diff --git a/pr_description.md b/pr_description.md
index 3cb0334..207452a 100644
--- a/pr_description.md
+++ b/pr_description.md
@@ -1,10 +1,11 @@
-🔒 HTTPヘッダーインジェクションの脆弱性修正
+🧪 [testing improvement] Add comprehensive unit tests for SearchForm component
 
-🎯 **What:**
-`src/lib/githubViewer.ts` と `src/lib/github.ts` において、セッショントークンを検証せずに直接 `fetch` 呼び出しの `Authorization` ヘッダーに渡していた脆弱性を修正しました。
-
-⚠️ **Risk:**
-不適切なトークン検証により、攻撃者がトークン内に `\r\n`（CRLF）などの改行文字を含めることで、HTTPヘッダーインジェクションやSSRF（Server-Side Request Forgery）攻撃を引き起こす可能性がありました。これにより、任意のAPIリクエストが実行されたり、セッションハイジャックのリスクが生じる恐れがありました。
-
-🛡️ **Solution:**
-APIを呼び出す前に、提供されたトークンが標準のGitHubトークン形式（英数字、ハイフン、アンダースコア、等号のみ）に一致するかを検証する正規表現チェック（`/^[A-Za-z0-9_=-]+$/`）を追加しました。無効なフォーマットの場合は、APIリクエストを行う前に `GitHubApiError` がスローされます。
+🎯 **What:** The `SearchForm` component lacked unit tests, leaving critical user interaction (searching for GitHub users) unverified.
+📊 **Coverage:** This PR adds `src/components/SearchForm.test.tsx` utilizing `@testing-library/react` and `vitest`. The test suite now covers:
+  - Form rendering (input and submit button).
+  - State updates when typing in the input.
+  - Form submission logic and conditional disabling of the search button for empty inputs.
+  - Ensuring whitespace-only submissions are prevented.
+  - Verification that the username is trimmed and URI encoded properly before calling `router.push`.
+  - Simulating the React `useTransition` loading state where the button becomes disabled and displays "Loading...".
+✨ **Result:** Enhanced test coverage and reliability for user search workflows. Improved testing confidence by mocking `next/navigation` and React hooks effectively.
diff --git a/src/components/SearchForm.test.tsx b/src/components/SearchForm.test.tsx
new file mode 100644
index 0000000..4584986
--- /dev/null
+++ b/src/components/SearchForm.test.tsx
@@ -0,0 +1,118 @@
+/**
+ * @vitest-environment jsdom
+ */
+import { render, screen, fireEvent, waitFor } from "@testing-library/react";
+import { describe, it, expect, vi, beforeEach } from "vitest";
+import SearchForm from "./SearchForm";
+import * as React from "react";
+
+// Mock next/navigation
+const pushMock = vi.fn();
+vi.mock("next/navigation", () => ({
+  useRouter: () => ({
+    push: pushMock,
+  }),
+}));
+
+// Provide a mock implementation that we can spy on later
+const useTransitionMock = vi.fn<() => [boolean, (cb: () => void) => void]>();
+
+vi.mock("react", async (importOriginal) => {
+  const actual = await importOriginal<typeof import("react")>();
+  return {
+    ...actual,
+    useTransition: () => useTransitionMock(),
+  };
+});
+
+describe("SearchForm", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    useTransitionMock.mockReturnValue([false, (cb: () => void) => cb()]);
+  });
+
+  it("renders the input and search button", () => {
+    render(<SearchForm />);
+    expect(screen.getByPlaceholderText("GitHub username")).toBeDefined();
+    expect(screen.getByRole("button", { name: "Search" })).toBeDefined();
+  });
+
+  it("updates input value when typing", () => {
+    render(<SearchForm />);
+    const input = screen.getByPlaceholderText("GitHub username") as HTMLInputElement;
+    fireEvent.change(input, { target: { value: "johndoe" } });
+    expect(input.value).toBe("johndoe");
+  });
+
+  it("disables the search button when input is empty", () => {
+    render(<SearchForm />);
+    const button = screen.getByRole("button", { name: "Search" }) as HTMLButtonElement;
+    expect(button.disabled).toBe(true);
+  });
+
+  it("enables the search button only when input has non-whitespace text", () => {
+    render(<SearchForm />);
+    const input = screen.getByPlaceholderText("GitHub username");
+    const button = screen.getByRole("button", { name: "Search" }) as HTMLButtonElement;
+
+    fireEvent.change(input, { target: { value: "   " } });
+    expect(button.disabled).toBe(true);
+
+    fireEvent.change(input, { target: { value: "johndoe" } });
+    expect(button.disabled).toBe(false);
+  });
+
+  it("calls router.push with the username on form submission", async () => {
+    render(<SearchForm />);
+    const input = screen.getByPlaceholderText("GitHub username");
+    const button = screen.getByRole("button", { name: "Search" });
+
+    fireEvent.change(input, { target: { value: "johndoe" } });
+    fireEvent.click(button);
+
+    await waitFor(() => {
+      expect(pushMock).toHaveBeenCalledWith("/johndoe");
+    });
+  });
+
+  it("trims the username and URI encodes it before submission", async () => {
+    render(<SearchForm />);
+    const input = screen.getByPlaceholderText("GitHub username");
+    const button = screen.getByRole("button", { name: "Search" });
+
+    // Using a username with spaces and special characters
+    fireEvent.change(input, { target: { value: "  john doe/test  " } });
+    fireEvent.click(button);
+
+    await waitFor(() => {
+      // "john doe/test" encoded is "john%20doe%2Ftest"
+      expect(pushMock).toHaveBeenCalledWith("/john%20doe%2Ftest");
+    });
+  });
+
+  it("does not call router.push if input is only whitespace", () => {
+    render(<SearchForm />);
+    const input = screen.getByPlaceholderText("GitHub username");
+
+    fireEvent.change(input, { target: { value: "   " } });
+
+    // The button should be disabled, but we can also trigger submit on the form directly
+    // to ensure the internal check `if (trimmed)` works
+    const form = input.closest("form")!;
+    fireEvent.submit(form);
+
+    expect(pushMock).not.toHaveBeenCalled();
+  });
+
+  it("disables button and shows 'Loading...' when isPending is true", () => {
+    // Mock useTransition to return [true, startTransition]
+    useTransitionMock.mockReturnValue([
+      true, // isPending
+      vi.fn() as unknown as React.TransitionStartFunction, // startTransition
+    ]);
+
+    render(<SearchForm />);
+    const button = screen.getByRole("button", { name: "Loading..." }) as HTMLButtonElement;
+    expect(button.disabled).toBe(true);
+  });
+});