diff --git a/tests/deps.mocha.js b/tests/deps.mocha.js
index f2d550157d9..c43d84e13a5 100644
--- a/tests/deps.mocha.js
+++ b/tests/deps.mocha.js
@@ -44,19 +44,19 @@ goog.addDependency('../../tests/mocha/registry_test.js', ['Blockly.test.registry
 goog.addDependency('../../tests/mocha/run_mocha_tests_in_browser.js', [], [], {'lang': 'es8'});
 goog.addDependency('../../tests/mocha/serializer_test.js', ['Blockly.test.serialization'], ['Blockly.test.helpers.common', 'Blockly.test.helpers.setupTeardown'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/shortcut_registry_test.js', ['Blockly.test.shortcutRegistry'], ['Blockly.test.helpers.setupTeardown', 'Blockly.test.helpers.userInput'], {'lang': 'es6', 'module': 'goog'});
-goog.addDependency('../../tests/mocha/test_helpers/block_definitions.js', ['Blockly.test.helpers.blockDefinitions'], [], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/code_generation.js', ['Blockly.test.helpers.codeGeneration'], ['Blockly.test.helpers.common'], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/common.js', ['Blockly.test.helpers.common'], [], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/events.js', ['Blockly.test.helpers.events'], [], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/fields.js', ['Blockly.test.helpers.fields'], ['Blockly.test.helpers.common'], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/procedures.js', ['Blockly.test.helpers.procedures'], ['Blockly.ConnectionType'], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/serialization.js', ['Blockly.test.helpers.serialization'], ['Blockly.test.helpers.common'], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/setup_teardown.js', ['Blockly.test.helpers.setupTeardown'], ['Blockly.Events.utils', 'Blockly.blocks'], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/toolbox_definitions.js', ['Blockly.test.helpers.toolboxDefinitions'], [], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/user_input.js', ['Blockly.test.helpers.userInput'], ['Blockly.utils.KeyCodes'], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/variables.js', ['Blockly.test.helpers.variables'], [], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/warnings.js', ['Blockly.test.helpers.warnings'], [], {'lang': 'es6', 'module': 'es6'});
-goog.addDependency('../../tests/mocha/test_helpers/workspace.js', ['Blockly.test.helpers.workspace'], ['Blockly.Events.utils', 'Blockly.test.helpers.setupTeardown', 'Blockly.test.helpers.variables', 'Blockly.test.helpers.warnings'], {'lang': 'es6', 'module': 'es6'});
+goog.addDependency('../../tests/mocha/test_helpers/block_definitions.js', ['Blockly.test.helpers.blockDefinitions'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/code_generation.js', ['Blockly.test.helpers.codeGeneration'], ['Blockly.test.helpers.common'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/common.js', ['Blockly.test.helpers.common'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/events.js', ['Blockly.test.helpers.events'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/fields.js', ['Blockly.test.helpers.fields'], ['Blockly.test.helpers.common'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/procedures.js', ['Blockly.test.helpers.procedures'], ['Blockly.ConnectionType'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/serialization.js', ['Blockly.test.helpers.serialization'], ['Blockly.test.helpers.common'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/setup_teardown.js', ['Blockly.test.helpers.setupTeardown'], ['Blockly.Events.utils', 'Blockly.blocks'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/toolbox_definitions.js', ['Blockly.test.helpers.toolboxDefinitions'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/user_input.js', ['Blockly.test.helpers.userInput'], ['Blockly.utils.KeyCodes'], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/variables.js', ['Blockly.test.helpers.variables'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/warnings.js', ['Blockly.test.helpers.warnings'], [], {'lang': 'es6', 'module': 'goog'});
+goog.addDependency('../../tests/mocha/test_helpers/workspace.js', ['Blockly.test.helpers.workspace'], ['Blockly.Events.utils', 'Blockly.test.helpers.setupTeardown', 'Blockly.test.helpers.variables', 'Blockly.test.helpers.warnings'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/theme_test.js', ['Blockly.test.theme'], ['Blockly.Events.utils', 'Blockly.test.helpers.events', 'Blockly.test.helpers.setupTeardown'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/toolbox_test.js', ['Blockly.test.toolbox'], ['Blockly.test.helpers.blockDefinitions', 'Blockly.test.helpers.setupTeardown', 'Blockly.test.helpers.toolboxDefinitions'], {'lang': 'es6', 'module': 'goog'});
 goog.addDependency('../../tests/mocha/tooltip_test.js', ['Blockly.test.tooltip'], ['Blockly.test.helpers.setupTeardown'], {'lang': 'es6', 'module': 'goog'});
diff --git a/tests/mocha/.eslintrc.json b/tests/mocha/.eslintrc.json
index bf87ec0bd20..8ebf31ae61c 100644
--- a/tests/mocha/.eslintrc.json
+++ b/tests/mocha/.eslintrc.json
@@ -1,7 +1,4 @@
 {
-    "parserOptions": {
-      "sourceType": "module"
-    },
     "env": {
         "browser": true,
         "mocha": true
@@ -14,8 +11,7 @@
         "no-unused-vars": ["off"],
         // Allow uncommented helper functions in tests.
         "require-jsdoc": ["off"],
-        "prefer-rest-params": ["off"],
-        "no-invalid-this": ["off"]
+        "prefer-rest-params": ["off"]
     },
     "extends": "../../.eslintrc.json"
 }
diff --git a/tests/mocha/astnode_test.js b/tests/mocha/astnode_test.js
index 1a15dfb6244..f974f3ea8a2 100644
--- a/tests/mocha/astnode_test.js
+++ b/tests/mocha/astnode_test.js
@@ -11,7 +11,6 @@ const {sharedTestSetup, sharedTestTeardown, workspaceTeardown} = goog.require('B
 
 
 suite('ASTNode', function() {
-  console.log('1/a');
   setup(function() {
     sharedTestSetup.call(this);
     Blockly.defineBlocksWithJsonArray([{
@@ -101,9 +100,7 @@ suite('ASTNode', function() {
   });
 
   suite('HelperFunctions', function() {
-    console.log('2');
     test('findNextForInput_', function() {
-      console.log('3');
       const input = this.blocks.statementInput1.inputList[0];
       const input2 = this.blocks.statementInput1.inputList[1];
       const connection = input.connection;
@@ -172,7 +169,6 @@ suite('ASTNode', function() {
   });
 
   suite('NavigationFunctions', function() {
-    console.log('b');
     setup(function() {
       Blockly.defineBlocksWithJsonArray([{
         "type": "top_connection",
@@ -323,9 +319,7 @@ suite('ASTNode', function() {
         workspaceTeardown.call(this, this.singleBlockWorkspace);
       });
 
-      console.log('c');
       test('fromPreviousToBlock', function() {
-        console.log('d');
         const prevConnection = this.blocks.statementInput1.previousConnection;
         const node = ASTNode.createConnectionNode(prevConnection);
         const nextNode = node.next();
diff --git a/tests/mocha/index.html b/tests/mocha/index.html
index 694d5215aac..3d1cfaa9cde 100644
--- a/tests/mocha/index.html
+++ b/tests/mocha/index.html
@@ -172,7 +172,7 @@
       <block type="test_field_block"></block>
     </xml>
 
-    <script type="module">
+    <script>
       let runner = mocha.run(function(failures) {
         var failureDiv = document.getElementById('failureCount');
         failureDiv.setAttribute('tests_failed', failures);
diff --git a/tests/mocha/test_helpers/block_definitions.js b/tests/mocha/test_helpers/block_definitions.js
index 213075a74fe..a30d7defe91 100644
--- a/tests/mocha/test_helpers/block_definitions.js
+++ b/tests/mocha/test_helpers/block_definitions.js
@@ -4,10 +4,10 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.blockDefinitions');
+goog.module('Blockly.test.helpers.blockDefinitions');
 
 
-export function defineStackBlock(name = 'stack_block') {
+function defineStackBlock(name = 'stack_block') {
   Blockly.defineBlocksWithJsonArray([{
     "type": name,
     "message0": "",
@@ -15,8 +15,9 @@ export function defineStackBlock(name = 'stack_block') {
     "nextStatement": null,
   }]);
 }
+exports.defineStackBlock = defineStackBlock;
 
-export function defineRowBlock(name = 'row_block') {
+function defineRowBlock(name = 'row_block') {
   Blockly.defineBlocksWithJsonArray([{
     "type": name,
     "message0": "%1",
@@ -29,8 +30,9 @@ export function defineRowBlock(name = 'row_block') {
     "output": null,
   }]);
 }
+exports.defineRowBlock = defineRowBlock;
 
-export function defineStatementBlock(name = 'statement_block') {
+function defineStatementBlock(name = 'statement_block') {
   Blockly.defineBlocksWithJsonArray([{
     "type": name,
     "message0": "%1",
@@ -47,8 +49,9 @@ export function defineStatementBlock(name = 'statement_block') {
     "helpUrl": "",
   }]);
 }
+exports.defineStatementBlock = defineStatementBlock;
 
-export function defineBasicBlockWithField(name = 'test_field_block') {
+function defineBasicBlockWithField(name = 'test_field_block') {
   Blockly.defineBlocksWithJsonArray([{
     "type": name,
     "message0": "%1",
@@ -61,8 +64,9 @@ export function defineBasicBlockWithField(name = 'test_field_block') {
     "output": null,
   }]);
 }
+exports.defineBasicBlockWithField = defineBasicBlockWithField;
 
-export function defineMutatorBlocks() {
+function defineMutatorBlocks() {
   Blockly.defineBlocksWithJsonArray([
     {
       'type': 'xml_block',
@@ -154,8 +158,9 @@ export function defineMutatorBlocks() {
   };
   Blockly.Extensions.registerMutator('jso_mutator', jsoMutator);
 }
+exports.defineMutatorBlocks = defineMutatorBlocks;
 
-export function createTestBlock() {
+function createTestBlock() {
   return {
     'id': 'test',
     'rendered': false,
@@ -169,10 +174,12 @@ export function createTestBlock() {
     'updateVarName': Blockly.Block.prototype.updateVarName,
   };
 }
+exports.createTestBlock = createTestBlock;
 
-export function createRenderedBlock(workspaceSvg, type) {
+function createRenderedBlock(workspaceSvg, type) {
   const block = workspaceSvg.newBlock(type);
   block.initSvg();
   block.render();
   return block;
 }
+exports.createRenderedBlock = createRenderedBlock;
diff --git a/tests/mocha/test_helpers/code_generation.js b/tests/mocha/test_helpers/code_generation.js
index 4d3c0a375e1..72d520c7f98 100644
--- a/tests/mocha/test_helpers/code_generation.js
+++ b/tests/mocha/test_helpers/code_generation.js
@@ -5,7 +5,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.codeGeneration');
+goog.module('Blockly.test.helpers.codeGeneration');
 
 const {runTestSuites} = goog.require('Blockly.test.helpers.common');
 
@@ -15,7 +15,7 @@ const {runTestSuites} = goog.require('Blockly.test.helpers.common');
  * @implements {TestCase}
  * @record
  */
-export class CodeGenerationTestCase {
+class CodeGenerationTestCase {
   /**
    * Class for a code generation test case.
    */
@@ -43,13 +43,14 @@ export class CodeGenerationTestCase {
    */
   createBlock(workspace) {}
 }
+exports.CodeGenerationTestCase = CodeGenerationTestCase;
 
 /**
  * Code generation test suite.
  * @extends {TestSuite<CodeGenerationTestCase, CodeGenerationTestSuite>}
  * @record
  */
-export class CodeGenerationTestSuite {
+class CodeGenerationTestSuite {
   /**
    * Class for a code generation test suite.
    */
@@ -60,6 +61,7 @@ export class CodeGenerationTestSuite {
     this.generator;
   }
 }
+exports.CodeGenerationTestSuite = CodeGenerationTestSuite;
 
 /**
  * Returns mocha test callback for code generation based on provided
@@ -100,7 +102,7 @@ const createCodeGenerationTestFn_ = (generator) => {
  * Runs blockToCode test suites.
  * @param {!Array<!CodeGenerationTestSuite>} testSuites The test suites to run.
  */
-export const runCodeGenerationTestSuites = (testSuites) => {
+const runCodeGenerationTestSuites = (testSuites) => {
   /**
    * Creates function used to generate mocha test callback.
    * @param {!CodeGenerationTestSuite} suiteInfo The test suite information.
@@ -113,3 +115,4 @@ export const runCodeGenerationTestSuites = (testSuites) => {
 
   runTestSuites(testSuites, createTestFn);
 };
+exports.runCodeGenerationTestSuites = runCodeGenerationTestSuites;
diff --git a/tests/mocha/test_helpers/common.js b/tests/mocha/test_helpers/common.js
index 8e705b0fc0d..fcb61021a64 100644
--- a/tests/mocha/test_helpers/common.js
+++ b/tests/mocha/test_helpers/common.js
@@ -4,13 +4,13 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.common');
+goog.module('Blockly.test.helpers.common');
 
 /**
  * Test case configuration.
  * @record
  */
-export class TestCase {
+class TestCase {
   /**
    * Class for a test case configuration.
    */
@@ -31,6 +31,7 @@ export class TestCase {
     this.only;
   }
 }
+exports.TestCase = TestCase;
 
 /**
  * Test suite configuration.
@@ -38,7 +39,7 @@ export class TestCase {
  * @template {TestCase} T
  * @template {TestSuite} U
  */
-export class TestSuite {
+class TestSuite {
   /**
    * Class for a test suite configuration.
    */
@@ -67,6 +68,7 @@ export class TestSuite {
     this.only;
   }
 }
+exports.TestSuite = TestSuite;
 
 /**
  * Runs provided test cases.
@@ -75,13 +77,14 @@ export class TestSuite {
  * @param {function(T):Function} createTestCallback Creates test
  *    callback using given test case.
  */
-export function runTestCases(testCases, createTestCallback) {
+function runTestCases(testCases, createTestCallback) {
   testCases.forEach((testCase) => {
     let testCall = (testCase.skip ? test.skip : test);
     testCall = (testCase.only ? test.only : testCall);
     testCall(testCase.title, createTestCallback(testCase));
   });
 }
+exports.runTestCases = runTestCases;
 
 /**
  * Runs provided test suite.
@@ -92,7 +95,7 @@ export function runTestCases(testCases, createTestCallback) {
  *    } createTestCaseCallback Creates test case callback using given test
  *    suite.
  */
-export function runTestSuites(testSuites, createTestCaseCallback) {
+function runTestSuites(testSuites, createTestCaseCallback) {
   testSuites.forEach((testSuite) => {
     let suiteCall = (testSuite.skip ? suite.skip : suite);
     suiteCall = (testSuite.only ? suite.only : suiteCall);
@@ -106,3 +109,4 @@ export function runTestSuites(testSuites, createTestCaseCallback) {
     });
   });
 }
+exports.runTestSuites = runTestSuites;
diff --git a/tests/mocha/test_helpers/events.js b/tests/mocha/test_helpers/events.js
index ba1b3f4f81f..e69573318d1 100644
--- a/tests/mocha/test_helpers/events.js
+++ b/tests/mocha/test_helpers/events.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.events');
+goog.module('Blockly.test.helpers.events');
 
 
 /**
@@ -13,9 +13,10 @@ goog.declareModuleId('Blockly.test.helpers.events');
  *    calls on.
  * @return {!SinonSpy} The created spy.
  */
-export function createFireChangeListenerSpy(workspace) {
+function createFireChangeListenerSpy(workspace) {
   return sinon.spy(workspace, 'fireChangeListener');
 }
+exports.createFireChangeListenerSpy = createFireChangeListenerSpy;
 
 /**
  * Asserts whether the given xml property has the expected property.
@@ -74,7 +75,7 @@ function isXmlProperty_(key) {
  * @param {boolean=} [isUiEvent=false] Whether the event is a UI event.
  * @param {string=} message Optional message to prepend assert messages.
  */
-export function assertEventEquals(event, expectedType,
+function assertEventEquals(event, expectedType,
     expectedWorkspaceId, expectedBlockId, expectedProperties, isUiEvent = false, message) {
   let prependMessage = message ? message + ' ' : '';
   prependMessage += 'Event fired ';
@@ -106,6 +107,7 @@ export function assertEventEquals(event, expectedType,
     chai.assert.isFalse(event.isUiEvent);
   }
 }
+exports.assertEventEquals = assertEventEquals;
 
 /**
  * Asserts that an event with the given values was fired.
@@ -117,7 +119,7 @@ export function assertEventEquals(event, expectedType,
  * @param {string} expectedWorkspaceId Expected workspace id of event fired.
  * @param {?string=} expectedBlockId Expected block id of event fired.
  */
-export function assertEventFired(spy, instanceType, expectedProperties,
+function assertEventFired(spy, instanceType, expectedProperties,
     expectedWorkspaceId, expectedBlockId) {
   expectedProperties = Object.assign({
     workspaceId: expectedWorkspaceId,
@@ -127,6 +129,7 @@ export function assertEventFired(spy, instanceType, expectedProperties,
       sinon.match.instanceOf(instanceType).and(sinon.match(expectedProperties));
   sinon.assert.calledWith(spy, expectedEvent);
 }
+exports.assertEventFired = assertEventFired;
 
 /**
  * Asserts that an event with the given values was not fired.
@@ -138,7 +141,7 @@ export function assertEventFired(spy, instanceType, expectedProperties,
  * @param {string=} expectedWorkspaceId Expected workspace id of event fired.
  * @param {?string=} expectedBlockId Expected block id of event fired.
  */
-export function assertEventNotFired(spy, instanceType, expectedProperties,
+function assertEventNotFired(spy, instanceType, expectedProperties,
     expectedWorkspaceId, expectedBlockId) {
   expectedProperties.type = instanceType.prototype.type;
   if (expectedWorkspaceId !== undefined) {
@@ -151,6 +154,7 @@ export function assertEventNotFired(spy, instanceType, expectedProperties,
       sinon.match.instanceOf(instanceType).and(sinon.match(expectedProperties));
   sinon.assert.neverCalledWith(spy, expectedEvent);
 }
+exports.assertEventNotFired = assertEventNotFired;
 
 /**
  * Filters out xml properties from given object based on key.
@@ -185,7 +189,7 @@ function splitByXmlProperties_(properties) {
  * @param {string} expectedWorkspaceId Expected workspace id of event fired.
  * @param {?string=} expectedBlockId Expected block id of event fired.
  */
-export function assertNthCallEventArgEquals(spy, n, instanceType, expectedProperties,
+function assertNthCallEventArgEquals(spy, n, instanceType, expectedProperties,
     expectedWorkspaceId, expectedBlockId) {
   const nthCall = spy.getCall(n);
   const splitProperties = splitByXmlProperties_(expectedProperties);
@@ -197,3 +201,4 @@ export function assertNthCallEventArgEquals(spy, n, instanceType, expectedProper
   const eventArg = nthCall.firstArg;
   assertXmlProperties_(eventArg, xmlProperties);
 }
+exports.assertNthCallEventArgEquals = assertNthCallEventArgEquals;
diff --git a/tests/mocha/test_helpers/fields.js b/tests/mocha/test_helpers/fields.js
index ce69e2eb336..dd89e55fa35 100644
--- a/tests/mocha/test_helpers/fields.js
+++ b/tests/mocha/test_helpers/fields.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.fields');
+goog.module('Blockly.test.helpers.fields');
 
 const {runTestCases, TestCase} = goog.require('Blockly.test.helpers.common');
 
@@ -14,7 +14,7 @@ const {runTestCases, TestCase} = goog.require('Blockly.test.helpers.common');
  * @implements {TestCase}
  * @record
  */
-export class FieldValueTestCase {
+class FieldValueTestCase {
   /**
    * Class for a a field value test case.
    */
@@ -39,13 +39,14 @@ export class FieldValueTestCase {
     this.errMsgMatcher;
   }
 }
+exports.FieldValueTestCase = FieldValueTestCase;
 
 /**
  * Field creation test case.
  * @extends {FieldValueTestCase}
  * @record
  */
-export class FieldCreationTestCase {
+class FieldCreationTestCase {
   /**
    * Class for a field creation test case.
    */
@@ -60,6 +61,7 @@ export class FieldCreationTestCase {
     this.json;
   }
 }
+exports.FieldCreationTestCase = FieldCreationTestCase;
 
 /**
  * Assert a field's value is the same as the expected value.
@@ -67,7 +69,7 @@ export class FieldCreationTestCase {
  * @param {*} expectedValue The expected value.
  * @param {string=} expectedText The expected text.
  */
-export function assertFieldValue(field, expectedValue, expectedText = undefined) {
+function assertFieldValue(field, expectedValue, expectedText = undefined) {
   const actualValue = field.getValue();
   const actualText = field.getText();
   if (expectedText === undefined) {
@@ -76,6 +78,7 @@ export function assertFieldValue(field, expectedValue, expectedText = undefined)
   chai.assert.equal(actualValue, expectedValue, 'Value');
   chai.assert.equal(actualText, expectedText, 'Text');
 }
+exports.assertFieldValue = assertFieldValue;
 
 /**
  * Runs provided creation test cases.
@@ -142,7 +145,7 @@ function runCreationTestsAssertThrows_(testCases, creation) {
  * @param {function(!FieldCreationTestCase=)=} customCreateWithJs Custom
  *    creation function to use in tests.
  */
-export function runConstructorSuiteTests(TestedField, validValueTestCases,
+function runConstructorSuiteTests(TestedField, validValueTestCases,
     invalidValueTestCases, validRunAssertField, assertFieldDefault,
     customCreateWithJs) {
   suite('Constructor', function() {
@@ -179,6 +182,7 @@ export function runConstructorSuiteTests(TestedField, validValueTestCases,
     runCreationTests_(validValueTestCases, validRunAssertField, createWithJs);
   });
 }
+exports.runConstructorSuiteTests = runConstructorSuiteTests;
 
 /**
  * Runs suite of tests for fromJson creation of specified field.
@@ -196,7 +200,7 @@ export function runConstructorSuiteTests(TestedField, validValueTestCases,
  * @param {function(!FieldCreationTestCase=)=} customCreateWithJson Custom
  *    creation function to use in tests.
  */
-export function runFromJsonSuiteTests(TestedField, validValueTestCases,
+function runFromJsonSuiteTests(TestedField, validValueTestCases,
     invalidValueTestCases, validRunAssertField, assertFieldDefault,
     customCreateWithJson) {
   suite('fromJson', function() {
@@ -233,6 +237,7 @@ export function runFromJsonSuiteTests(TestedField, validValueTestCases,
     runCreationTests_(validValueTestCases, validRunAssertField, createWithJson);
   });
 }
+exports.runFromJsonSuiteTests = runFromJsonSuiteTests;
 
 /**
  * Runs tests for setValue calls.
@@ -245,7 +250,7 @@ export function runFromJsonSuiteTests(TestedField, validValueTestCases,
  * @param {string=} invalidRunExpectedText Expected text for field after invalid
  *    call to setValue.
  */
-export function runSetValueTests(validValueTestCases, invalidValueTestCases,
+function runSetValueTests(validValueTestCases, invalidValueTestCases,
     invalidRunExpectedValue, invalidRunExpectedText) {
   /**
    * Creates test callback for invalid setValue test.
@@ -274,3 +279,4 @@ export function runSetValueTests(validValueTestCases, invalidValueTestCases,
   runTestCases(invalidValueTestCases, createInvalidSetValueTestCallback);
   runTestCases(validValueTestCases, createValidSetValueTestCallback);
 }
+exports.runSetValueTests = runSetValueTests;
diff --git a/tests/mocha/test_helpers/procedures.js b/tests/mocha/test_helpers/procedures.js
index 68c7f2f3de8..6978e283eb9 100644
--- a/tests/mocha/test_helpers/procedures.js
+++ b/tests/mocha/test_helpers/procedures.js
@@ -3,7 +3,7 @@
  * Copyright 2020 Google LLC
  * SPDX-License-Identifier: Apache-2.0
  */
-goog.declareModuleId('Blockly.test.helpers.procedures');
+goog.module('Blockly.test.helpers.procedures');
 
 const {ConnectionType} = goog.require('Blockly.ConnectionType');
 
@@ -55,7 +55,7 @@ function assertCallBlockArgsStructure(callBlock, args) {
  * @param {boolean=} hasStatements If we expect the procedure def to have a
  *     statement input or not.
  */
-export function assertDefBlockStructure(defBlock, hasReturn = false,
+function assertDefBlockStructure(defBlock, hasReturn = false,
     args = [], varIds = [], hasStatements = true) {
   if (hasStatements) {
     chai.assert.isNotNull(defBlock.getInput('STACK'),
@@ -82,6 +82,7 @@ export function assertDefBlockStructure(defBlock, hasReturn = false,
   chai.assert.sameOrderedMembers(defBlock.getVars(), args);
   assertBlockVarModels(defBlock, varIds);
 }
+exports.assertDefBlockStructure = assertDefBlockStructure;
 
 /**
  * Asserts that the procedure definition block has the expected inputs and
@@ -90,7 +91,7 @@ export function assertDefBlockStructure(defBlock, hasReturn = false,
  * @param {Array<string>=} args An array of argument names.
  * @param {Array<string>=} varIds An array of variable ids.
  */
-export function assertCallBlockStructure(callBlock, args = [], varIds = []) {
+function assertCallBlockStructure(callBlock, args = [], varIds = []) {
   if (args.length) {
     chai.assert.include(callBlock.toString(), 'with');
   } else {
@@ -100,6 +101,7 @@ export function assertCallBlockStructure(callBlock, args = [], varIds = []) {
   assertCallBlockArgsStructure(callBlock, args);
   assertBlockVarModels(callBlock, varIds);
 }
+exports.assertCallBlockStructure = assertCallBlockStructure;
 
 /**
  * Creates procedure definition block using domToBlock call.
@@ -109,7 +111,7 @@ export function assertCallBlockStructure(callBlock, args = [], varIds = []) {
  * @param {Array<string>=} args An array of argument names.
  * @return {Blockly.Block} The created block.
  */
-export function createProcDefBlock(
+function createProcDefBlock(
     workspace, hasReturn = false, args = []) {
   const type = hasReturn ?
       'procedures_defreturn' : 'procedures_defnoreturn';
@@ -123,6 +125,7 @@ export function createProcDefBlock(
       '</block>';
   return Blockly.Xml.domToBlock(Blockly.Xml.textToDom(xml), workspace);
 }
+exports.createProcDefBlock = createProcDefBlock;
 
 /**
  * Creates procedure call block using domToBlock call.
@@ -131,7 +134,7 @@ export function createProcDefBlock(
  *    has return.
  * @return {Blockly.Block} The created block.
  */
-export function createProcCallBlock(
+function createProcCallBlock(
     workspace, hasReturn = false) {
   const type = hasReturn ?
       'procedures_callreturn' : 'procedures_callnoreturn';
@@ -141,3 +144,4 @@ export function createProcCallBlock(
       '</block>'
   ), workspace);
 }
+exports.createProcCallBlock = createProcCallBlock;
diff --git a/tests/mocha/test_helpers/serialization.js b/tests/mocha/test_helpers/serialization.js
index 8aa4cc1f06d..c8b90ba7f16 100644
--- a/tests/mocha/test_helpers/serialization.js
+++ b/tests/mocha/test_helpers/serialization.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.serialization');
+goog.module('Blockly.test.helpers.serialization');
 
 const {runTestCases} = goog.require('Blockly.test.helpers.common');
 
@@ -13,7 +13,7 @@ const {runTestCases} = goog.require('Blockly.test.helpers.common');
  * @implements {TestCase}
  * @record
  */
-export class SerializationTestCase {
+class SerializationTestCase {
   /**
    * Class for a block serialization test case.
    */
@@ -45,12 +45,13 @@ export class SerializationTestCase {
    */
   assertBlockStructure(block) {}
 }
+exports.SerializationTestCase = SerializationTestCase;
 
 /**
  * Runs serialization test suite.
  * @param {!Array<!SerializationTestCase>} testCases The test cases to run.
  */
-export const runSerializationTestSuite = (testCases) => {
+const runSerializationTestSuite = (testCases) => {
   /**
    * Creates test callback for xmlToBlock test.
    * @param {!SerializationTestCase} testCase The test case information.
@@ -128,3 +129,4 @@ export const runSerializationTestSuite = (testCases) => {
     });
   });
 };
+exports.runSerializationTestSuite = runSerializationTestSuite;
diff --git a/tests/mocha/test_helpers/setup_teardown.js b/tests/mocha/test_helpers/setup_teardown.js
index 3b66f7a9ab0..e1b085be15b 100644
--- a/tests/mocha/test_helpers/setup_teardown.js
+++ b/tests/mocha/test_helpers/setup_teardown.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.setupTeardown');
+goog.module('Blockly.test.helpers.setupTeardown');
 
 const eventUtils = goog.require('Blockly.Events.utils');
 const {Blocks} = goog.require('Blockly.blocks');
@@ -16,7 +16,7 @@ const {Blocks} = goog.require('Blockly.blocks');
  * using workspaceTeardown.call(this).
  * @param {!Blockly.Workspace} workspace The workspace to dispose.
  */
-export function workspaceTeardown(workspace) {
+function workspaceTeardown(workspace) {
   try {
     this.clock.runAll();  // Run all queued setTimeout calls.
     workspace.dispose();
@@ -26,6 +26,7 @@ export function workspaceTeardown(workspace) {
     console.error(testRef.fullTitle() + '\n', e);
   }
 }
+exports.workspaceTeardown = workspaceTeardown;
 
 /**
  * Creates stub for Blockly.Events.fire that advances the clock forward after
@@ -52,9 +53,10 @@ function createEventsFireStubFireImmediately_(clock) {
  *    sharedTestSetup.
  * @param {string} message The message to add to shared cleanup object.
  */
-export function addMessageToCleanup(sharedCleanupObj, message) {
+function addMessageToCleanup(sharedCleanupObj, message) {
   sharedCleanupObj.messagesCleanup_.push(message);
 }
+exports.addMessageToCleanup = addMessageToCleanup;
 
 /**
  * Adds block type to shared cleanup object so that it is cleaned from
@@ -63,9 +65,10 @@ export function addMessageToCleanup(sharedCleanupObj, message) {
  *    sharedTestSetup.
  * @param {string} blockType The block type to add to shared cleanup object.
  */
-export function addBlockTypeToCleanup(sharedCleanupObj, blockType) {
+function addBlockTypeToCleanup(sharedCleanupObj, blockType) {
   sharedCleanupObj.blockTypesCleanup_.push(blockType);
 }
+exports.addBlockTypeToCleanup = addBlockTypeToCleanup;
 
 /**
  * Wraps Blockly.defineBlocksWithJsonArray using stub in order to keep track of
@@ -108,7 +111,7 @@ function wrapDefineBlocksWithJsonArrayWithCleanup_(sharedCleanupObj) {
  * @param {Object<string, boolean>} options Options to enable/disable setup
  *    of certain stubs.
  */
-export function sharedTestSetup(options = {}) {
+function sharedTestSetup(options = {}) {
   this.sharedSetupCalled_ = true;
   // Sandbox created for greater control when certain stubs are cleared.
   this.sharedSetupSandbox_ = sinon.createSandbox();
@@ -125,13 +128,14 @@ export function sharedTestSetup(options = {}) {
   this.messagesCleanup_ = this.sharedCleanup.messagesCleanup_;
   wrapDefineBlocksWithJsonArrayWithCleanup_(this.sharedCleanup);
 }
+exports.sharedTestSetup = sharedTestSetup;
 
 /**
  * Shared cleanup method that clears up pending setTimeout calls, disposes of
  * workspace, and resets global variables. Should be called in setup of
  * outermost suite using sharedTestTeardown.call(this).
  */
-export function sharedTestTeardown() {
+function sharedTestTeardown() {
   const testRef = this.currentTest || this.test;
   if (!this.sharedSetupCalled_) {
     console.error('"' + testRef.fullTitle() + '" did not call sharedTestSetup');
@@ -179,6 +183,7 @@ export function sharedTestTeardown() {
     Blockly.WidgetDiv.testOnly_setDiv(null);
   }
 }
+exports.sharedTestTeardown = sharedTestTeardown;
 
 /**
  * Creates stub for Blockly.utils.genUid that returns the provided id or ids.
@@ -189,7 +194,7 @@ export function sharedTestTeardown() {
  *    that value.
  * @return {!SinonStub} The created stub.
  */
-export function createGenUidStubWithReturns(returnIds) {
+function createGenUidStubWithReturns(returnIds) {
   const stub = sinon.stub(Blockly.utils.idGenerator.TEST_ONLY, "genUid");
   if (Array.isArray(returnIds)) {
     for (let i = 0; i < returnIds.length; i++) {
@@ -200,3 +205,4 @@ export function createGenUidStubWithReturns(returnIds) {
   }
   return stub;
 }
+exports.createGenUidStubWithReturns = createGenUidStubWithReturns;
diff --git a/tests/mocha/test_helpers/toolbox_definitions.js b/tests/mocha/test_helpers/toolbox_definitions.js
index 0a7f2b9ef76..ee7ff576fce 100644
--- a/tests/mocha/test_helpers/toolbox_definitions.js
+++ b/tests/mocha/test_helpers/toolbox_definitions.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.toolboxDefinitions');
+goog.module('Blockly.test.helpers.toolboxDefinitions');
 
 
 /**
@@ -12,7 +12,7 @@ goog.declareModuleId('Blockly.test.helpers.toolboxDefinitions');
  * @return {Blockly.utils.toolbox.ToolboxJson} The array holding information
  *    for a toolbox.
  */
-export function getCategoryJSON() {
+function getCategoryJSON() {
   return {"contents": [
     {
       "kind": "CATEGORY",
@@ -42,13 +42,14 @@ export function getCategoryJSON() {
       "name": "Second",
     }]};
 }
+exports.getCategoryJSON = getCategoryJSON;
 
 /**
  * Get JSON for a simple toolbox.
  * @return {Blockly.utils.toolbox.ToolboxJson} The array holding information
  *    for a simple toolbox.
  */
-export function getSimpleJson() {
+function getSimpleJson() {
   return {"contents": [
     {
       "kind": "BLOCK",
@@ -82,8 +83,9 @@ export function getSimpleJson() {
     },
   ]};
 }
+exports.getSimpleJson = getSimpleJson;
 
-export function getProperSimpleJson() {
+function getProperSimpleJson() {
   return {
     "contents": [
       {
@@ -126,13 +128,14 @@ export function getProperSimpleJson() {
       },
     ]};
 }
+exports.getProperSimpleJson = getProperSimpleJson;
 
 /**
  * Get JSON for a toolbox that contains categories that contain categories.
  * @return {Blockly.utils.toolbox.ToolboxJson} The array holding information
  *    for a toolbox.
  */
-export function getDeeplyNestedJSON() {
+function getDeeplyNestedJSON() {
   return {"contents": [
     {
       "kind": "CATEGORY",
@@ -170,12 +173,13 @@ export function getDeeplyNestedJSON() {
       "name": "Second",
     }]};
 }
+exports.getDeeplyNestedJSON = getDeeplyNestedJSON;
 
 /**
  * Get an array filled with xml elements.
  * @return {Array<Node>} Array holding xml elements for a toolbox.
  */
-export function getXmlArray() {
+function getXmlArray() {
   const block = Blockly.Xml.textToDom(
       `<block type="logic_compare">
         <field name="OP">NEQ</field>
@@ -195,8 +199,9 @@ export function getXmlArray() {
   const label = Blockly.Xml.textToDom('<label text="tooltips"></label>');
   return [block, separator, button, label];
 }
+exports.getXmlArray = getXmlArray;
 
-export function getInjectedToolbox() {
+function getInjectedToolbox() {
   /**
    * Category: First
    *   sep
@@ -216,16 +221,18 @@ export function getInjectedToolbox() {
       });
   return workspace.getToolbox();
 }
+exports.getInjectedToolbox = getInjectedToolbox;
 
-export function getBasicToolbox() {
+function getBasicToolbox() {
   const workspace = new Blockly.WorkspaceSvg(new Blockly.Options({}));
   const toolbox = new Blockly.Toolbox(workspace);
   toolbox.HtmlDiv = document.createElement('div');
   toolbox.flyout_ = sinon.createStubInstance(Blockly.VerticalFlyout);
   return toolbox;
 }
+exports.getBasicToolbox = getBasicToolbox;
 
-export function getCollapsibleItem(toolbox) {
+function getCollapsibleItem(toolbox) {
   const contents = toolbox.contents_;
   for (let i = 0; i < contents.length; i++) {
     const item = contents[i];
@@ -234,8 +241,9 @@ export function getCollapsibleItem(toolbox) {
     }
   }
 }
+exports.getCollapsibleItem = getCollapsibleItem;
 
-export function getNonCollapsibleItem(toolbox) {
+function getNonCollapsibleItem(toolbox) {
   const contents = toolbox.contents_;
   for (let i = 0; i < contents.length; i++) {
     const item = contents[i];
@@ -244,11 +252,14 @@ export function getNonCollapsibleItem(toolbox) {
     }
   }
 }
+exports.getNonCollapsibleItem = getNonCollapsibleItem;
 
-export function getChildItem(toolbox) {
+function getChildItem(toolbox) {
   return toolbox.getToolboxItemById('nestedCategory');
 }
+exports.getChildItem = getChildItem;
 
-export function getSeparator(toolbox) {
+function getSeparator(toolbox) {
   return toolbox.getToolboxItemById('separator');
 }
+exports.getSeparator = getSeparator;
diff --git a/tests/mocha/test_helpers/user_input.js b/tests/mocha/test_helpers/user_input.js
index 2cae27bf11e..9482a7909d7 100644
--- a/tests/mocha/test_helpers/user_input.js
+++ b/tests/mocha/test_helpers/user_input.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.userInput');
+goog.module('Blockly.test.helpers.userInput');
 
 const {KeyCodes} = goog.require('Blockly.utils.KeyCodes');
 
@@ -17,7 +17,7 @@ const {KeyCodes} = goog.require('Blockly.utils.KeyCodes');
  * @param {Object<string, string>=} properties Properties to pass into event
  *    constructor.
  */
-export function dispatchPointerEvent(target, type, properties) {
+function dispatchPointerEvent(target, type, properties) {
   const eventInitDict = {
     cancelable: true,
     bubbles: true,
@@ -32,6 +32,7 @@ export function dispatchPointerEvent(target, type, properties) {
   const event = new PointerEvent(type, eventInitDict);
   target.dispatchEvent(event);
 }
+exports.dispatchPointerEvent = dispatchPointerEvent;
 
 /**
  * Creates a key down event used for testing.
@@ -39,7 +40,7 @@ export function dispatchPointerEvent(target, type, properties) {
  * @param {!Array<number>=} modifiers A list of modifiers. Use Blockly.utils.KeyCodes enum.
  * @return {!KeyboardEvent} The mocked keydown event.
  */
-export function createKeyDownEvent(keyCode, modifiers) {
+function createKeyDownEvent(keyCode, modifiers) {
   const event = {
     keyCode: keyCode,
   };
@@ -51,6 +52,7 @@ export function createKeyDownEvent(keyCode, modifiers) {
   }
   return new KeyboardEvent('keydown', event);
 }
+exports.createKeyDownEvent = createKeyDownEvent;
 
 /**
  * Simulates mouse click by triggering relevant mouse events.
@@ -58,8 +60,9 @@ export function createKeyDownEvent(keyCode, modifiers) {
  * @param {Object<string, string>=} properties Properties to pass into event
  *    constructor.
  */
-export function simulateClick(target, properties) {
+function simulateClick(target, properties) {
   dispatchPointerEvent(target, 'pointerdown', properties);
   dispatchPointerEvent(target, 'pointerup', properties);
   dispatchPointerEvent(target, 'click', properties);
 }
+exports.simulateClick = simulateClick;
diff --git a/tests/mocha/test_helpers/variables.js b/tests/mocha/test_helpers/variables.js
index e75047c06b9..f550e960bb4 100644
--- a/tests/mocha/test_helpers/variables.js
+++ b/tests/mocha/test_helpers/variables.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.variables');
+goog.module('Blockly.test.helpers.variables');
 
 
 /**
@@ -15,10 +15,11 @@ goog.declareModuleId('Blockly.test.helpers.variables');
  * @param {!string} type The expected type of the variable.
  * @param {!string} id The expected id of the variable.
  */
-export function assertVariableValues(container, name, type, id) {
+function assertVariableValues(container, name, type, id) {
   const variable = container.getVariableById(id);
   chai.assert.isDefined(variable);
   chai.assert.equal(variable.name, name);
   chai.assert.equal(variable.type, type);
   chai.assert.equal(variable.getId(), id);
 }
+exports.assertVariableValues = assertVariableValues;
diff --git a/tests/mocha/test_helpers/warnings.js b/tests/mocha/test_helpers/warnings.js
index 4d865857326..0457395cce7 100644
--- a/tests/mocha/test_helpers/warnings.js
+++ b/tests/mocha/test_helpers/warnings.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.warnings');
+goog.module('Blockly.test.helpers.warnings');
 
 
 /**
@@ -13,7 +13,7 @@ goog.declareModuleId('Blockly.test.helpers.warnings');
  * @param {Function} innerFunc The function where warnings may called.
  * @return {Array<string>} The warning messages (only the first arguments).
  */
-export function captureWarnings(innerFunc) {
+function captureWarnings(innerFunc) {
   const msgs = [];
   const nativeConsoleWarn = console.warn;
   try {
@@ -26,6 +26,7 @@ export function captureWarnings(innerFunc) {
   }
   return msgs;
 }
+exports.captureWarnings = captureWarnings;
 
 /**
  * Asserts that the given function logs the provided warning messages.
@@ -33,7 +34,7 @@ export function captureWarnings(innerFunc) {
  * @param {Array<!RegExp>|!RegExp} messages A list of regex for the expected
  *    messages (in the expected order).
  */
-export function assertWarnings(innerFunc, messages) {
+function assertWarnings(innerFunc, messages) {
   if (!Array.isArray(messages)) {
     messages = [messages];
   }
@@ -43,22 +44,25 @@ export function assertWarnings(innerFunc, messages) {
     chai.assert.match(warnings[i], message);
   });
 }
+exports.assertWarnings = assertWarnings;
 
 /**
  * Asserts that the given function logs no warning messages.
  * @param {function()} innerFunc The function to call.
  */
-export function assertNoWarnings(innerFunc) {
+function assertNoWarnings(innerFunc) {
   assertWarnings(innerFunc, []);
 }
+exports.assertNoWarnings = assertNoWarnings;
 
 /**
  * Stubs Blockly.utils.deprecation.warn call.
  * @return {!SinonStub} The created stub.
  */
-export function createDeprecationWarningStub() {
+function createDeprecationWarningStub() {
   return sinon.stub(Blockly.utils.deprecation, 'warn');
 }
+exports.createDeprecationWarningStub = createDeprecationWarningStub;
 
 /**
  * Asserts whether the given deprecation warning stub or call was called with
@@ -67,9 +71,10 @@ export function createDeprecationWarningStub() {
  * @param {string} functionName The function name to check that the given spy or
  *    spy call was called with.
  */
-export function assertDeprecationWarningCall(spyOrSpyCall, functionName) {
+function assertDeprecationWarningCall(spyOrSpyCall, functionName) {
   sinon.assert.calledWith(spyOrSpyCall, functionName);
 }
+exports.assertDeprecationWarningCall = assertDeprecationWarningCall;
 
 /**
  * Asserts that there was a single deprecation warning call with the given
@@ -78,7 +83,8 @@ export function assertDeprecationWarningCall(spyOrSpyCall, functionName) {
  * @param {string} functionName The function name to check that the given spy
  *    was called with.
  */
-export function assertSingleDeprecationWarningCall(spy, functionName) {
+function assertSingleDeprecationWarningCall(spy, functionName) {
   sinon.assert.calledOnce(spy);
   assertDeprecationWarningCall(spy.getCall(0), functionName);
 }
+exports.assertSingleDeprecationWarningCall = assertSingleDeprecationWarningCall;
diff --git a/tests/mocha/test_helpers/workspace.js b/tests/mocha/test_helpers/workspace.js
index ca1df255041..204a46df685 100644
--- a/tests/mocha/test_helpers/workspace.js
+++ b/tests/mocha/test_helpers/workspace.js
@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-goog.declareModuleId('Blockly.test.helpers.workspace');
+goog.module('Blockly.test.helpers.workspace');
 
 const {assertVariableValues} = goog.require('Blockly.test.helpers.variables');
 const {assertWarnings} = goog.require('Blockly.test.helpers.warnings');
@@ -12,7 +12,7 @@ const eventUtils = goog.require('Blockly.Events.utils');
 const {workspaceTeardown} = goog.require('Blockly.test.helpers.setupTeardown');
 
 
-export function testAWorkspace() {
+function testAWorkspace() {
   setup(function() {
     Blockly.defineBlocksWithJsonArray([{
       "type": "get_var_block",
@@ -1528,3 +1528,4 @@ export function testAWorkspace() {
     });
   });
 }
+exports.testAWorkspace = testAWorkspace;