diff --git a/src/core/friendly_errors/sketch_verifier.js b/src/core/friendly_errors/sketch_verifier.js
index fe88ab9fda..c646360f81 100644
--- a/src/core/friendly_errors/sketch_verifier.js
+++ b/src/core/friendly_errors/sketch_verifier.js
@@ -37,6 +37,16 @@ function sketchVerifier(p5, fn) {
     return userCode;
   }
 
+  /**
+   * Extracts the user-defined variables and functions from the user code with
+   * the help of Espree parser.
+   * 
+   * @method extractUserDefinedVariablesAndFuncs
+   * @param {string} codeStr - The code to extract variables and functions from.
+   * @returns {Object} An object containing the user's defined variables and functions.
+   * @returns {string[]} [userDefinitions.variables] Array of user-defined variable names.
+   * @returns {strings[]} [userDefinitions.functions] Array of user-defined function names.
+   */
   fn.extractUserDefinedVariablesAndFuncs = function (codeStr) {
     const userDefinitions = {
       variables: [],
@@ -53,23 +63,22 @@ function sketchVerifier(p5, fn) {
       });
 
       function traverse(node) {
-        switch (node.type) {
+        const { type, declarations, id, init } = node;
+
+        switch (type) {
           case 'VariableDeclaration':
-            node.declarations.forEach(declaration => {
-              if (declaration.id.type === 'Identifier') {
-                userDefinitions.variables.push(declaration.id.name);
+            declarations.forEach(({ id, init }) => {
+              if (id.type === 'Identifier') {
+                const category = init && ['ArrowFunctionExpression', 'FunctionExpression'].includes(init.type)
+                  ? 'functions'
+                  : 'variables';
+                userDefinitions[category].push(id.name);
               }
             });
             break;
           case 'FunctionDeclaration':
-            if (node.id && node.id.type === 'Identifier') {
-              userDefinitions.functions.push(node.id.name);
-            }
-            break;
-          case 'ArrowFunctionExpression':
-          case 'FunctionExpression':
-            if (node.parent && node.parent.type === 'VariableDeclarator') {
-              userDefinitions.functions.push(node.parent.id.name);
+            if (id?.type === 'Identifier') {
+              userDefinitions.functions.push(id.name);
             }
             break;
         }
@@ -87,6 +96,7 @@ function sketchVerifier(p5, fn) {
 
       traverse(ast);
     } catch (error) {
+      // TODO: Replace this with a friendly error message.
       console.error('Error parsing code:', error);
     }
 
@@ -96,7 +106,8 @@ function sketchVerifier(p5, fn) {
   fn.run = async function () {
     const userCode = await fn.getUserCode();
     const userDefinedVariablesAndFuncs = fn.extractUserDefinedVariablesAndFuncs(userCode);
-    console.log(userDefinedVariablesAndFuncs);
+
+    return userDefinedVariablesAndFuncs;
   }
 }
 
diff --git a/test/unit/core/sketch_overrides.js b/test/unit/core/sketch_overrides.js
new file mode 100644
index 0000000000..7c183ffd73
--- /dev/null
+++ b/test/unit/core/sketch_overrides.js
@@ -0,0 +1,142 @@
+import sketchVerifier from '../../../src/core/friendly_errors/sketch_verifier.js';
+
+suite('Validate Params', function () {
+  const mockP5 = {
+    _validateParameters: vi.fn()
+  };
+  const mockP5Prototype = {};
+
+  beforeAll(function () {
+    sketchVerifier(mockP5, mockP5Prototype);
+  });
+
+  afterAll(function () {
+  });
+
+  suite('fetchScript()', function () {
+    const url = 'https://www.p5test.com/sketch.js';
+    const code = 'p.createCanvas(200, 200);';
+
+    test('Fetches script content from src', async function () {
+      const mockFetch = vi.fn(() =>
+        Promise.resolve({
+          text: () => Promise.resolve(code)
+        })
+      );
+      vi.stubGlobal('fetch', mockFetch);
+
+      const mockScript = { src: url };
+      const result = await mockP5Prototype.fetchScript(mockScript);
+
+      expect(mockFetch).toHaveBeenCalledWith(url);
+      expect(result).toBe(code);
+
+      vi.unstubAllGlobals();
+    });
+
+    test('Fetches code when there is no src attribute', async function () {
+      const mockScript = { textContent: code };
+      const result = await mockP5Prototype.fetchScript(mockScript);
+
+      expect(result).toBe(code);
+    });
+  });
+
+  suite('getUserCode()', function () {
+    const userCode = "let c = p5.Color(20, 20, 20);";
+
+    test('fetches the last script element', async function () {
+      document.body.innerHTML = `
+        <script src="p5.js"></script>
+        <script src="www.p5test.com/sketch.js"></script>
+        <script>let c = p5.Color(20, 20, 20);</script>
+      `;
+
+      mockP5Prototype.fetchScript = vi.fn(() => Promise.resolve(userCode));
+
+      const result = await mockP5Prototype.getUserCode();
+
+      expect(mockP5Prototype.fetchScript).toHaveBeenCalledTimes(1);
+      expect(result).toBe(userCode);
+    });
+  });
+
+  suite('extractUserDefinedVariablesAndFuncs()', function () {
+    test('Extracts user-defined variables and functions', function () {
+      const code = `
+        let x = 5;
+        const y = 10;
+        var z = 15;
+        let v1, v2, v3
+        function foo() {}
+        const bar = () => {};
+        const baz = (x) => x * 2;
+      `;
+
+      const result = mockP5Prototype.extractUserDefinedVariablesAndFuncs(code);
+
+      expect(result.variables).toEqual(['x', 'y', 'z', 'v1', 'v2', 'v3']);
+      expect(result.functions).toEqual(['foo', 'bar', 'baz']);
+    });
+
+    // Sketch verifier should ignore the following types of lines:
+    //    - Comments (both single line and multi-line)
+    //    - Function calls
+    //    - Non-declaration code
+    test('Ignores other lines', function () {
+      const code = `
+        // This is a comment
+        let x = 5;
+        /* This is a multi-line comment.
+         * This is a multi-line comment.
+         */
+        const y = 10;
+        console.log("This is a statement");
+        foo(5);
+        p5.Math.random();
+        if (true) {
+          let z = 15;
+        }
+        for (let i = 0; i < 5; i++) {}
+      `;
+
+      const result = mockP5Prototype.extractUserDefinedVariablesAndFuncs(code);
+
+      expect(result.variables).toEqual(['x', 'y', 'z', 'i']);
+      expect(result.functions).toEqual([]);
+    });
+
+    test('Handles parsing errors', function () {
+      const invalidCode = 'let x = ;';
+      const consoleSpy = vi.spyOn(console, 'error').mockImplementation(() => { });
+
+      const result = mockP5Prototype.extractUserDefinedVariablesAndFuncs(invalidCode);
+
+      expect(consoleSpy).toHaveBeenCalled();
+      expect(result).toEqual({ variables: [], functions: [] });
+
+      consoleSpy.mockRestore();
+    });
+  });
+
+  suite('run()', function () {
+    test('Returns extracted variables and functions', async function () {
+      const mockScript = `
+        let x = 5;
+        const y = 10;
+        function foo() {}
+        const bar = () => {};
+      `;
+      mockP5Prototype.getUserCode = vi.fn(() => Promise.resolve(mockScript));
+
+      const result = await mockP5Prototype.run();
+
+      expect(mockP5Prototype.getUserCode).toHaveBeenCalledTimes(1);
+
+      expect(result).toEqual({
+        variables: ['x', 'y'],
+        functions: ['foo', 'bar']
+      });
+    });
+  });
+});
\ No newline at end of file
diff --git a/test/unit/spec.js b/test/unit/spec.js
index 995b152693..8df31317f2 100644
--- a/test/unit/spec.js
+++ b/test/unit/spec.js
@@ -13,6 +13,7 @@ var spec = {
     'param_errors',
     'preload',
     'rendering',
+    'sketch_overrides',
     'structure',
     'transform',
     'version',