diff --git a/src/OpenTK/Math/Quaternion.cs b/src/OpenTK/Math/Quaternion.cs
index bea308bc..0d92d00a 100644
--- a/src/OpenTK/Math/Quaternion.cs
+++ b/src/OpenTK/Math/Quaternion.cs
@@ -66,34 +66,37 @@ namespace OpenTK
         { }
 
         /// <summary>
-        /// Construct a new Quaternion from given Euler angles
+        /// Construct a new Quaternion from given Euler angles in radians. 
+        /// The rotations will get applied in following order:
+        /// 1. around X axis, 2. around Y axis, 3. around Z axis
         /// </summary>
-        /// <param name="pitch">The pitch (attitude), rotation around X axis</param>
-        /// <param name="yaw">The yaw (heading), rotation around Y axis</param>
-        /// <param name="roll">The roll (bank), rotation around Z axis</param>
-        public Quaternion(float pitch, float yaw, float roll)
+        /// <param name="rotationX">Counterclockwise rotation around X axis in radian</param>
+        /// <param name="rotationY">Counterclockwise rotation around Y axis in radian</param>
+        /// <param name="rotationZ">Counterclockwise rotation around Z axis in radian</param>
+        public Quaternion(float rotationX, float rotationY, float rotationZ)
         {
-            yaw *= 0.5f;
-            pitch *= 0.5f;
-            roll *= 0.5f;
+            rotationX *= 0.5f;
+            rotationY *= 0.5f;
+            rotationZ *= 0.5f;
 
-            float c1 = (float)Math.Cos(yaw);
-            float c2 = (float)Math.Cos(pitch);
-            float c3 = (float)Math.Cos(roll);
-            float s1 = (float)Math.Sin(yaw);
-            float s2 = (float)Math.Sin(pitch);
-            float s3 = (float)Math.Sin(roll);
+            float c1 = (float)Math.Cos(rotationX);
+            float c2 = (float)Math.Cos(rotationY);
+            float c3 = (float)Math.Cos(rotationZ);
+            float s1 = (float)Math.Sin(rotationX);
+            float s2 = (float)Math.Sin(rotationY);
+            float s3 = (float)Math.Sin(rotationZ);
 
             W = c1 * c2 * c3 - s1 * s2 * s3;
-            Xyz.X = s1 * s2 * c3 + c1 * c2 * s3;
-            Xyz.Y = s1 * c2 * c3 + c1 * s2 * s3;
-            Xyz.Z = c1 * s2 * c3 - s1 * c2 * s3;
+            Xyz.X = s1 * c2 * c3 + c1 * s2 * s3;
+            Xyz.Y = c1 * s2 * c3 - s1 * c2 * s3;
+            Xyz.Z = c1 * c2 * s3 + s1 * s2 * c3;
         }
 
         /// <summary>
-        /// Construct a new Quaternion from given Euler angles
+        /// Construct a new Quaternion from given Euler angles. The rotations will get applied in following order:
+        /// 1. Around X, 2. Around Y, 3. Around Z
         /// </summary>
-        /// <param name="eulerAngles">The euler angles as a Vector3</param>
+        /// <param name="eulerAngles">The counterclockwise euler angles as a Vector3</param>
         public Quaternion(Vector3 eulerAngles)
             : this(eulerAngles.X, eulerAngles.Y, eulerAngles.Z)
         { }
@@ -407,7 +410,7 @@ namespace OpenTK
         }
 
         /// <summary>
-        /// Build a quaternion from the given axis and angle
+        /// Build a quaternion from the given axis and angle in radians
         /// </summary>
         /// <param name="axis">The axis to rotate about</param>
         /// <param name="angle">The rotation angle in radians</param>
@@ -430,11 +433,13 @@ namespace OpenTK
         }
 
         /// <summary>
-        /// Builds a Quaternion from the given euler angles
+        /// Builds a Quaternion from the given euler angles in radians
+        /// The rotations will get applied in following order:
+        /// 1. pitch (X axis), 2. yaw (Y axis), 3. roll (Z axis)
         /// </summary>
-        /// <param name="pitch">The pitch (attitude), rotation around X axis</param>
-        /// <param name="yaw">The yaw (heading), rotation around Y axis</param>
-        /// <param name="roll">The roll (bank), rotation around Z axis</param>
+        /// <param name="pitch">The pitch (attitude), counterclockwise rotation around X axis</param>
+        /// <param name="yaw">The yaw (heading), counterclockwise rotation around Y axis</param>
+        /// <param name="roll">The roll (bank), counterclockwise rotation around Z axis</param>
         /// <returns></returns>
         public static Quaternion FromEulerAngles(float pitch, float yaw, float roll)
         {
@@ -442,9 +447,11 @@ namespace OpenTK
         }
 
         /// <summary>
-        /// Builds a Quaternion from the given euler angles
+        /// Builds a Quaternion from the given euler angles in radians.
+        /// The rotations will get applied in following order:
+        /// 1. X axis, 2. Y axis, 3. Z axis
         /// </summary>
-        /// <param name="eulerAngles">The euler angles as a vector</param>
+        /// <param name="eulerAngles">The counterclockwise euler angles as a vector</param>
         /// <returns>The equivalent Quaternion</returns>
         public static Quaternion FromEulerAngles(Vector3 eulerAngles)
         {
@@ -452,23 +459,26 @@ namespace OpenTK
         }
 
         /// <summary>
-        /// Builds a Quaternion from the given euler angles
+        /// Builds a Quaternion from the given euler angles in radians.
+        /// The rotations will get applied in following order:
+        /// 1. Around X, 2. Around Y, 3. Around Z
         /// </summary>
-        /// <param name="eulerAngles">The euler angles a vector</param>
+        /// <param name="eulerAngles">The counterclockwise euler angles a vector</param>
         /// <param name="result">The equivalent Quaternion</param>
         public static void FromEulerAngles(ref Vector3 eulerAngles, out Quaternion result)
         {
-            float c1 = (float)Math.Cos(eulerAngles.Y * 0.5f);
-            float c2 = (float)Math.Cos(eulerAngles.X * 0.5f);
+
+            float c1 = (float)Math.Cos(eulerAngles.X * 0.5f);
+            float c2 = (float)Math.Cos(eulerAngles.Y * 0.5f);
             float c3 = (float)Math.Cos(eulerAngles.Z * 0.5f);
-            float s1 = (float)Math.Sin(eulerAngles.Y * 0.5f);
-            float s2 = (float)Math.Sin(eulerAngles.X * 0.5f);
+            float s1 = (float)Math.Sin(eulerAngles.X * 0.5f);
+            float s2 = (float)Math.Sin(eulerAngles.Y * 0.5f);
             float s3 = (float)Math.Sin(eulerAngles.Z * 0.5f);
 
             result.W = c1 * c2 * c3 - s1 * s2 * s3;
-            result.Xyz.X = s1 * s2 * c3 + c1 * c2 * s3;
-            result.Xyz.Y = s1 * c2 * c3 + c1 * s2 * s3;
-            result.Xyz.Z = c1 * s2 * c3 - s1 * c2 * s3;
+            result.Xyz.X = s1 * c2 * c3 + c1 * s2 * s3;
+            result.Xyz.Y = c1 * s2 * c3 - s1 * c2 * s3;
+            result.Xyz.Z = c1 * c2 * s3 + s1 * s2 * c3;
         }
 
         /// <summary>
diff --git a/tests/OpenTK.Tests.Math/DataProviders/QuaternionTestDataGenerator.cs b/tests/OpenTK.Tests.Math/DataProviders/QuaternionTestDataGenerator.cs
new file mode 100644
index 00000000..c01bb252
--- /dev/null
+++ b/tests/OpenTK.Tests.Math/DataProviders/QuaternionTestDataGenerator.cs
@@ -0,0 +1,37 @@
+using System.Collections.Generic;
+
+namespace OpenTK.Tests.Math.DataProviders
+{
+	/// <summary>
+	/// Generates/Provides Quaternion test data.
+	/// </summary>
+	public class QuaternionTestDataGenerator
+	{
+		/// <summary>
+		/// Returns the single axis test cases.
+		/// 1. param: rotation in euler angles
+		/// 2. param: expected result of xyz-component of quaternion
+		/// </summary>
+		/// <value>The single axis test cases.</value>
+		public static IEnumerable<object> SingleAxisTestCases()
+		{
+			yield return new object[] { new Vector3(1, 0, 0), Vector3.UnitX}; //"Rotate around x axis"
+			yield return new object[] { new Vector3(0, 1, 0), Vector3.UnitY}; //"Rotate around y axis" 
+			yield return new object[] { new Vector3(0, 0, 1), Vector3.UnitZ}; //"Rotate around z axis" 
+		}
+
+		/// <summary>
+		/// Returns the single ToAxisAngle test cases.
+		/// 1. param: Quaternion which a definied value of xyz-component.
+		/// 2. param: expected result of xyz-component of quaternion
+		/// </summary>
+		/// <value>The single axis test cases.</value>
+		public static IEnumerable<object[]> ToAxisAngleTestCases()
+		{
+			yield return new object[] { new Quaternion(Vector3.UnitX, 0), Vector3.UnitX}; //"Rotate around x axis"
+			yield return new object[] { new Quaternion(Vector3.UnitY, 0), Vector3.UnitY}; //"Rotate around y axis"
+			yield return new object[] { new Quaternion(Vector3.UnitZ, 0), Vector3.UnitZ}; //"Rotate around z axis"
+		}
+	}
+	
+}
diff --git a/tests/OpenTK.Tests.Math/Helpers/QuaternionTestHelper.cs b/tests/OpenTK.Tests.Math/Helpers/QuaternionTestHelper.cs
new file mode 100644
index 00000000..d3d35dc8
--- /dev/null
+++ b/tests/OpenTK.Tests.Math/Helpers/QuaternionTestHelper.cs
@@ -0,0 +1,61 @@
+using Xunit;
+using System;
+using System.Collections.Generic;
+
+namespace OpenTK.Tests.Math.Helpers
+{
+
+	/// <summary>
+	/// Provides some methods which helps to verify test results
+	/// </summary>
+	internal static class QuaternionTestHelper
+	{
+		/// <summary>
+		/// Verifies the direction of an given <see cref="Vector3"/>.
+		/// </summary>
+		/// <returns>false: When <paramref name="toTest"/> does contain xyz values, when it should be 0,
+		/// or does not contain 0 when it should be</returns>
+		/// <param name="toTest">To test</param>
+		/// <param name="expected">Expected directions. Values getting only 0 checked</param>
+		public static bool VerifyEqualSingleDirection(Vector3 toTest, Vector3 expected)
+		{
+			//To verify the direction of an vector, just respect the 0 values and check against these.
+			//The length of the vectors are ignored.
+			if (expected.X == 0)
+			{
+				if (toTest.X != 0)
+					return false;
+			}
+			else
+			{
+				if (toTest.X == 0)
+					return false;
+			}
+
+			if (expected.Y == 0)
+			{
+				if (toTest.Y != 0)
+					return false;
+			}
+			else
+			{
+				if (toTest.Y == 0)
+					return false;
+			}
+
+			if (expected.Z == 0)
+			{
+				if (toTest.Z != 0)
+					return false;
+			}
+			else
+			{
+				if (toTest.Z == 0)
+					return false;
+			}
+
+			return true;
+		}
+	}
+	
+}
diff --git a/tests/OpenTK.Tests.Math/OpenTK.Tests.Math.csproj b/tests/OpenTK.Tests.Math/OpenTK.Tests.Math.csproj
index 9b2ccec8..71cd5cd6 100644
--- a/tests/OpenTK.Tests.Math/OpenTK.Tests.Math.csproj
+++ b/tests/OpenTK.Tests.Math/OpenTK.Tests.Math.csproj
@@ -47,10 +47,17 @@
   <ItemGroup>
     <Compile Include="BezierCurveTests.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
+    <Compile Include="QuaternionTests.cs" />
+    <Compile Include="Helpers\QuaternionTestHelper.cs" />
+    <Compile Include="DataProviders\QuaternionTestDataGenerator.cs" />
   </ItemGroup>
   <ItemGroup>
     <None Include="paket.references" />
   </ItemGroup>
+  <ItemGroup>
+    <Folder Include="Helpers\" />
+    <Folder Include="Generators\" />
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
diff --git a/tests/OpenTK.Tests.Math/QuaternionTests.cs b/tests/OpenTK.Tests.Math/QuaternionTests.cs
new file mode 100644
index 00000000..ae9a12f5
--- /dev/null
+++ b/tests/OpenTK.Tests.Math/QuaternionTests.cs
@@ -0,0 +1,149 @@
+using Xunit;
+using OpenTK.Tests.Math.Helpers;
+using OpenTK.Tests.Math.DataProviders;
+
+namespace OpenTK.Tests.Math
+{
+	public class QuaternionTests
+	{
+		/// <summary>
+		/// Contains all tests which cover the constructor of Quaternion.
+		/// </summary>
+		public class Constructor
+		{
+			/// <summary>
+			/// Checks if a single given value (either pitch, yaw or roll) get converted into correct x,y,z value of quaternion.
+			/// </summary>
+			/// <param name="eulerValues">euler angle values</param>
+			/// <param name="expectedResult">expected xyz component of quaternion</param>
+			[Theory]
+			[MemberData(nameof(QuaternionTestDataGenerator.SingleAxisTestCases), MemberType = typeof(QuaternionTestDataGenerator))]
+			public void SingleAxisAsEulerAnglesInFloatsIsConvertedToCorrectQuaternionComponents
+			(Vector3 eulerValues, Vector3 expectedResult)
+			{
+				//Arrange + Act: Create Quaternion with "pitch/yaw/roll"
+				var cut = new Quaternion(eulerValues.X, eulerValues.Y, eulerValues.Z);
+
+				//Assert: Use helper, to check if part of the two correct axis is zero. I just want check the direction
+				Vector3 resultXYZ = cut.Xyz;
+
+				Assert.True(QuaternionTestHelper.VerifyEqualSingleDirection(resultXYZ, expectedResult));
+			}
+
+			/// <summary>
+			/// Checks if a single given value (either pitch, yaw or roll) get converted into correct x,y,z value of quaternion.
+			/// </summary>
+			/// <param name="eulerValues">euler angle values</param>
+			/// <param name="expectedResult">expected xyz component of quaternion</param>
+			[Theory]
+			[MemberData(nameof(QuaternionTestDataGenerator.SingleAxisTestCases), MemberType = typeof(QuaternionTestDataGenerator))]
+			public void SingleAxisAsEulerAnglesInVector3IsConvertedToCorrectQuaternionComponents
+			(Vector3 eulerValues, Vector3 expectedResult)
+			{
+				//Arrange + Act: Create Quaternion with "pitch/yaw/roll"
+				var cut = new Quaternion(eulerValues);
+
+				//Assert: Use helper, to check if part of the two correct axis is zero. I just want check the direction
+				Vector3 resultXYZ = cut.Xyz;
+
+				Assert.True(QuaternionTestHelper.VerifyEqualSingleDirection(resultXYZ, expectedResult));
+			}
+
+			//TODO: Make also checks with ccw rotation angle and correct applied rotation order of multiple axis
+		}
+
+		/// <summary>
+		/// Contains all tests for FromEulerAngles
+		/// </summary>
+		public class FromEulerAngles
+		{
+			/// <summary>
+			/// Checks if a single given value (either pitch, yaw or roll) get converted into correct x,y,z value of quaternion.
+			/// </summary>
+			/// <param name="eulerValues">euler angle values</param>
+			/// <param name="expectedResult">expected xyz component of quaternion</param>
+			[Theory]
+			[MemberData(nameof(QuaternionTestDataGenerator.SingleAxisTestCases), MemberType = typeof(QuaternionTestDataGenerator))]
+			public void SingleAxisAsEulerAnglesInFloatsIsConvertedToCorrectQuaternionComponents
+			(Vector3 eulerValues, Vector3 expectedResult)
+			{
+				//Arrange + Act: Create Quaternion with "pitch/yaw/roll"
+				var cut = Quaternion.FromEulerAngles(eulerValues.X, eulerValues.Y, eulerValues.Z);
+
+				//Assert: Use helper, to check if part of the two correct axis is zero. I just want check the direction
+				Vector3 resultXYZ = cut.Xyz;
+
+				Assert.True(QuaternionTestHelper.VerifyEqualSingleDirection(resultXYZ, expectedResult));
+			}
+
+			/// <summary>
+			/// Checks if a single given value (either pitch, yaw or roll) get converted into correct x,y,z value of quaternion.
+			/// </summary>
+			/// <param name="eulerValues">euler angle values</param>
+			/// <param name="expectedResult">expected xyz component of quaternion</param>
+			[Theory]
+			[MemberData(nameof(QuaternionTestDataGenerator.SingleAxisTestCases), MemberType = typeof(QuaternionTestDataGenerator))]
+			public void SingleAxisAsEulerAnglesInVector3IsConvertedToCorrectQuaternionComponents
+			(Vector3 eulerValues, Vector3 expectedResult)
+			{
+				//Arrange + Act: Create Quaternion with "pitch/yaw/roll"
+				var cut = Quaternion.FromEulerAngles(eulerValues);
+
+				//Assert: Use helper, to check if part of the two correct axis is zero. I just want check the direction
+				Vector3 resultXYZ = cut.Xyz;
+
+				Assert.True(QuaternionTestHelper.VerifyEqualSingleDirection(resultXYZ, expectedResult));
+			}
+
+			/// <summary>
+			/// Checks if a single given value (either pitch, yaw or roll) get converted into correct x,y,z value of quaternion.
+			/// </summary>
+			/// <param name="eulerValues">euler angle values</param>
+			/// <param name="expectedResult">expected xyz component of quaternion</param>
+			[Theory]
+			[MemberData(nameof(QuaternionTestDataGenerator.SingleAxisTestCases), MemberType = typeof(QuaternionTestDataGenerator))]
+			public void SingleAxisAsEulerAnglesInVector3IsConvertedToCorrectQuaternionComponentsAsOutParam
+			(Vector3 eulerValues, Vector3 expectedResult)
+			{
+				//Arrange + Act: Create Quaternion with "pitch/yaw/roll"
+				var cut = Quaternion.Identity;
+				Quaternion.FromEulerAngles(ref eulerValues, out cut);
+
+				//Assert: Use helper, to check if part of the two correct axis is zero. I just want check the direction
+				Vector3 resultXYZ = cut.Xyz;
+
+				Assert.True(QuaternionTestHelper.VerifyEqualSingleDirection(resultXYZ, expectedResult));
+			}
+
+			//TODO: Make also checks with ccw rotation angle and correct applied rotation order of multiple axis
+		}
+
+
+		/// <summary>
+		/// Contains all test for ToAxisAngle
+		/// </summary>
+		public class ToAxisAngle
+		{
+			/// <summary>
+			/// Check if a quaternion returns a a rotation about the correct coordinate axis
+			/// </summary>
+			/// <param name="cut">Prepared Quaternion</param>
+			/// <param name="expectedResult">Expected result.</param>
+			[Theory]
+			[MemberData(nameof(QuaternionTestDataGenerator.ToAxisAngleTestCases), MemberType = typeof(QuaternionTestDataGenerator))]
+			public void PreparedSingleRotationAxisQuaternionConvertsToCorrectAxisAngleRepresentation(Quaternion cut, Vector3 expectedResult)
+			{
+				//Arrange + Act: Create Quaternion with rotation about X/Y/Z axis
+				Vector3 resultXYZ;
+				float dontCare;
+				cut.ToAxisAngle(out resultXYZ, out dontCare);
+
+				//Assert: Use helper, to check if part of the two correct axis is zero. I just want check the direction
+				Assert.True(QuaternionTestHelper.VerifyEqualSingleDirection(resultXYZ, expectedResult));
+			}
+
+			//TODO: Make also checks with ccw rotation angle and correct applied rotation order of multiple axis
+		}
+	}
+}
+