diff --git a/__test__/hooks/answer.test.ts b/__test__/hooks/answer.test.ts
new file mode 100644
index 0000000..2b8a321
--- /dev/null
+++ b/__test__/hooks/answer.test.ts
@@ -0,0 +1,103 @@
+import { renderHook } from "@testing-library/react";
+import useSWR from "swr";
+import { Mock, vi } from "vitest";
+
+import useAnswers from "@/hooks/answer";
+import { testAnswer } from "@/types/Answer";
+import { AnswerResult, Result } from "@/types/_api";
+
+vi.mock("swr");
+
+beforeEach(() => {
+  // toHaveBeenCalledTimes がテストごとにリセットされるようにする
+  vi.clearAllMocks();
+});
+
+describe("useAnswer", () => {
+  it("回答一覧が取得できる", () => {
+    // setup
+    const mockResult: Result<AnswerResult> = {
+      code: 200,
+      data: {
+        answers: [testAnswer],
+      },
+    };
+
+    (useSWR as Mock).mockReturnValue({
+      data: mockResult,
+      mutate: vi.fn(),
+      isLoading: false,
+    });
+
+    // when
+    const { result } = renderHook(() => useAnswers("1"));
+
+    // then
+    expect(useSWR).toBeCalledWith("problems/1/answers", expect.any(Function));
+    expect(result.current.answers).toEqual(mockResult.data?.answers);
+    expect(result.current.getAnswer("1")).toEqual(testAnswer);
+    expect(result.current.mutate).toBeDefined();
+
+    // verify
+    expect(useSWR).toBeCalledTimes(1);
+  });
+
+  it("取得した回答一覧が空の時 answers, getAnswer が空になる", () => {
+    // setup
+    const mockResult: Result<AnswerResult> = {
+      code: 200,
+      data: null,
+    };
+
+    (useSWR as Mock).mockReturnValue({
+      data: mockResult,
+      mutate: vi.fn(),
+      isLoading: false,
+    });
+
+    // when
+    const { result } = renderHook(() => useAnswers("1"));
+
+    // then
+    expect(useSWR).toBeCalledWith("problems/1/answers", expect.any(Function));
+    expect(result.current.answers).toEqual([]);
+    expect(result.current.getAnswer("1")).toBeNull();
+    expect(result.current.mutate).toBeDefined();
+
+    // verify
+    expect(useSWR).toBeCalledTimes(1);
+  });
+
+  it("ProblemId で回答が見つからなかった時 getAnswer が空になる", () => {
+    // setup
+    const mockResult: Result<AnswerResult> = {
+      code: 200,
+      data: {
+        answers: [testAnswer],
+      },
+    };
+
+    (useSWR as Mock).mockReturnValue({
+      data: mockResult,
+      mutate: vi.fn(),
+      isLoading: false,
+    });
+
+    const id = "unknownId";
+
+    // when
+    const { result } = renderHook(() => useAnswers(id));
+
+    // then
+    expect(useSWR).toBeCalledWith(
+      `problems/${id}/answers`,
+      expect.any(Function)
+    );
+    expect(result.current.answers).toEqual(mockResult.data?.answers);
+    expect(result.current.getAnswer(id)).toBeNull();
+    expect(result.current.mutate).toBeDefined();
+
+    // verify
+    expect(useSWR).toBeCalledTimes(1);
+  });
+});
diff --git a/hooks/answer.ts b/hooks/answer.ts
index cd2e780..146b60d 100644
--- a/hooks/answer.ts
+++ b/hooks/answer.ts
@@ -2,10 +2,8 @@ import useSWR from "swr";
 
 import useApi from "@/hooks/api";
 import { Answer } from "@/types/Answer";
+import { AnswerResult } from "@/types/_api";
 
-type AnswerResult = {
-  answers: Answer[];
-};
 const useAnswers = (problemId: string | null) => {
   const { client } = useApi();
 
diff --git a/types/Answer.tsx b/types/Answer.tsx
index f6439ca..6754ab0 100644
--- a/types/Answer.tsx
+++ b/types/Answer.tsx
@@ -1,4 +1,4 @@
-import { UserGroup } from "@/types/UserGroup";
+import { testUserGroup, UserGroup } from "@/types/UserGroup";
 
 export type Answer = {
   id: string;
@@ -9,3 +9,13 @@ export type Answer = {
   created_at: string;
   updated_at: string;
 };
+
+export const testAnswer: Answer = {
+  id: "1",
+  body: "test",
+  point: 100,
+  problem_id: "1",
+  user_group: testUserGroup,
+  created_at: "2021-01-01",
+  updated_at: "2021-01-01",
+};
diff --git a/types/User.ts b/types/User.ts
index 9380cd3..c25425d 100644
--- a/types/User.ts
+++ b/types/User.ts
@@ -1,4 +1,4 @@
-import { UserGroup } from "@/types/UserGroup";
+import { testUserGroup, UserGroup } from "@/types/UserGroup";
 
 export type User = {
   id: string;
@@ -69,16 +69,7 @@ export const testAdminUser: User = {
   is_read_only: false,
   created_at: new Date(),
   updated_at: new Date(),
-  user_group: {
-    id: "1",
-    name: "Test User Group",
-    organization: "Test Organization",
-    created_at: new Date(),
-    updated_at: new Date(),
-    is_full_access: true,
-    members: [],
-    bastion: null,
-  },
+  user_group: testUserGroup,
   user_group_id: "1",
   profile: {
     id: "1",
diff --git a/types/UserGroup.ts b/types/UserGroup.ts
index c952026..e0bb0e7 100644
--- a/types/UserGroup.ts
+++ b/types/UserGroup.ts
@@ -15,3 +15,14 @@ export type UserGroup = {
     bastion_port: number;
   } | null;
 };
+
+export const testUserGroup: UserGroup = {
+  id: "1",
+  name: "Test User Group",
+  organization: "Test Organization",
+  created_at: new Date(),
+  updated_at: new Date(),
+  is_full_access: true,
+  members: [],
+  bastion: null,
+};
diff --git a/types/_api.ts b/types/_api.ts
index 62099f5..b4c48e7 100644
--- a/types/_api.ts
+++ b/types/_api.ts
@@ -19,5 +19,5 @@ export type ProblemResult = {
 
 // /api/problems/:id/answers
 export type AnswerResult = {
-  answer: Answer;
+  answers: Answer[];
 };