), '', 0.000001);
+        $this->assertEqualsWithDelta(26417.205124, $area->toUnit('gal'), '', 0.000001);
     }
 }