diff --git a/Sharp7.Tests/TestUtilities.cs b/Sharp7.Tests/TestUtilities.cs
new file mode 100644
index 0000000..f9cd8fb
--- /dev/null
+++ b/Sharp7.Tests/TestUtilities.cs
@@ -0,0 +1,241 @@
+using System;
+using System.Linq.Expressions;
+using Shouldly;
+using Xunit;
+
+namespace Sharp7.Tests
+{
+    public class TestUtilities
+    {
+        [Theory]
+        [InlineData(1,1)] 
+        [InlineData(2,1)] 
+        [InlineData(3,1)] 
+        [InlineData(4,2)] 
+        [InlineData(5,2)] 
+        [InlineData(6,4)] 
+        [InlineData(7,4)] 
+        [InlineData(8,4)] 
+        [InlineData(0x1D,2)] 
+        [InlineData(0x1C,2)] 
+        [InlineData(0,0)] 
+        public void TestDataSizeByte(int wordLength, int expected) { S7.DataSizeByte(wordLength).ShouldBe(expected); }
+        [Fact] public void TestGetBitAt() { S7.GetBitAt(new byte[] {1,2,3,4}, 0, 0).ShouldBe(true); }
+        [Fact] public void TestSetBitAt() {
+            var buffer = new byte[] {1,2,3,4};
+            S7.SetBitAt(ref buffer, 0, 1, true);
+            buffer.ShouldBe(new byte[] {3, 2, 3, 4});
+        }
+
+        //unsigned
+
+        [Theory]
+        [InlineData(new byte[] { 1, 2, 3, 4 }, 0, 1)]
+        [InlineData(new byte[] { 129, 2, 3, 4 }, 0, 129)]
+        public void TestGetUSIntAt(byte[] buffer, int pos, byte expected) { S7.GetUSIntAt(buffer, pos).ShouldBe(expected); }
+        [Theory]
+        [InlineData(new byte[] { 0, 2, 3, 4 }, 0, 1, new byte[] { 1, 2, 3, 4 })]
+        [InlineData(new byte[] { 0, 2, 3, 4 }, 0, 127, new byte[] { 127, 2, 3, 4 })] 
+        public void TestSetUSIntAt(byte[] buffer, int pos, byte value, byte[] expected)
+        {
+            S7.SetUSIntAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData( new byte[] { 1, 1, 0, 0 }, 0, 257)]
+        public void TestGetUIntAt(byte[] buffer, int pos, ushort expected) { S7.GetUIntAt(buffer, pos).ShouldBe(expected); }
+
+        [Theory]
+        [InlineData(new byte[]{0,0,0,0}, 0, 1, new byte[] {0,1,0,0})]
+        public void TestSetUIntAt(byte[] buffer, int pos, ushort value, byte[] expected)
+        {
+            S7.SetUIntAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 2 }, 0, 2)] 
+        public void TestGetUDIntAt(byte[] buffer, int pos, uint expected) { S7.GetUDIntAt(buffer, pos).ShouldBe(expected); }
+
+        [Theory]
+        [InlineData(new byte[] {0, 0, 0, 0}, 0, 1, new byte[] {0, 0, 0, 1})]
+        public void TestSetUDIntAt(byte[] buffer, int pos, uint value, byte[] expected)
+        {
+            S7.SetUDIntAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 2 }, 0, 2L)] 
+        public void TestGetULIntAt(byte[] buffer, int pos, ulong expected) { S7.GetULIntAt(buffer, pos).ShouldBe(expected); }
+
+        [Theory]
+        [InlineData(new byte[] {0, 0, 0, 0, 0, 0, 0, 0}, 0, 1L, new byte[] { 0, 0, 0, 0, 0, 0, 0, 1})]
+        public void TestSetULIntAt(byte[] buffer, int pos, ulong value, byte[] expected)
+        {
+            S7.SetULintAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+        // signed
+
+        [Theory]
+        [InlineData(new byte[] { 1, 2, 3, 4 }, 0, 1)]
+        [InlineData(new byte[] { 129, 2, 3, 4 }, 0, -127)]
+        public void TestGetSIntAt(byte[] buffer, int pos, int expected) { S7.GetSIntAt(buffer, pos).ShouldBe(expected); }
+        [Theory]
+        [InlineData(new byte[] { 0, 2, 3, 4 }, 0, 1, new byte[] { 1, 2, 3, 4 })]
+        [InlineData(new byte[] { 0, 2, 3, 4 }, 0, -127, new byte[] { 129, 2, 3, 4 })]
+        public void TestSetSIntAt(byte[] buffer, int pos, int value, byte[] expected)
+        {
+            S7.SetSIntAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 1, 1, 0, 0 }, 0, 257)]
+        public void TestGetIntAt(byte[] buffer, int pos, int expected) { S7.GetIntAt(buffer, pos).ShouldBe(expected); }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0 }, 0, 1, new byte[] { 0, 1, 0, 0 })]
+        public void TestSetIntAt(byte[] buffer, int pos, Int16 value, byte[] expected)
+        {
+            S7.SetIntAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 2 }, 0, 2)]
+        public void TestGetDIntAt(byte[] buffer, int pos, int expected) { S7.GetDIntAt(buffer, pos).ShouldBe(expected); }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0 }, 0, 1, new byte[] { 0, 0, 0, 1 })]
+        public void TestSetDIntAt(byte[] buffer, int pos, int value, byte[] expected)
+        {
+            S7.SetDIntAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 2 }, 0, 2L)] 
+        public void TestGetLIntAt(byte[] buffer, int pos, long expected) { S7.GetLIntAt(buffer, pos).ShouldBe(expected); }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 }, 0, 1L, new byte[] { 0, 0, 0, 0, 0, 0, 0, 1 })]
+        public void TestSetLIntAt(byte[] buffer, int pos, long value, byte[] expected)
+        {
+            S7.SetLIntAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+
+        [Fact] public void TestGetByteAt() { S7.GetByteAt(new byte[] {1,2,3,4}, 1).ShouldBe((byte)2); }
+
+        [Fact]
+        public void TestSetByteAt()
+        {
+            var buffer = new byte[] { 1, 2, 3, 4 };
+            S7.SetByteAt(buffer, 0, (byte)5);
+            buffer.ShouldBe(new byte[] { 5, 2, 3, 4 });
+        }
+
+        [Theory]
+        [InlineData(new byte[] {0, 2, 0, 0, 0, 0, 0, 0}, 0, 2)]
+        public void TestGetWordAt(byte[] buffer, int pos, ushort expected)
+        {
+            S7.GetWordAt(buffer, pos).ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] {0, 0, 0, 0, 0, 0, 0, 0}, 0, 1, new byte[] {0, 1, 0, 0, 0, 0, 0, 0})]
+        public void TestSetWordAt(byte[] buffer, int pos, ushort value, byte[] expected)
+        {
+            S7.SetWordAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 3, 0, 0, 0, 0 }, 0, 3)]
+        public void TestGetDWordAt(byte[] buffer, int pos, uint expected)
+        {
+            S7.GetDWordAt(buffer, pos).ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 }, 0, 1, new byte[] { 0, 0, 0, 1, 0, 0, 0, 0 })]
+        public void TestSetDWordAt(byte[] buffer, int pos, uint value, byte[] expected)
+        {
+            S7.SetDWordAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 4 }, 0, 4L)]
+        public void TestGetLWordAt(byte[] buffer, int pos, ulong expected)
+        {
+            S7.GetLWordAt(buffer, pos).ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 }, 0, 1L, new byte[] { 0, 0, 0, 0, 0, 0, 0, 1 })]
+        public void TestSetLWordAt(byte[] buffer, int pos, ulong value, byte[] expected)
+        {
+            S7.SetLWordAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 1, 2, 3, 0, 0, 11, 5, 4 }, 0, 2.387938E-38f)]
+        public void TestGetRealAt(byte[] buffer, int pos, float expected)
+        {
+            S7.GetRealAt(buffer, pos).ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 }, 0, 4f, new byte[] { 64, 128, 0, 0, 0, 0, 0, 0 })]
+        public void TestSetRealAt(byte[] buffer, int pos, float value, byte[] expected)
+        {
+            S7.SetRealAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 64, 128, 0, 0, 0, 0, 0, 0}, 0, 512d)]
+        public void TestGetLRealAt(byte[] buffer, int pos, double expected)
+        {
+            S7.GetLRealAt(buffer, pos).ShouldBe(expected);
+        }
+
+        [Theory]
+        [InlineData(new byte[] { 0, 0, 0, 0, 0, 0, 0, 0 }, 0, 4d, new byte[] { 64, 16, 0, 0, 0, 0, 0, 0 })]
+        public void TestSetLRealAt(byte[] buffer, int pos, double value, byte[] expected)
+        {
+            S7.SetLRealAt(buffer, pos, value);
+            buffer.ShouldBe(expected);
+        }
+
+
+        //[Fact] public void TestGetDateTimeAt() { S7.GetDateTimeAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetDateTimeAt() { S7.SetDateTimeAt(new byte[] {1,2,3,4}, int Pos, DateTime Value).ShouldBe(); }
+        //[Fact] public void TestGetDateAt() { S7.GetDateAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetDateAt() { S7.SetDateAt(new byte[] {1,2,3,4}, int Pos, DateTime Value).ShouldBe(); }
+        //[Fact] public void TestGetTODAt() { S7.GetTODAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetTODAt() { S7.SetTODAt(new byte[] {1,2,3,4}, int Pos, DateTime Value).ShouldBe(); }
+        //[Fact] public void TestGetLTODAt() { S7.GetLTODAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetLTODAt() { S7.SetLTODAt(new byte[] {1,2,3,4}, int Pos, DateTime Value).ShouldBe(); }
+        //[Fact] public void TestGetLDTAt() { S7.GetLDTAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetLDTAt() { S7.SetLDTAt(new byte[] {1,2,3,4}, int Pos, DateTime Value).ShouldBe(); }
+        //[Fact] public void TestGetDTLAt() { S7.GetDTLAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetDTLAt() { S7.SetDTLAt(new byte[] {1,2,3,4}, int Pos, DateTime Value).ShouldBe(); }
+
+        //[Fact] public void TestGetStringAt() { S7.GetStringAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetStringAt() { S7.SetStringAt(new byte[] {1,2,3,4}, int Pos, int MaxLen, string Value).ShouldBe(); }
+        //[Fact] public void TestGetCharsAt() { S7.GetCharsAt(new byte[] {1,2,3,4}, int Pos, int Size).ShouldBe(); }
+        //[Fact] public void TestSetCharsAt() { S7.SetCharsAt(new byte[] {1,2,3,4}, int Pos, string Value).ShouldBe(); }
+
+        //[Fact] public void TestGetCounter() { S7.GetCounter(ushort Value).ShouldBe(); }
+        //[Fact] public void TestGetCounterAt() { S7.GetCounterAt(new ushort[] {1,2,3,4}, int Index).ShouldBe(); }
+        //[Fact] public void TestToCounter() { S7.ToCounter(int Value).ShouldBe(); }
+        //[Fact] public void TestSetCounterAt() { S7.SetCounterAt(ushort[] {1,2,3,4}, int Pos, int Value).ShouldBe(); }
+        //[Fact] public void TestGetS7TimerAt() { S7.GetS7TimerAt(new byte[] {1,2,3,4}, int Pos).ShouldBe(); }
+        //[Fact] public void TestSetS7TimespanAt() { S7.SetS7TimespanAt(new byte[] {1,2,3,4}, int Pos, TimeSpan Value).ShouldBe(); }
+        //[Fact] public void TestGetS7TimespanAt() { S7.GetS7TimespanAt(new byte[] {1,2,3,4}, int pos).ShouldBe(); }
+    }
+}
\ No newline at end of file