diff --git a/components/theme-toggle.test.tsx b/components/theme-toggle.test.tsx
index 9f4f096..1995ab4 100644
--- a/components/theme-toggle.test.tsx
+++ b/components/theme-toggle.test.tsx
@@ -1,16 +1,43 @@
-import { describe, it, expect, vi } from "vitest";
+import { describe, it, expect, vi, beforeEach } from "vitest";
 import { render, screen, fireEvent } from "@testing-library/react";
 import { ThemeToggle } from "./theme-toggle";
 
-// Mock next-themes
-vi.mock("next-themes", () => ({
-  useTheme: () => ({
-    theme: "light",
-    setTheme: vi.fn(),
-  }),
-}));
+// Mock next-themes at the top level
+vi.mock("next-themes", () => {
+  const mockSetTheme = vi.fn();
+  return {
+    useTheme: vi.fn(() => ({
+      theme: "light",
+      setTheme: mockSetTheme,
+      resolvedTheme: "light",
+      systemTheme: "light",
+      themes: ["light", "dark"],
+      forcedTheme: undefined,
+    })),
+  };
+});
 
 describe("ThemeToggle", () => {
+  let mockSetTheme: ReturnType<typeof vi.fn>;
+
+  beforeEach(async () => {
+    vi.clearAllMocks();
+    // Get the mocked module
+    const nextThemes = await import("next-themes");
+    const useThemeMock = vi.mocked(nextThemes.useTheme);
+
+    // Create fresh mock for each test
+    mockSetTheme = vi.fn();
+    useThemeMock.mockReturnValue({
+      theme: "light",
+      setTheme: mockSetTheme,
+      resolvedTheme: "light",
+      systemTheme: "light",
+      themes: ["light", "dark"],
+      forcedTheme: undefined,
+    });
+  });
+
   it("should render the theme toggle button", () => {
     render(<ThemeToggle />);
     const button = screen.getByRole("button", { name: /toggle theme/i });
@@ -24,19 +51,32 @@ describe("ThemeToggle", () => {
     expect(sunIcon).toHaveClass("scale-100");
   });
 
-  it("should call setTheme when clicked", () => {
-    const mockSetTheme = vi.fn();
-    vi.mocked(vi.importActual("next-themes")).useTheme = () => ({
-      theme: "light",
+  it("should call setTheme when clicked", async () => {
+    render(<ThemeToggle />);
+    const button = screen.getByRole("button");
+    fireEvent.click(button);
+
+    expect(mockSetTheme).toHaveBeenCalledWith("dark");
+  });
+
+  it("should toggle to light theme when in dark mode", async () => {
+    // Update mock for dark mode
+    const nextThemes = await import("next-themes");
+    const useThemeMock = vi.mocked(nextThemes.useTheme);
+
+    useThemeMock.mockReturnValue({
+      theme: "dark",
       setTheme: mockSetTheme,
+      resolvedTheme: "dark",
+      systemTheme: "light",
+      themes: ["light", "dark"],
+      forcedTheme: undefined,
     });
 
     render(<ThemeToggle />);
     const button = screen.getByRole("button");
     fireEvent.click(button);
 
-    // Note: In a real test, we'd verify mockSetTheme was called
-    // but this is just an example to show the setup works
-    expect(button).toBeInTheDocument();
+    expect(mockSetTheme).toHaveBeenCalledWith("light");
   });
 });
diff --git a/lib/errors.test.ts b/lib/errors.test.ts
index 6fa61ba..48aee70 100644
--- a/lib/errors.test.ts
+++ b/lib/errors.test.ts
@@ -138,7 +138,8 @@ describe("handleError", () => {
   });
 
   it("should log errors with context", async () => {
-    const loggerModule = await vi.importMock("./logger");
+    const loggerModule =
+      await vi.importMock<typeof import("./logger")>("./logger");
     const error = new BadRequestError("Test error");
 
     handleError(error, "TestContext");
@@ -156,7 +157,7 @@ describe("handleError", () => {
 
 describe("withErrorHandling", () => {
   it("should wrap async handler and catch errors", async () => {
-    const handler = async () => {
+    const handler = async (): Promise<Response> => {
       throw new BadRequestError("Test error");
     };
 
diff --git a/lib/logger.test.ts b/lib/logger.test.ts
index 1f80211..8ce1634 100644
--- a/lib/logger.test.ts
+++ b/lib/logger.test.ts
@@ -64,13 +64,15 @@ describe("Logger", () => {
   describe("log levels in production", () => {
     beforeEach(async () => {
       // Change mock to return production
-      const env = await vi.importMock("./environment");
+      const env =
+        await vi.importMock<typeof import("./environment")>("./environment");
       vi.mocked(env.getCurrentEnvironment).mockReturnValue("production");
     });
 
     afterEach(async () => {
       // Reset to development
-      const env = await vi.importMock("./environment");
+      const env =
+        await vi.importMock<typeof import("./environment")>("./environment");
       vi.mocked(env.getCurrentEnvironment).mockReturnValue("development");
     });