add fake connection to C API

crates/servicepoint_binding_c/src/connection.rs

@@ -46,6 +46,22 @@ pub unsafe extern "C" fn sp_connection_open(
     Box::into_raw(Box::new(SPConnection(connection)))
 }
 
+/// Creates a new instance of [SPConnection] for testing that does not actually send anything.
+///
+/// returns: a new instance. Will never return NULL.
+///
+/// # Safety
+///
+/// The caller has to make sure that:
+///
+/// - the returned instance is freed in some way, either by using a consuming function or
+///   by explicitly calling `sp_connection_free`.
+#[no_mangle]
+pub unsafe extern "C" fn sp_connection_fake() -> NonNull<SPConnection> {
+    let result = Box::new(SPConnection(servicepoint::Connection::Fake));
+    NonNull::from(Box::leak(result))
+}
+
 /// Sends a [SPPacket] to the display using the [SPConnection].
 ///
 /// The passed `packet` gets consumed.

crates/servicepoint_binding_cs/ServicePoint/Connection.g.cs

@@ -37,6 +37,24 @@ namespace ServicePoint
             return native == null ? null : new Connection(native);
         }
 
+        /// <summary>
+        ///  Creates a new instance of [SPConnection] for testing that does not actually send anything.
+        ///
+        ///  returns: a new instance. Will never return NULL.
+        ///
+        ///  # Safety
+        ///
+        ///  The caller has to make sure that:
+        ///
+        ///  - the returned instance is freed in some way, either by using a consuming function or
+        ///    by explicitly calling `sp_connection_free`.
+        /// </summary>
+        [System.Runtime.CompilerServices.MethodImplAttribute(System.Runtime.CompilerServices.MethodImplOptions.AggressiveInlining)]
+        public static Connection Fake()
+        {
+            return new Connection(Connection.sp_connection_fake());
+        }
+
         /// <summary>
         ///  Sends a [SPPacket] to the display using the [SPConnection].
         ///
@@ -141,6 +159,9 @@ namespace ServicePoint
         [DllImport(__DllName, EntryPoint = "sp_connection_open", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
         private static extern SPConnection* sp_connection_open(byte* host);
 
+        [DllImport(__DllName, EntryPoint = "sp_connection_fake", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
+        private static extern SPConnection* sp_connection_fake();
+
         [DllImport(__DllName, EntryPoint = "sp_connection_send_packet", CallingConvention = CallingConvention.Cdecl, ExactSpelling = true)]
         [return: MarshalAs(UnmanagedType.U1)]
         private static extern bool sp_connection_send_packet(SPConnection* connection, SPPacket* packet);