refactor: This change adds two things:

- McpSessionManager constructor with McpTransportBuilder parameter.
- McpToolset new constructor to facilitate the creation of McpToolsets with injected McpSyncClient, so we can provide custom transport builder.

PiperOrigin-RevId: 785990204

Author: google-genai-bot

core/src/main/java/com/google/adk/tools/mcp/McpSessionManager.java

@@ -36,13 +36,20 @@ public class McpSessionManager {
 
   private final Object connectionParams; // ServerParameters or SseServerParameters
   private static final Logger logger = LoggerFactory.getLogger(McpSessionManager.class);
+  private final McpTransportBuilder transportBuilder;
 
   public McpSessionManager(Object connectionParams) {
     this.connectionParams = connectionParams;
+    this.transportBuilder = new DefaultMcpTransportBuilder();
+  }
+
+  public McpSessionManager(Object connectionParams, McpTransportBuilder transportBuilder) {
+    this.connectionParams = connectionParams;
+    this.transportBuilder = transportBuilder;
   }
 
   public McpSyncClient createSession() {
-    return initializeSession(this.connectionParams);
+    return initializeSession(this.connectionParams, this.transportBuilder);
   }
 
   public static McpSyncClient initializeSession(Object connectionParams) {

core/src/main/java/com/google/adk/tools/mcp/McpToolset.java

@@ -149,6 +149,26 @@ public McpToolset(ServerParameters connectionParams) {
     this(connectionParams, JsonBaseModel.getMapper(), Optional.empty());
   }
 
+  /**
+   * Initializes the McpToolset with a McpSyncClient and McpSessionManager.
+   *
+   * @param objectMapper An ObjectMapper instance for parsing schemas.
+   * @param toolFilter An Optional containing either a ToolPredicate or a List of tool names.
+   * @param mcpSession A McpSyncClient instance for testing.
+   * @param mcpSessionManager A McpSessionManager instance for testing.
+   */
+  public McpToolset(
+      ObjectMapper objectMapper,
+      Optional<Object> toolFilter,
+      McpSyncClient mcpSession,
+      McpSessionManager mcpSessionManager) {
+    Objects.requireNonNull(objectMapper);
+    this.objectMapper = objectMapper;
+    this.toolFilter = toolFilter;
+    this.mcpSession = mcpSession;
+    this.mcpSessionManager = mcpSessionManager;
+  }
+
   @Override
   public Flowable<BaseTool> getTools(ReadonlyContext readonlyContext) {
     return Flowable.fromCallable(