refactor: This change adds two things:

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

@@ -37,14 +37,20 @@
 public class McpSessionManager {
 
   private final Object connectionParams; // ServerParameters or SseServerParameters
+  private final McpTransportBuilder transportBuilder;
   private static final Logger logger = LoggerFactory.getLogger(McpSessionManager.class);
 
   public McpSessionManager(Object connectionParams) {
+    this(connectionParams, 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 +149,22 @@ public McpToolset(ServerParameters connectionParams) {
     this(connectionParams, JsonBaseModel.getMapper(), Optional.empty());
   }
 
+  /**
+   * Initializes the McpToolset with an McpSessionManager.
+   *
+   * @param mcpSessionManager A McpSessionManager instance for testing.
+   * @param objectMapper An ObjectMapper instance for parsing schemas.
+   * @param toolFilter An Optional containing either a ToolPredicate or a List of tool names.
+   */
+  public McpToolset(
+      McpSessionManager mcpSessionManager, ObjectMapper objectMapper, Optional<Object> toolFilter) {
+    Objects.requireNonNull(mcpSessionManager);
+    Objects.requireNonNull(objectMapper);
+    this.mcpSessionManager = mcpSessionManager;
+    this.objectMapper = objectMapper;
+    this.toolFilter = toolFilter;
+  }
+
   @Override
   public Flowable<BaseTool> getTools(ReadonlyContext readonlyContext) {
     return Flowable.fromCallable(