diff --git a/tests/javascripts/notifyModal.test.js b/tests/javascripts/notifyModal.test.js
new file mode 100644
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--- /dev/null
+++ b/tests/javascripts/notifyModal.test.js
@@ -0,0 +1,120 @@
+/**
+ * @jest-environment jsdom
+ */
+
+const { openModal, closeModal } = require("../../app/assets/javascripts/modal"); // adjust path if needed
+
+describe("Modal functionality", () => {
+  let modalWrapper, modalElement, openBtn, closeBtn, anotherFocusable;
+
+  beforeEach(() => {
+    document.body.innerHTML = `
+      <button data-open-modal="myModal">Open Modal</button>
+
+      <div id="myModal" class="is-hidden">
+        <div class="usa-modal">
+          <div class="usa-modal-overlay">
+            <div class="usa-modal-content">
+              <button data-close-modal>Close</button>
+              <a href="#">Focusable Link</a>
+              <input type="text" />
+            </div>
+          </div>
+        </div>
+      </div>
+    `;
+
+    modalWrapper = document.getElementById("myModal");
+    modalElement = modalWrapper.querySelector(".usa-modal");
+    openBtn = document.querySelector('[data-open-modal]');
+    closeBtn = modalWrapper.querySelector('[data-close-modal]');
+    anotherFocusable = modalWrapper.querySelector('a');
+  });
+
+  afterEach(() => {
+    document.body.innerHTML = "";
+  });
+
+  test("Opens the modal and sets focus to the first focusable element", () => {
+    document.activeElement.blur(); // ensure focus starts elsewhere
+    openModal("myModal");
+
+    expect(modalWrapper.classList.contains("is-hidden")).toBe(false);
+    expect(modalElement.hasAttribute("aria-hidden")).toBe(false);
+    expect(modalElement.hasAttribute("inert")).toBe(false);
+    expect(modalElement.hasAttribute("hidden")).toBe(false);
+    expect(document.body.classList.contains("modal-open")).toBe(true);
+    expect(document.activeElement).toBe(closeBtn);
+  });
+
+  test("Closes the modal and restores focus", () => {
+    openBtn.focus();
+    openModal("myModal");
+    closeModal();
+
+    expect(modalWrapper.classList.contains("is-hidden")).toBe(true);
+    expect(modalElement.getAttribute("aria-hidden")).toBe("true");
+    expect(modalElement.hasAttribute("inert")).toBe(true);
+    expect(modalElement.hasAttribute("hidden")).toBe(true);
+    expect(document.body.classList.contains("modal-open")).toBe(false);
+    expect(document.activeElement).toBe(openBtn);
+  });
+
+  test("Closes the modal when pressing Escape", () => {
+    openModal("myModal");
+
+    const event = new KeyboardEvent("keydown", { key: "Escape" });
+    document.dispatchEvent(event);
+
+    expect(modalWrapper.classList.contains("is-hidden")).toBe(true);
+  });
+
+  test("Traps focus within the modal when Tab is pressed", () => {
+    openModal("myModal");
+
+    const focusableElements = modalElement.querySelectorAll(
+      'a[href], area[href], input:not([disabled]), select:not([disabled]), textarea:not([disabled]), button:not([disabled]), [tabindex]:not([tabindex="-1"])'
+    );
+
+    focusableElements[focusableElements.length - 1].focus(); // Last element
+
+    const tabEvent = new KeyboardEvent("keydown", {
+      key: "Tab",
+      bubbles: true
+    });
+
+    modalElement.dispatchEvent(tabEvent);
+    expect(document.activeElement).toBe(focusableElements[0]);
+  });
+
+  test("Traps focus backwards when Shift+Tab is pressed from first element", () => {
+    openModal("myModal");
+
+    const focusableElements = modalElement.querySelectorAll(
+      'a[href], area[href], input:not([disabled]), select:not([disabled]), textarea:not([disabled]), button:not([disabled]), [tabindex]:not([tabindex="-1"])'
+    );
+
+    focusableElements[0].focus(); // First element
+
+    const shiftTabEvent = new KeyboardEvent("keydown", {
+      key: "Tab",
+      shiftKey: true,
+      bubbles: true
+    });
+
+    modalElement.dispatchEvent(shiftTabEvent);
+    expect(document.activeElement).toBe(focusableElements[focusableElements.length - 1]);
+  });
+
+  test("Closes modal when clicking on overlay", () => {
+    openModal("myModal");
+    const overlay = modalElement.querySelector(".usa-modal-overlay");
+
+    const clickEvent = new MouseEvent("click", {
+      bubbles: true
+    });
+
+    overlay.dispatchEvent(clickEvent);
+    expect(modalWrapper.classList.contains("is-hidden")).toBe(true);
+  });
+});