diff --git a/tests/Theme.test.svelte b/tests/Theme.test.svelte
deleted file mode 100644
index 929e5386..00000000
--- a/tests/Theme.test.svelte
+++ /dev/null
@@ -1,24 +0,0 @@
-<script lang="ts">
-  import { Theme } from "carbon-components-svelte";
-  import type { CarbonTheme } from "carbon-components-svelte/Theme/Theme.svelte";
-
-  let theme: CarbonTheme = "g10";
-</script>
-
-<Theme
-  bind:theme
-  persist
-  persistKey="carbon-theme"
-  on:update={(e) => console.log(e.detail.theme)}
-  tokens={{ "button-primary": "violet" }}
-  render="toggle"
-  toggle={{
-    themes: ["g10", "g90"],
-    labelA: "",
-    labelB: "",
-  }}
-  select={{
-    themes: ["g10", "g90"],
-    labelText: "",
-  }}
-/>
diff --git a/tests/Theme/Theme.test.svelte b/tests/Theme/Theme.test.svelte
new file mode 100644
index 00000000..1fadc6b3
--- /dev/null
+++ b/tests/Theme/Theme.test.svelte
@@ -0,0 +1,23 @@
+<svelte:options accessors />
+
+<script lang="ts">
+  import { Theme } from "carbon-components-svelte";
+  import type { CarbonTheme } from "carbon-components-svelte/Theme/Theme.svelte";
+
+  export let theme: CarbonTheme = "white";
+  export let persist = false;
+  export let tokens = {};
+</script>
+
+<div data-testid="theme-wrapper">
+  <Theme
+    {theme}
+    {persist}
+    {tokens}
+    on:update={({ detail }) => {
+      console.log("update", detail);
+    }}
+  >
+    <slot />
+  </Theme>
+</div>
diff --git a/tests/Theme/Theme.test.ts b/tests/Theme/Theme.test.ts
new file mode 100644
index 00000000..9758855a
--- /dev/null
+++ b/tests/Theme/Theme.test.ts
@@ -0,0 +1,168 @@
+import { render, screen } from "@testing-library/svelte";
+import { tick } from "svelte";
+import { user } from "../setup-tests";
+import Theme from "./Theme.test.svelte";
+import ThemeSelect from "./ThemeSelect.test.svelte";
+import ThemeSelectCustom from "./ThemeSelectCustom.test.svelte";
+import ThemeToggle from "./ThemeToggle.test.svelte";
+import ThemeToggleCustom from "./ThemeToggleCustom.test.svelte";
+
+describe("Theme", () => {
+  let documentMock: {
+    setAttribute: ReturnType<typeof vi.spyOn>;
+    style: { setProperty: ReturnType<typeof vi.spyOn> };
+  };
+  let consoleLog: ReturnType<typeof vi.spyOn>;
+  let localStorageMock: Record<string, string>;
+  let originalLocalStorage: Storage;
+
+  beforeEach(() => {
+    documentMock = {
+      setAttribute: vi.spyOn(document.documentElement, "setAttribute"),
+      style: {
+        setProperty: vi.spyOn(document.documentElement.style, "setProperty"),
+      },
+    };
+    consoleLog = vi.spyOn(console, "log");
+    originalLocalStorage = global.localStorage;
+    localStorageMock = {};
+
+    global.localStorage = {
+      getItem: vi.fn((key) => localStorageMock[key] || null),
+      setItem: vi.fn((key, value) => {
+        localStorageMock[key] = value;
+      }),
+      removeItem: vi.fn((key) => {
+        delete localStorageMock[key];
+      }),
+      clear: vi.fn(() => {
+        localStorageMock = {};
+      }),
+      length: 0,
+      key: vi.fn(),
+    };
+  });
+
+  afterEach(() => {
+    vi.restoreAllMocks();
+    global.localStorage = originalLocalStorage;
+    localStorage.clear();
+    localStorageMock = {};
+  });
+
+  it("should set default theme to white", () => {
+    render(Theme);
+    expect(documentMock.setAttribute).toHaveBeenCalledWith("theme", "white");
+  });
+
+  it("should update theme attribute when theme changes", async () => {
+    const { component } = render(Theme);
+
+    component.$set({ theme: "g100" });
+    await tick();
+
+    expect(documentMock.setAttribute).toHaveBeenCalledWith("theme", "g100");
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "g100" });
+  });
+
+  it("should apply custom tokens", async () => {
+    const tokens = {
+      "interactive-01": "#ff0000",
+      "ui-background": "#ffffff",
+    };
+
+    render(Theme, { props: { tokens } });
+    await tick();
+
+    expect(documentMock.style.setProperty).toHaveBeenCalledWith(
+      "--cds-interactive-01",
+      "#ff0000",
+    );
+    expect(documentMock.style.setProperty).toHaveBeenCalledWith(
+      "--cds-ui-background",
+      "#ffffff",
+    );
+  });
+
+  it("should persist theme in localStorage when persist is true", async () => {
+    render(Theme, { props: { persist: true } });
+    await tick();
+
+    expect(localStorage.setItem).toHaveBeenCalledWith("theme", "white");
+  });
+
+  it("should load persisted theme from localStorage", async () => {
+    localStorageMock["theme"] = "g90";
+
+    render(Theme, { props: { persist: true } });
+    await tick();
+
+    expect(documentMock.setAttribute).toHaveBeenCalledWith("theme", "g90");
+  });
+
+  it("should warn on invalid theme", async () => {
+    const consoleWarn = vi.spyOn(console, "warn");
+    const { component } = render(Theme);
+
+    // @ts-ignore - Testing invalid theme
+    component.$set({ theme: "invalid" });
+    await tick();
+
+    expect(consoleWarn).toHaveBeenCalledWith(
+      expect.stringContaining('invalid theme "invalid"'),
+    );
+  });
+
+  it("should render toggle when render prop is set to toggle", async () => {
+    render(ThemeToggle);
+
+    const toggle = screen.getByLabelText("Dark mode");
+    expect(toggle).toBeInTheDocument();
+    expect(toggle).toHaveAttribute("type", "checkbox");
+
+    await user.click(toggle);
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "g100" });
+
+    await user.click(toggle);
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "white" });
+  });
+
+  it("should render custom toggle when render prop is set to toggle and custom toggle options are provided", async () => {
+    render(ThemeToggleCustom);
+
+    const toggle = screen.getAllByText("Enable dark mode")[0];
+    expect(toggle).toBeInTheDocument();
+
+    await user.click(toggle);
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "g80" });
+
+    await user.click(toggle);
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "g10" });
+  });
+
+  it("should render select when render prop is set to select", async () => {
+    render(ThemeSelect);
+
+    const select = screen.getByLabelText("Themes");
+    expect(select).toBeInTheDocument();
+
+    await user.selectOptions(select, "g100");
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "g100" });
+
+    await user.selectOptions(select, "white");
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "white" });
+  });
+
+  it("should render custom select when render prop is set to select and custom select options are provided", async () => {
+    render(ThemeSelectCustom);
+
+    const select = screen.getByLabelText("Select a theme");
+    expect(select).toBeInTheDocument();
+
+    await user.selectOptions(select, "g100");
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "g100" });
+
+    await user.selectOptions(select, "white");
+    expect(consoleLog).toHaveBeenCalledWith("update", { theme: "white" });
+  });
+});
diff --git a/tests/Theme/ThemeSelect.test.svelte b/tests/Theme/ThemeSelect.test.svelte
new file mode 100644
index 00000000..3648b3ef
--- /dev/null
+++ b/tests/Theme/ThemeSelect.test.svelte
@@ -0,0 +1,10 @@
+<script lang="ts">
+  import { Theme } from "carbon-components-svelte";
+</script>
+
+<Theme
+  render="select"
+  on:update={({ detail }) => {
+    console.log("update", detail);
+  }}
+/>
diff --git a/tests/Theme/ThemeSelectCustom.test.svelte b/tests/Theme/ThemeSelectCustom.test.svelte
new file mode 100644
index 00000000..93fbfea3
--- /dev/null
+++ b/tests/Theme/ThemeSelectCustom.test.svelte
@@ -0,0 +1,15 @@
+<script lang="ts">
+  import { Theme } from "carbon-components-svelte";
+</script>
+
+<Theme
+  render="select"
+  select={{
+    themes: ["white", "g90", "g100"],
+    labelText: "Select a theme",
+    inline: true,
+  }}
+  on:update={({ detail }) => {
+    console.log("update", detail);
+  }}
+/>
diff --git a/tests/Theme/ThemeToggle.test.svelte b/tests/Theme/ThemeToggle.test.svelte
new file mode 100644
index 00000000..6512a23d
--- /dev/null
+++ b/tests/Theme/ThemeToggle.test.svelte
@@ -0,0 +1,10 @@
+<script lang="ts">
+  import { Theme } from "carbon-components-svelte";
+</script>
+
+<Theme
+  render="toggle"
+  on:update={({ detail }) => {
+    console.log("update", detail);
+  }}
+/>
diff --git a/tests/Theme/ThemeToggleCustom.test.svelte b/tests/Theme/ThemeToggleCustom.test.svelte
new file mode 100644
index 00000000..c3f8a01e
--- /dev/null
+++ b/tests/Theme/ThemeToggleCustom.test.svelte
@@ -0,0 +1,17 @@
+<script lang="ts">
+  import { Theme } from "carbon-components-svelte";
+</script>
+
+<Theme
+  render="toggle"
+  toggle={{
+    themes: ["g10", "g80"],
+    labelA: "Enable dark mode",
+    labelB: "Enable dark mode",
+    hideLabel: true,
+    size: "sm",
+  }}
+  on:update={({ detail }) => {
+    console.log("update", detail);
+  }}
+/>