Add GoodBad C# example project, integration test (#2148)

src/integration-tests/GoodBad/GoodBad.cs

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace GoodBad;
+
+public class BinaryParser
+{
+    int count = 0;
+
+    public void ProcessInput(ReadOnlySpan<byte> data) {
+        if (data.Length < 4) {
+            return;
+        }
+
+        if (data[0] == 'b') { count++; }
+        if (data[1] == 'a') { count++; }
+        if (data[2] == 'd') { count++; }
+        if (data[3] == '!') { count++; }
+
+        // Simulate an out-of-bounds access while parsing.
+        if (count >= 4) {
+            var _ = data[0xdead];
+        }
+    }
+}
+
+public class Fuzzer {
+    /// Preferred test method.
+    public static void TestInput(ReadOnlySpan<byte> data) {
+            var parser = new BinaryParser();
+            parser.ProcessInput(data);
+    }
+
+    /// Backwards-compatible test method for legacy code that can't use `Span` types.
+    ///
+    /// Incurs an extra copy of `data` per fuzzing iteration.
+    public static void TestInputCompat(byte[] data) {
+            var parser = new BinaryParser();
+            parser.ProcessInput(data);
+    }
+
+    /// Invalid static method that has a fuzzing-incompatible signature.
+    public static void BadSignature(ReadOnlySpan<int> data) {
+        return;
+    }
+}

src/integration-tests/GoodBad/GoodBad.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <LangVersion>10.0</LangVersion>
+    <TargetFramework>net6.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+
+</Project>