diff --git a/libs/core/.eslintignore b/libs/core/.eslintignore
index 17f207a89..7f6bfd2b3 100644
--- a/libs/core/.eslintignore
+++ b/libs/core/.eslintignore
@@ -4,3 +4,4 @@
 **/*.stories.*
 **/*.figma.ts
 stencil.config.ts
+src/utils/test/setup.ts
diff --git a/libs/core/src/utils/test/setup.ts b/libs/core/src/utils/test/setup.ts
new file mode 100644
index 000000000..9b3efe27c
--- /dev/null
+++ b/libs/core/src/utils/test/setup.ts
@@ -0,0 +1,157 @@
+/**
+ * Global test setup file
+ * This file is loaded before all tests to provide mocks and polyfills
+ */
+
+/**
+ * Mock ElementInternals API for testing
+ * The ElementInternals API is used for form-associated custom elements
+ * but is not fully supported in Stencil's unit test environment
+ */
+class MockElementInternals {
+  // @ts-expect-error - Stored for mock completeness
+  private _formValue: FormData | string | null = null;
+  // @ts-expect-error - Stored for mock completeness
+  private _formState: FormData | string | null = null;
+  private _validationMessage = '';
+  private _validity: ValidityState = {
+    badInput: false,
+    customError: false,
+    patternMismatch: false,
+    rangeOverflow: false,
+    rangeUnderflow: false,
+    stepMismatch: false,
+    tooLong: false,
+    tooShort: false,
+    typeMismatch: false,
+    valid: true,
+    valueMissing: false,
+  };
+
+  /**
+   * Sets the form value and state for the associated custom element
+   */
+  setFormValue(
+    value: File | string | FormData | null,
+    state?: File | string | FormData | null,
+  ): void {
+    this._formValue = value as FormData | string | null;
+    this._formState = state !== undefined ? (state as FormData | string | null) : value as FormData | string | null;
+  }
+
+  /**
+   * Sets the validity state and validation message
+   */
+  setValidity(
+    flags?: ValidityStateFlags,
+    message?: string,
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    _anchor?: HTMLElement,
+  ): void {
+    if (flags) {
+      this._validity = { ...this._validity, ...flags, valid: !Object.values(flags).some(Boolean) };
+    }
+    this._validationMessage = message || '';
+  }
+
+  /**
+   * Checks if the element will pass validation
+   */
+  checkValidity(): boolean {
+    return this._validity.valid;
+  }
+
+  /**
+   * Checks validity and fires invalid event if not valid
+   */
+  reportValidity(): boolean {
+    return this._validity.valid;
+  }
+
+  /**
+   * Returns the form associated with this element
+   */
+  get form(): HTMLFormElement | null {
+    return null;
+  }
+
+  /**
+   * Returns the validation message
+   */
+  get validationMessage(): string {
+    return this._validationMessage;
+  }
+
+  /**
+   * Returns the validity state
+   */
+  get validity(): ValidityState {
+    return this._validity;
+  }
+
+  /**
+   * Returns whether the element will be validated
+   */
+  get willValidate(): boolean {
+    return true;
+  }
+
+  /**
+   * Returns the labels associated with this element
+   */
+  get labels(): NodeList {
+    return {
+      length: 0,
+      item: () => null,
+      // eslint-disable-next-line @typescript-eslint/no-empty-function
+      [Symbol.iterator]: function* () {},
+    } as unknown as NodeList;
+  }
+}
+
+/**
+ * Mock attachInternals method on HTMLElement
+ */
+if (typeof HTMLElement !== 'undefined' && typeof HTMLElement.prototype.attachInternals === 'undefined') {
+  HTMLElement.prototype.attachInternals = function () {
+    return new MockElementInternals() as unknown as ElementInternals;
+  };
+}
+
+/**
+ * Suppress specific console warnings that are expected in test environment
+ */
+const originalConsoleError = console.error;
+const originalConsoleWarn = console.warn;
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+console.error = (...args: any[]) => {
+  const message = typeof args[0] === 'string' ? args[0] : '';
+
+  // Filter out the ElementInternals warning since we're mocking it
+  if (message.includes('Property setFormValue was accessed on ElementInternals')) {
+    return;
+  }
+
+  // Filter out SVG icon 404 errors in e2e tests (icons aren't available on test server)
+  if (message.includes('Failed to load resource') && message.includes('pds-icons/svg')) {
+    return;
+  }
+
+  originalConsoleError.apply(console, args);
+};
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+console.warn = (...args: any[]) => {
+  const message = typeof args[0] === 'string' ? args[0] : '';
+
+  // Filter out SVG icon loading warnings in e2e tests (icons aren't available on test server)
+  if (message.includes('Failed to load SVG') && message.includes('pds-icons/svg')) {
+    return;
+  }
+
+  originalConsoleWarn.apply(console, args);
+};
+
+export {};
+
diff --git a/libs/core/stencil.config.ts b/libs/core/stencil.config.ts
index e4c7e21e3..adde4dbf0 100644
--- a/libs/core/stencil.config.ts
+++ b/libs/core/stencil.config.ts
@@ -11,6 +11,15 @@ export const config: Config = {
     openBrowser: false,
     port: 7300,
   },
+  testing: {
+    setupFilesAfterEnv: ['<rootDir>/src/utils/test/setup.ts'],
+    coveragePathIgnorePatterns: [
+      '/node_modules/',
+      '/dist/',
+      '/www/',
+      'setup.ts'
+    ],
+  },
   outputTargets: [
     {
       type: 'dist',
diff --git a/libs/core/tsconfig.json b/libs/core/tsconfig.json
index 67a50d611..fd861679b 100644
--- a/libs/core/tsconfig.json
+++ b/libs/core/tsconfig.json
@@ -30,6 +30,7 @@
     "**/*.stories.ts",
     "**/*.stories.tsx",
     "**/*.figma.ts",
-    "scripts/custom-elements"
+    "scripts/custom-elements",
+    "src/utils/test/setup.ts"
   ]
 }