[JExtract/FFM] Add Data and DataProtocol tests

Also, run Samples:SwiftKitSampleApp:test in CI

Author: rintaro

Samples/SwiftKitSampleApp/Sources/MySwiftLibrary/MySwiftLibrary.swift

@@ -63,8 +63,9 @@ public func withBuffer(body: (UnsafeRawBufferPointer) -> Void) {
   body(globalBuffer)
 }
 
-public func globalReceiveSomeDataProtocol(data: some DataProtocol) {
+public func globalReceiveSomeDataProtocol(data: some DataProtocol) -> Int {
   p(Array(data).description)
+  return data.count
 }
 
 // ==== Internal helpers

Samples/SwiftKitSampleApp/ci-validate.sh

@@ -3,4 +3,5 @@
 set -x
 set -e
 
-./gradlew run
+./gradlew run
+./gradlew test

Samples/SwiftKitSampleApp/src/test/java/com/example/swift/DataImportTest.java

@@ -0,0 +1,49 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
+package com.example.swift;
+
+import org.junit.jupiter.api.Test;
+import org.swift.swiftkit.ffm.AllocatingSwiftArena;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class DataImportTest {
+    @Test
+    void test_Data_receiveAndReturn() {
+        try (var arena = AllocatingSwiftArena.ofConfined()) {
+            var origBytes = arena.allocateFrom("foobar");
+            var origDat = Data.init(origBytes, origBytes.byteSize(), arena);
+            assertEquals(7, origDat.getCount());
+
+            var retDat = MySwiftLibrary.globalReceiveReturnData(origDat, arena);
+            assertEquals(7, retDat.getCount());
+            retDat.withUnsafeBytes((retBytes) -> {
+                assertEquals(7, retBytes.byteSize());
+                var str = retBytes.getString(0);
+                assertEquals("foobar", str);
+            });
+        }
+    }
+
+    @Test
+    void test_DataProtocol_receive() {
+        try (var arena = AllocatingSwiftArena.ofConfined()) {
+            var bytes = arena.allocateFrom("hello");
+            var dat = Data.init(bytes, bytes.byteSize(), arena);
+            var result = MySwiftLibrary.globalReceiveSomeDataProtocol(dat);
+            assertEquals(6, result);
+        }
+    }
+}