Yep, ASCII has its own problems indeed.

- added more tests to check characters converted to bytes with different encoding

Author: Michal-MK

exampleTest/BinaryTest.cs

@@ -1,6 +1,7 @@
 using System;
 using System.IO;
 using System.Linq;
+using System.Text;
 using Xunit;
 
 namespace CheckTestOutput.Example
@@ -25,9 +26,10 @@ public void CheckModifiedBinaryData()
             byte[] previousData = File.ReadAllBytes(imgPath);
             byte[] modifiedData = previousData.Append((byte)64).ToArray();
 
-            //File contents do not match
+            // File contents do not match
             Assert.Throws<Exception>(() => check.CheckBinary(modifiedData));
 
+            // Return back the original content
             File.WriteAllBytes(Path.Combine(check.CheckDirectory, $"{nameof(BinaryTest)}.{nameof(CheckModifiedBinaryData)}.bin"), previousData);
         }
 
@@ -38,5 +40,23 @@ public void CheckNonexistentBinaryData()
             // File does not exist
             Assert.Throws<ArgumentNullException>(() => check.CheckBinary(imageBytes));
         }
+        
+        [Fact]
+        public void CheckUTF8TextConvertedToBinaryData()
+        {
+            const string TEXT = "( ͡° ͜ʖ ͡°)";
+
+            check.CheckBinary(Encoding.UTF8.GetBytes(TEXT));
+            Assert.True(true);
+        }   
+        
+
+        [Fact]
+        public void CheckUTF8TextConvertedWithASCIIBinaryDataThrows()
+        {
+            const string TEXT = "( ͡° ͜ʖ ͡°)";
+
+            Assert.Throws<Exception>(() => check.CheckBinary(Encoding.ASCII.GetBytes(TEXT)));
+        }
     }
 }

exampleTest/testoutputs/BinaryTest.CheckUTF8TextConvertedToBinaryData.bin

@@ -0,0 +1 @@
+( ͡° ͜ʖ ͡°)

exampleTest/testoutputs/BinaryTest.CheckUTF8TextConvertedWithASCIIBinaryDataThrows.bin

@@ -0,0 +1 @@
+( ͡° ͜ʖ ͡°)

src/OutputChecker.cs

@@ -83,7 +83,7 @@ public OutputChecker(
 
         private readonly Lazy<bool> DoesGitWork;
 
-        private Process StartGitProcess(System.Text.Encoding encoding, params string[] args)
+        private Process StartGitProcess(params string[] args)
         {
 #if DEBUG
             Console.WriteLine("Running git command: " + string.Join(" ", args));
@@ -97,8 +97,8 @@ private Process StartGitProcess(System.Text.Encoding encoding, params string[] a
                 RedirectStandardError = true,
                 RedirectStandardInput = true,
                 CreateNoWindow = true,
-                StandardOutputEncoding = encoding,
-                StandardErrorEncoding = encoding,
+                StandardOutputEncoding = System.Text.Encoding.UTF8,
+                StandardErrorEncoding = System.Text.Encoding.UTF8,
             };
             foreach (var a in args)
                 procInfo.ArgumentList.Add(a);
@@ -125,7 +125,7 @@ private void HandleProcessExit(Process proc, Task outputReaderTask, params strin
 
         private string[] RunGitCommand(params string[] args)
         {
-            var proc = StartGitProcess(System.Text.Encoding.UTF8, args);
+            var proc = StartGitProcess(args);
 
             var outputLines = new List<string>();
             var outputReaderTask = Task.Run(() =>
@@ -147,24 +147,24 @@ private byte[] RunGitBinaryCommand(params string[] args)
         {
             const int BUFFER_SIZE = 1024;
 
-            var proc = StartGitProcess(System.Text.Encoding.ASCII, args);
+            var proc = StartGitProcess(args);
 
-            List<char> ret = new();
+            List<byte> ret = new();
 
             var outputReaderTask = Task.Run(() =>
             {
-                char[] buffer = new char[BUFFER_SIZE];
+                byte[] buffer = new byte[BUFFER_SIZE];
 
                 int charsRead = 0;
-                while ((charsRead = proc.StandardOutput.ReadBlock(buffer, 0, BUFFER_SIZE)) != 0)
+                while ((charsRead = proc.StandardOutput.BaseStream.Read(buffer, 0, BUFFER_SIZE)) != 0)
                 {
                     ret.AddRange(buffer.AsSpan(0, charsRead).ToArray());
                 }
             });
 
             HandleProcessExit(proc, outputReaderTask, args);
 
-            return ret.ConvertAll(c => (byte)c).ToArray();
+            return ret.ToArray();
         }
 
         static string[] ReadAllLines(StreamReader reader)