test(ios): reuse ResizingProcessor instead of a second transcoding mock

ios/Tests/GutenbergKitTests/Media/MediaUploadServerTests.swift

@@ -671,7 +671,7 @@ struct MediaUploadServerTests {
     // those reads: a file admitted for processing was forwarded unprocessed. The
     // host dropping it before the request is the same condition, deterministically.
     let mockUploader = MockInternalMediaClient()
-    var delegate: TranscodingProcessor? = TranscodingProcessor()
+    var delegate: ResizingProcessor? = ResizingProcessor()
     weak let weakDelegate = delegate
     let server = try await MediaUploadServer.start(processor: delegate, internalClient: mockUploader)
     defer { server.stop() }
@@ -1106,25 +1106,35 @@ private final class RecordingUploader: MediaUploader, @unchecked Sendable {
 
 /// An uploader whose delivery fails terminally, as one would after exhausting its own
 /// post-process recovery and force-deleting the orphan.
-private final class ThrowingUploader: MediaUploader, @unchecked Sendable {
+private final class ThrowingUploader: MediaUploader {
   struct Failure: Error {}
 
   func upload(_ upload: MediaUpload) async throws -> Data {
     throw Failure()
   }
 }
 
-/// A delegate that transcodes, used to check the server holds it across the whole
-/// request rather than re-reading a reference the host may have dropped.
-private final class TranscodingProcessor: MediaProcessor, @unchecked Sendable {
+/// A processor that declines every file by metadata.
+private final class DecliningProcessor: MediaProcessor {
   func handlesFile(ofType mimeType: String, named filename: String) -> Bool {
-    true
+    false
   }
+}
+
+private final class MockProcessor: MediaProcessor, @unchecked Sendable {
+  private let lock = NSLock()
+  private var _processFileCalled = false
+  private var _lastMimeType: String?
+
+  var processFileCalled: Bool { lock.withLock { _processFileCalled } }
+  var lastMimeType: String? { lock.withLock { _lastMimeType } }
 
   func processFile(at url: URL, mimeType: String, filename: String) async throws -> ProcessedProxyFile {
-    let processed = FileManager.default.temporaryDirectory.appendingPathComponent("clip.mp4")
-    try? Data("transcoded".utf8).write(to: processed)
-    return .processed(processed, mimeType: "video/mp4", filename: "clip.mp4")
+    lock.withLock {
+      _processFileCalled = true
+      _lastMimeType = mimeType
+    }
+    return .original
   }
 }