diff --git a/core/dialog.ts b/core/dialog.ts
index ade36aa25..7e2112985 100644
--- a/core/dialog.ts
+++ b/core/dialog.ts
@@ -6,6 +6,31 @@
 
 // Former goog.module ID: Blockly.dialog
 
+let alertImplementation = function (
+  message: string,
+  opt_callback?: () => void,
+) {
+  window.alert(message);
+  if (opt_callback) {
+    opt_callback();
+  }
+};
+
+let confirmImplementation = function (
+  message: string,
+  callback: (result: boolean) => void,
+) {
+  callback(window.confirm(message));
+};
+
+let promptImplementation = function (
+  message: string,
+  defaultValue: string,
+  callback: (result: string | null) => void,
+) {
+  callback(window.prompt(message, defaultValue));
+};
+
 /**
  * Wrapper to window.alert() that app developers may override via setAlert to
  * provide alternatives to the modal browser window.
@@ -13,12 +38,9 @@
  * @param message The message to display to the user.
  * @param opt_callback The callback when the alert is dismissed.
  */
-export let alert = (message: string, opt_callback?: () => void) => {
-  window.alert(message);
-  if (opt_callback) {
-    opt_callback();
-  }
-};
+export function alert(message: string, opt_callback?: () => void) {
+  alertImplementation(message, opt_callback);
+}
 
 /**
  * Sets the function to be run when Blockly.dialog.alert() is called.
@@ -26,10 +48,8 @@ export let alert = (message: string, opt_callback?: () => void) => {
  * @param alertFunction The function to be run.
  * @see Blockly.dialog.alert
  */
-export function setAlert(
-  alertFunction: (message: string, callback?: () => void) => void,
-) {
-  alert = alertFunction;
+export function setAlert(alertFunction: (p1: string, p2?: () => void) => void) {
+  alertImplementation = alertFunction;
 }
 
 /**
@@ -39,12 +59,16 @@ export function setAlert(
  * @param message The message to display to the user.
  * @param callback The callback for handling user response.
  */
-export let confirm = (
-  message: string,
-  callback: (confirmed: boolean) => void,
-) => {
-  callback(window.confirm(message));
-};
+export function confirm(message: string, callback: (p1: boolean) => void) {
+  TEST_ONLY.confirmInternal(message, callback);
+}
+
+/**
+ * Private version of confirm for stubbing in tests.
+ */
+function confirmInternal(message: string, callback: (p1: boolean) => void) {
+  confirmImplementation(message, callback);
+}
 
 /**
  * Sets the function to be run when Blockly.dialog.confirm() is called.
@@ -53,12 +77,9 @@ export let confirm = (
  * @see Blockly.dialog.confirm
  */
 export function setConfirm(
-  confirmFunction: (
-    message: string,
-    callback: (confirmed: boolean) => void,
-  ) => void,
+  confirmFunction: (p1: string, p2: (p1: boolean) => void) => void,
 ) {
-  confirm = confirmFunction;
+  confirmImplementation = confirmFunction;
 }
 
 /**
@@ -71,13 +92,13 @@ export function setConfirm(
  * @param defaultValue The value to initialize the prompt with.
  * @param callback The callback for handling user response.
  */
-export let prompt = (
+export function prompt(
   message: string,
   defaultValue: string,
-  callback: (userInput: string | null) => void,
-) => {
-  callback(window.prompt(message, defaultValue));
-};
+  callback: (p1: string | null) => void,
+) {
+  promptImplementation(message, defaultValue, callback);
+}
 
 /**
  * Sets the function to be run when Blockly.dialog.prompt() is called.
@@ -87,10 +108,14 @@ export let prompt = (
  */
 export function setPrompt(
   promptFunction: (
-    message: string,
-    defaultValue: string,
-    callback: (userInput: string | null) => void,
+    p1: string,
+    p2: string,
+    p3: (p1: string | null) => void,
   ) => void,
 ) {
-  prompt = promptFunction;
+  promptImplementation = promptFunction;
 }
+
+export const TEST_ONLY = {
+  confirmInternal,
+};
diff --git a/tests/mocha/contextmenu_items_test.js b/tests/mocha/contextmenu_items_test.js
index ef1a9530c..4596513c6 100644
--- a/tests/mocha/contextmenu_items_test.js
+++ b/tests/mocha/contextmenu_items_test.js
@@ -322,10 +322,10 @@ suite('Context Menu Items', function () {
       });
 
       test('Deletes all blocks after confirming', function () {
-        // Mocks the confirmation dialog and calls the callback with 'true'
-        // simulating ok.
-        const confirmStub = sinon.stub().callsArgWith(1, true);
-        Blockly.dialog.setConfirm(confirmStub);
+        // Mocks the confirmation dialog and calls the callback with 'true' simulating ok.
+        const confirmStub = sinon
+          .stub(Blockly.dialog.TEST_ONLY, 'confirmInternal')
+          .callsArgWith(1, true);
 
         this.workspace.newBlock('text');
         this.workspace.newBlock('text');
@@ -337,8 +337,9 @@ suite('Context Menu Items', function () {
 
       test('Does not delete blocks if not confirmed', function () {
         // Mocks the confirmation dialog and calls the callback with 'false' simulating cancel.
-        const confirmStub = sinon.stub().callsArgWith(1, false);
-        Blockly.dialog.setConfirm(confirmStub);
+        const confirmStub = sinon
+          .stub(Blockly.dialog.TEST_ONLY, 'confirmInternal')
+          .callsArgWith(1, false);
 
         this.workspace.newBlock('text');
         this.workspace.newBlock('text');
@@ -349,9 +350,10 @@ suite('Context Menu Items', function () {
       });
 
       test('No dialog for single block', function () {
-        const confirmStub = sinon.stub();
-        Blockly.dialog.setConfirm(confirmStub);
-
+        const confirmStub = sinon.stub(
+          Blockly.dialog.TEST_ONLY,
+          'confirmInternal',
+        );
         this.workspace.newBlock('text');
         this.deleteOption.callback(this.scope);
         this.clock.runAll();
diff --git a/tests/mocha/dialog_test.js b/tests/mocha/dialog_test.js
deleted file mode 100644
index 22831c58d..000000000
--- a/tests/mocha/dialog_test.js
+++ /dev/null
@@ -1,58 +0,0 @@
-/**
- * @license
- * Copyright 2024 Google LLC
- * SPDX-License-Identifier: Apache-2.0
- */
-
-suite.only('Dialog', function () {
-  teardown(function () {
-    sinon.restore();
-  });
-
-  suite('Prompt', function () {
-    test('setPrompt can take in a function with additional parameters', function () {
-      const spy = sinon.spy();
-      Blockly.dialog.setPrompt(spy);
-      const callback = () => {};
-
-      Blockly.dialog.prompt(
-        'message',
-        'defaultVal',
-        callback,
-        'extra parameter',
-      );
-
-      chai.assert.isTrue(
-        spy.calledWith('message', 'defaultVal', callback, 'extra parameter'),
-      );
-    });
-  });
-
-  suite('Confirm', function () {
-    test('setConfirm can take in a function with additional parameters', function () {
-      const spy = sinon.spy();
-      Blockly.dialog.setConfirm(spy);
-      const callback = () => {};
-
-      Blockly.dialog.confirm('message', callback, 'extra parameter');
-
-      chai.assert.isTrue(
-        spy.calledWith('message', callback, 'extra parameter'),
-      );
-    });
-  });
-
-  suite('Alert', function () {
-    test('setAlert can take in a function with additional parameters', function () {
-      const spy = sinon.spy();
-      Blockly.dialog.setAlert(spy);
-      const callback = () => {};
-
-      Blockly.dialog.alert('message', callback, 'extra parameter');
-
-      chai.assert.isTrue(
-        spy.calledWith('message', callback, 'extra parameter'),
-      );
-    });
-  });
-});
diff --git a/tests/mocha/index.html b/tests/mocha/index.html
index 34738605a..9c7b10cab 100644
--- a/tests/mocha/index.html
+++ b/tests/mocha/index.html
@@ -52,7 +52,6 @@
       import './contextmenu_items_test.js';
       import './contextmenu_test.js';
       import './cursor_test.js';
-      import './dialog_test.js';
       import './dropdowndiv_test.js';
       import './event_test.js';
       import './event_block_change_test.js';
diff --git a/tests/mocha/test_helpers/workspace.js b/tests/mocha/test_helpers/workspace.js
index ce8822019..6da113f8b 100644
--- a/tests/mocha/test_helpers/workspace.js
+++ b/tests/mocha/test_helpers/workspace.js
@@ -99,8 +99,9 @@ export function testAWorkspace() {
 
     test('deleteVariableById(id2) one usage', function () {
       // Deleting variable one usage should not trigger confirm dialog.
-      const stub = sinon.stub().callsArgWith(1, true);
-      Blockly.dialog.setConfirm(stub);
+      const stub = sinon
+        .stub(Blockly.dialog.TEST_ONLY, 'confirmInternal')
+        .callsArgWith(1, true);
       this.workspace.deleteVariableById('id2');
 
       sinon.assert.notCalled(stub);
@@ -112,8 +113,9 @@ export function testAWorkspace() {
 
     test('deleteVariableById(id1) multiple usages confirm', function () {
       // Deleting variable with multiple usages triggers confirm dialog.
-      const stub = sinon.stub().callsArgWith(1, true);
-      Blockly.dialog.setConfirm(stub);
+      const stub = sinon
+        .stub(Blockly.dialog.TEST_ONLY, 'confirmInternal')
+        .callsArgWith(1, true);
       this.workspace.deleteVariableById('id1');
 
       sinon.assert.calledOnce(stub);
@@ -125,8 +127,9 @@ export function testAWorkspace() {
 
     test('deleteVariableById(id1) multiple usages cancel', function () {
       // Deleting variable with multiple usages triggers confirm dialog.
-      const stub = sinon.stub().callsArgWith(1, false);
-      Blockly.dialog.setConfirm(stub);
+      const stub = sinon
+        .stub(Blockly.dialog.TEST_ONLY, 'confirmInternal')
+        .callsArgWith(1, false);
       this.workspace.deleteVariableById('id1');
 
       sinon.assert.calledOnce(stub);