diff --git a/lib/WebSocketConnection.js b/lib/WebSocketConnection.js
index 377118f0..62f42bb0 100644
--- a/lib/WebSocketConnection.js
+++ b/lib/WebSocketConnection.js
@@ -313,7 +313,10 @@ class WebSocketConnection extends EventEmitter {
       this.emit('error', error);
     }
     this.socket.destroy();
-    this._debug.printOutput();
+    // Only print debug output in non-test environments to avoid cluttering test output
+    if (process.env.NODE_ENV !== 'test') {
+      this._debug.printOutput();
+    }
   }
 
   handleSocketEnd() {
diff --git a/test/shared/setup.mjs b/test/shared/setup.mjs
index f00a742c..e316427d 100644
--- a/test/shared/setup.mjs
+++ b/test/shared/setup.mjs
@@ -1,23 +1,37 @@
 import { beforeEach, afterEach, vi } from 'vitest';
 import { stopAllServers } from '../helpers/test-server.mjs';
+import debug from 'debug';
 
 // Increase max listeners to avoid warnings when running many tests with child processes
 // Vitest adds exit/beforeExit listeners for each test file with spawned processes
 process.setMaxListeners(30);
 
+// Disable debug output during tests unless explicitly enabled
+if (!process.env.DEBUG) {
+  debug.disable();
+}
+
 // Global test setup for each test file
 beforeEach(() => {
   // Clear all mocks and timers
   vi.clearAllTimers();
   vi.clearAllMocks();
+
+  // Note: We don't disable debug in beforeEach as some tests need to enable it
+  // Tests that enable DEBUG should clean up properly in their own afterEach
 });
 
 afterEach(async () => {
   // Restore all mocks
   vi.restoreAllMocks();
-  
+
   // Clean up any test servers
   await stopAllServers();
+
+  // Re-disable debug after each test to prevent leakage
+  if (!process.env.DEBUG) {
+    debug.disable();
+  }
 });
 
 // Set up global test configuration
diff --git a/test/unit/core/utils-enhanced.test.mjs b/test/unit/core/utils-enhanced.test.mjs
index fbcbae37..f2ec89a9 100644
--- a/test/unit/core/utils-enhanced.test.mjs
+++ b/test/unit/core/utils-enhanced.test.mjs
@@ -9,6 +9,7 @@
  */
 import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
 import * as utils from '../../../lib/utils.js';
+import debug from 'debug';
 
 describe('Utils Module - Enhanced Coverage', () => {
   describe('BufferingLogger.printOutput() behavior', () => {
@@ -20,8 +21,12 @@ describe('Utils Module - Enhanced Coverage', () => {
     });
 
     afterEach(() => {
+      debug.disable();
       if (originalDebugEnv !== undefined) {
         process.env.DEBUG = originalDebugEnv;
+        if (originalDebugEnv) {
+          debug.enable(originalDebugEnv);
+        }
       } else {
         delete process.env.DEBUG;
       }
@@ -62,8 +67,12 @@ describe('Utils Module - Enhanced Coverage', () => {
     });
 
     afterEach(() => {
+      debug.disable();
       if (originalDebugEnv !== undefined) {
         process.env.DEBUG = originalDebugEnv;
+        if (originalDebugEnv) {
+          debug.enable(originalDebugEnv);
+        }
       } else {
         delete process.env.DEBUG;
       }
@@ -81,9 +90,12 @@ describe('Utils Module - Enhanced Coverage', () => {
 
         expect(mockLog).toHaveBeenCalled();
         // Verify the format includes timestamp and uniqueID
+        // printOutput calls logFunction.apply(global, args) where args includes:
+        // [formatString, date, uniqueID, ...originalArgs]
         const firstCall = mockLog.mock.calls[0];
         expect(firstCall).toBeDefined();
-        expect(firstCall[0]).toContain('test-id');
+        // The uniqueID should be in args[2] (after formatString and date)
+        expect(firstCall[2]).toBe('test-id');
       }
     });
 
diff --git a/test/unit/core/utils.test.mjs b/test/unit/core/utils.test.mjs
index 91271ce2..79175d10 100644
--- a/test/unit/core/utils.test.mjs
+++ b/test/unit/core/utils.test.mjs
@@ -11,6 +11,7 @@
 import { describe, it, expect, beforeEach, afterEach, vi } from 'vitest';
 import { EventEmitter } from 'events';
 import * as utils from '../../../lib/utils.js';
+import debug from 'debug';
 
 describe('Utils Module', () => {
   describe('noop()', () => {
@@ -251,8 +252,12 @@ describe('Utils Module', () => {
     });
 
     afterEach(() => {
+      debug.disable();
       if (originalDebugEnv !== undefined) {
         process.env.DEBUG = originalDebugEnv;
+        if (originalDebugEnv) {
+          debug.enable(originalDebugEnv);
+        }
       } else {
         delete process.env.DEBUG;
       }