Improve testability, packaging, and docs

tests/LibNftables.Tests/NftContextTests.cs

@@ -1,5 +1,3 @@
-using System.Globalization;
-
 namespace LibNftables.Tests;
 
 public sealed class NftContextTests
@@ -7,7 +5,7 @@ public sealed class NftContextTests
     [Fact]
     public void ContextFlagsRoundTrip_Works()
     {
-        if (!TryCreateContext(out var ctx))
+        if (!NativeTestSupport.TryCreateContext(out var ctx))
         {
             return;
         }
@@ -38,7 +36,7 @@ public sealed class NftContextTests
     [Fact]
     public void InvalidCommand_ThrowsNftExceptionWithErrorBuffer()
     {
-        if (!TryCreateContext(out var ctx))
+        if (!NativeTestSupport.TryCreateContext(out var ctx))
         {
             return;
         }
@@ -57,12 +55,12 @@ public sealed class NftContextTests
     [Fact]
     public void ValidDryRunCommand_CanExecuteAndBufferOutput()
     {
-        if (!TryCreateContext(out var ctx))
+        if (!NativeTestSupport.TryCreateContext(out var ctx))
         {
             return;
         }
 
-        if (!HasCapNetAdmin())
+        if (!NativeTestSupport.HasCapNetAdmin())
         {
             return;
         }
@@ -82,61 +80,4 @@ public sealed class NftContextTests
         }
     }
 
-    private static bool HasCapNetAdmin()
-    {
-        const int capNetAdminBit = 12;
-        const ulong mask = 1UL << capNetAdminBit;
-
-        try
-        {
-            foreach (var line in File.ReadLines("/proc/self/status"))
-            {
-                if (!line.StartsWith("CapEff:", StringComparison.Ordinal))
-                {
-                    continue;
-                }
-
-                var hex = line["CapEff:".Length..].Trim();
-                if (ulong.TryParse(hex, NumberStyles.AllowHexSpecifier, CultureInfo.InvariantCulture, out var value))
-                {
-                    return (value & mask) != 0;
-                }
-            }
-        }
-        catch
-        {
-            // If capability probing fails, keep test conservative.
-        }
-
-        return false;
-    }
-
-    private static bool TryCreateContext(out NftContext context)
-    {
-        try
-        {
-            context = new NftContext();
-            return true;
-        }
-        catch (DllNotFoundException)
-        {
-            context = null!;
-            return false;
-        }
-        catch (TypeInitializationException ex) when (ex.InnerException is DllNotFoundException)
-        {
-            context = null!;
-            return false;
-        }
-        catch (BadImageFormatException)
-        {
-            context = null!;
-            return false;
-        }
-        catch (EntryPointNotFoundException)
-        {
-            context = null!;
-            return false;
-        }
-    }
 }