diff --git a/go.mod b/go.mod
index cb09af0..2189653 100644
--- a/go.mod
+++ b/go.mod
@@ -9,6 +9,7 @@ require (
 	github.com/joho/godotenv v1.5.1
 	github.com/oapi-codegen/gin-middleware v1.0.2
 	github.com/oapi-codegen/runtime v1.1.2
+	github.com/stretchr/testify v1.11.1
 	google.golang.org/api v0.231.0
 )
 
@@ -34,6 +35,7 @@ require (
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/cloudwego/base64x v0.1.6 // indirect
 	github.com/cncf/xds/go v0.0.0-20250501225837-2ac532fd4443 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/dprotaso/go-yit v0.0.0-20220510233725-9ba8df137936 // indirect
 	github.com/envoyproxy/go-control-plane/envoy v1.32.4 // indirect
 	github.com/envoyproxy/protoc-gen-validate v1.2.1 // indirect
@@ -72,6 +74,7 @@ require (
 	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
 	github.com/perimeterx/marshmallow v1.1.5 // indirect
 	github.com/planetscale/vtprotobuf v0.6.1-0.20240319094008-0393e58bdf10 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/quic-go/qpack v0.5.1 // indirect
 	github.com/quic-go/quic-go v0.55.0 // indirect
 	github.com/rogpeppe/go-internal v1.14.1 // indirect
diff --git a/internal/handler/announcement.go b/internal/handler/announcement.go
index 1841ed4..e867cc0 100644
--- a/internal/handler/announcement.go
+++ b/internal/handler/announcement.go
@@ -78,6 +78,7 @@ func (h *Handler) AnnouncementsV1Delete(c *gin.Context, id string) {
 	}
 
 	c.Status(http.StatusNoContent)
+	c.Writer.WriteHeaderNow()
 }
 
 // AnnouncementsV1Update 更新する
diff --git a/internal/handler/announcement_test.go b/internal/handler/announcement_test.go
new file mode 100644
index 0000000..4ceefba
--- /dev/null
+++ b/internal/handler/announcement_test.go
@@ -0,0 +1,557 @@
+package handler_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"firebase.google.com/go/v4/auth"
+	api "github.com/fun-dotto/api-template/generated"
+	"github.com/fun-dotto/api-template/internal/handler"
+	"github.com/fun-dotto/api-template/internal/middleware"
+	"github.com/fun-dotto/api-template/internal/repository"
+	"github.com/fun-dotto/api-template/internal/service"
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// setupTestContext Firebase認証をモックしたテストコンテキストを作成する
+func setupTestContext(withAdminClaim bool) (*httptest.ResponseRecorder, *gin.Context) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+
+	// Requestを初期化
+	c.Request = httptest.NewRequest(http.MethodGet, "/", nil)
+
+	if withAdminClaim {
+		// Firebaseトークンをモック
+		token := &auth.Token{
+			Claims: map[string]interface{}{
+				"admin": true,
+			},
+		}
+		c.Set(middleware.FirebaseTokenContextKey, token)
+	}
+
+	return w, c
+}
+
+// setupTestContextWithClaims 指定したクレームでFirebaseトークンをモックしたテストコンテキストを作成する（403など権限不足の検証用）
+func setupTestContextWithClaims(claims map[string]interface{}) (*httptest.ResponseRecorder, *gin.Context) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodGet, "/", nil)
+	token := &auth.Token{Claims: claims}
+	c.Set(middleware.FirebaseTokenContextKey, token)
+	return w, c
+}
+
+func TestAnnouncementsV1List(t *testing.T) {
+	tests := []struct {
+		name               string
+		withAdminClaim     bool
+		withDeveloperClaim bool
+		customClaims       map[string]interface{} // 指定時はこのクレームでトークンをセット（403検証用）
+		wantCode           int
+		validate           func(t *testing.T, w *httptest.ResponseRecorder)
+	}{
+		{
+			name:           "正常にお知らせ一覧が取得できる",
+			withAdminClaim: true,
+			wantCode:       http.StatusOK,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err, "JSONのパースに失敗しました")
+
+				announcements, ok := response["announcements"].([]interface{})
+				assert.True(t, ok, "announcementsフィールドが配列ではありません")
+				assert.NotEmpty(t, announcements, "アナウンスメントが空です")
+			},
+		},
+		{
+			name:               "developerクレームのみでも一覧が取得できる",
+			withDeveloperClaim: true,
+			wantCode:           http.StatusOK,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err, "JSONのパースに失敗しました")
+				announcements, ok := response["announcements"].([]interface{})
+				assert.True(t, ok, "announcementsフィールドが配列ではありません")
+				assert.NotEmpty(t, announcements, "アナウンスメントが空です")
+				assert.Len(t, announcements, 1, "MockRepositoryは1件返すはずです")
+			},
+		},
+		{
+			name:           "Content-Typeがapplication/jsonである",
+			withAdminClaim: true,
+			wantCode:       http.StatusOK,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				assert.Equal(t, "application/json; charset=utf-8", w.Header().Get("Content-Type"))
+			},
+		},
+		{
+			name:           "レスポンスが正しい構造である",
+			withAdminClaim: true,
+			wantCode:       http.StatusOK,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+
+				announcements, ok := response["announcements"].([]interface{})
+				assert.True(t, ok, "announcementsフィールドが配列ではありません")
+				assert.Len(t, announcements, 1, "MockRepositoryは1件返すはずです")
+			},
+		},
+		{
+			name:           "お知らせのフィールドが正しく返される",
+			withAdminClaim: true,
+			wantCode:       http.StatusOK,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response struct {
+					Announcements []api.AnnouncementServiceAnnouncement `json:"announcements"`
+				}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Len(t, response.Announcements, 1, "MockRepositoryは1件返すはずです")
+				assert.Equal(t, "1", response.Announcements[0].Id)
+				assert.Equal(t, "お知らせ1", response.Announcements[0].Title)
+				assert.Equal(t, "https://example.com/1", response.Announcements[0].Url)
+			assert.False(t, response.Announcements[0].AvailableFrom.IsZero(), "AvailableFromが設定されていること")
+			assert.False(t, response.Announcements[0].AvailableUntil.IsZero(), "AvailableUntilが設定されていること")
+			},
+		},
+		{
+			name:           "認証トークンがない場合は401エラー",
+			withAdminClaim: false,
+			wantCode:       http.StatusUnauthorized,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Authentication required", response["error"])
+			},
+		},
+		{
+			name:         "admin/developer以外のクレームのみのトークンでは403エラー",
+			customClaims: map[string]interface{}{"user": true},
+			wantCode:     http.StatusForbidden,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Insufficient permissions", response["error"])
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mockRepo := repository.NewMockAnnouncementRepository()
+			announcementService := service.NewAnnouncementService(mockRepo)
+			h := handler.NewHandler(announcementService)
+			var w *httptest.ResponseRecorder
+			var c *gin.Context
+			if tt.customClaims != nil {
+				w, c = setupTestContextWithClaims(tt.customClaims)
+			} else if tt.withDeveloperClaim {
+				w, c = setupTestContextWithClaims(map[string]interface{}{"developer": true})
+			} else {
+				w, c = setupTestContext(tt.withAdminClaim)
+			}
+
+			h.AnnouncementsV1List(c)
+
+			assert.Equal(t, tt.wantCode, w.Code)
+
+			if tt.validate != nil {
+				tt.validate(t, w)
+			}
+		})
+	}
+}
+
+func TestAnnouncementsV1Detail(t *testing.T) {
+	tests := []struct {
+		name           string
+		id             string
+		withAdminClaim bool
+		customClaims   map[string]interface{} // 指定時はこのクレームでトークンをセット（403検証用）
+		wantCode       int
+		validate       func(t *testing.T, w *httptest.ResponseRecorder)
+	}{
+		{
+			name:           "正常にお知らせ詳細が取得できる",
+			id:             "1",
+			withAdminClaim: true,
+			wantCode:       http.StatusOK,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response struct {
+					Announcement api.AnnouncementServiceAnnouncement `json:"announcement"`
+				}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err, "JSONのパースに失敗しました")
+				assert.Equal(t, "1", response.Announcement.Id)
+				assert.Equal(t, "お知らせ1", response.Announcement.Title)
+				assert.Equal(t, "https://example.com/1", response.Announcement.Url)
+			},
+		},
+		{
+			name:           "認証トークンがない場合は401エラー",
+			id:             "1",
+			withAdminClaim: false,
+			wantCode:       http.StatusUnauthorized,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Authentication required", response["error"])
+			},
+		},
+		{
+			name:         "admin/developer以外のクレームのみのトークンでは403エラー",
+			id:           "1",
+			customClaims: map[string]interface{}{"user": true},
+			wantCode:     http.StatusForbidden,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Insufficient permissions", response["error"])
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mockRepo := repository.NewMockAnnouncementRepository()
+			announcementService := service.NewAnnouncementService(mockRepo)
+			h := handler.NewHandler(announcementService)
+			var w *httptest.ResponseRecorder
+			var c *gin.Context
+			if tt.customClaims != nil {
+				w, c = setupTestContextWithClaims(tt.customClaims)
+			} else {
+				w, c = setupTestContext(tt.withAdminClaim)
+			}
+
+			h.AnnouncementsV1Detail(c, tt.id)
+
+			assert.Equal(t, tt.wantCode, w.Code)
+
+			if tt.validate != nil {
+				tt.validate(t, w)
+			}
+		})
+	}
+}
+
+func TestAnnouncementsV1Create(t *testing.T) {
+	now := time.Now()
+	until := now.Add(24 * time.Hour)
+
+	tests := []struct {
+		name               string
+		request            api.AnnouncementServiceAnnouncementRequest
+		withAdminClaim     bool
+		withDeveloperClaim bool
+		customClaims       map[string]interface{} // 指定時はこのクレームでトークンをセット（403検証用）
+		wantCode           int
+		validate           func(t *testing.T, w *httptest.ResponseRecorder)
+	}{
+		{
+			name: "正常にお知らせを作成できる",
+			request: api.AnnouncementServiceAnnouncementRequest{
+				Title:          "新しいお知らせ",
+				Url:            "https://example.com/new",
+				AvailableFrom:  now,
+				AvailableUntil: &until,
+			},
+			withAdminClaim: true,
+			wantCode:       http.StatusCreated,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response struct {
+					Announcement api.AnnouncementServiceAnnouncement `json:"announcement"`
+				}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err, "JSONのパースに失敗しました")
+				assert.Equal(t, "created-id", response.Announcement.Id)
+				assert.Equal(t, "新しいお知らせ", response.Announcement.Title)
+				assert.Equal(t, "https://example.com/new", response.Announcement.Url)
+			},
+		},
+		{
+			name: "developerクレームのみでも作成できる",
+			request: api.AnnouncementServiceAnnouncementRequest{
+				Title:          "developer経由のお知らせ",
+				Url:            "https://example.com/developer",
+				AvailableFrom:  now,
+				AvailableUntil: &until,
+			},
+			withDeveloperClaim: true,
+			wantCode:           http.StatusCreated,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response struct {
+					Announcement api.AnnouncementServiceAnnouncement `json:"announcement"`
+				}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err, "JSONのパースに失敗しました")
+				assert.Equal(t, "created-id", response.Announcement.Id)
+				assert.Equal(t, "developer経由のお知らせ", response.Announcement.Title)
+				assert.Equal(t, "https://example.com/developer", response.Announcement.Url)
+			},
+		},
+		{
+			name: "認証トークンがない場合は401エラー",
+			request: api.AnnouncementServiceAnnouncementRequest{
+				Title:          "新しいお知らせ",
+				Url:            "https://example.com/new",
+				AvailableFrom:  now,
+				AvailableUntil: &until,
+			},
+			withAdminClaim: false,
+			wantCode:       http.StatusUnauthorized,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Authentication required", response["error"])
+			},
+		},
+		{
+			name: "admin/developer以外のクレームのみのトークンでは403エラー",
+			request: api.AnnouncementServiceAnnouncementRequest{
+				Title:          "新しいお知らせ",
+				Url:            "https://example.com/new",
+				AvailableFrom:  now,
+				AvailableUntil: &until,
+			},
+			customClaims: map[string]interface{}{"user": true},
+			wantCode:     http.StatusForbidden,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Insufficient permissions", response["error"])
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mockRepo := repository.NewMockAnnouncementRepository()
+			announcementService := service.NewAnnouncementService(mockRepo)
+			h := handler.NewHandler(announcementService)
+			var w *httptest.ResponseRecorder
+			var c *gin.Context
+			if tt.customClaims != nil {
+				w, c = setupTestContextWithClaims(tt.customClaims)
+			} else if tt.withDeveloperClaim {
+				w, c = setupTestContextWithClaims(map[string]interface{}{"developer": true})
+			} else {
+				w, c = setupTestContext(tt.withAdminClaim)
+			}
+
+			// リクエストボディを設定
+			body, err := json.Marshal(tt.request)
+			require.NoError(t, err, "リクエストボディのJSONエンコードに失敗しました")
+			c.Request = httptest.NewRequest(http.MethodPost, "/api/v1/announcements", bytes.NewBuffer(body))
+			c.Request.Header.Set("Content-Type", "application/json")
+
+			h.AnnouncementsV1Create(c)
+
+			assert.Equal(t, tt.wantCode, w.Code)
+
+			if tt.validate != nil {
+				tt.validate(t, w)
+			}
+		})
+	}
+}
+
+func TestAnnouncementsV1Update(t *testing.T) {
+	now := time.Now()
+	until := now.Add(24 * time.Hour)
+
+	tests := []struct {
+		name           string
+		id             string
+		request        api.AnnouncementServiceAnnouncementRequest
+		withAdminClaim bool
+		customClaims   map[string]interface{} // 指定時はこのクレームでトークンをセット（403検証用）
+		wantCode       int
+		validate       func(t *testing.T, w *httptest.ResponseRecorder)
+	}{
+		{
+			name: "正常にお知らせを更新できる",
+			id:   "1",
+			request: api.AnnouncementServiceAnnouncementRequest{
+				Title:          "更新されたお知らせ",
+				Url:            "https://example.com/updated",
+				AvailableFrom:  now,
+				AvailableUntil: &until,
+			},
+			withAdminClaim: true,
+			wantCode:       http.StatusOK,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response struct {
+					Announcement api.AnnouncementServiceAnnouncement `json:"announcement"`
+				}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err, "JSONのパースに失敗しました")
+				assert.Equal(t, "1", response.Announcement.Id)
+				assert.Equal(t, "更新されたお知らせ", response.Announcement.Title)
+				assert.Equal(t, "https://example.com/updated", response.Announcement.Url)
+			},
+		},
+		{
+			name: "認証トークンがない場合は401エラー",
+			id:   "1",
+			request: api.AnnouncementServiceAnnouncementRequest{
+				Title:          "更新されたお知らせ",
+				Url:            "https://example.com/updated",
+				AvailableFrom:  now,
+				AvailableUntil: &until,
+			},
+			withAdminClaim: false,
+			wantCode:       http.StatusUnauthorized,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Authentication required", response["error"])
+			},
+		},
+		{
+			name: "admin/developer以外のクレームのみのトークンでは403エラー",
+			id:   "1",
+			request: api.AnnouncementServiceAnnouncementRequest{
+				Title:          "更新されたお知らせ",
+				Url:            "https://example.com/updated",
+				AvailableFrom:  now,
+				AvailableUntil: &until,
+			},
+			customClaims: map[string]interface{}{"user": true},
+			wantCode:     http.StatusForbidden,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Insufficient permissions", response["error"])
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mockRepo := repository.NewMockAnnouncementRepository()
+			announcementService := service.NewAnnouncementService(mockRepo)
+			h := handler.NewHandler(announcementService)
+			var w *httptest.ResponseRecorder
+			var c *gin.Context
+			if tt.customClaims != nil {
+				w, c = setupTestContextWithClaims(tt.customClaims)
+			} else {
+				w, c = setupTestContext(tt.withAdminClaim)
+			}
+
+			// リクエストボディを設定
+			body, err := json.Marshal(tt.request)
+			require.NoError(t, err, "リクエストボディのJSONエンコードに失敗しました")
+			c.Request = httptest.NewRequest(http.MethodPut, "/api/v1/announcements/"+tt.id, bytes.NewBuffer(body))
+			c.Request.Header.Set("Content-Type", "application/json")
+
+			h.AnnouncementsV1Update(c, tt.id)
+
+			assert.Equal(t, tt.wantCode, w.Code)
+
+			if tt.validate != nil {
+				tt.validate(t, w)
+			}
+		})
+	}
+}
+
+func TestAnnouncementsV1Delete(t *testing.T) {
+	tests := []struct {
+		name               string
+		id                 string
+		withAdminClaim     bool
+		withDeveloperClaim bool
+		customClaims       map[string]interface{} // 指定時はこのクレームでトークンをセット（403検証用）
+		wantCode           int
+		validate           func(t *testing.T, w *httptest.ResponseRecorder)
+	}{
+		{
+			name:           "正常にお知らせを削除できる",
+			id:             "1",
+			withAdminClaim: true,
+			wantCode:       http.StatusNoContent,
+			validate:       nil,
+		},
+		{
+			name:               "developerクレームのみでも削除できる",
+			id:                 "1",
+			withDeveloperClaim: true,
+			wantCode:           http.StatusNoContent,
+			validate:           nil,
+		},
+		{
+			name:           "認証トークンがない場合は401エラー",
+			id:             "1",
+			withAdminClaim: false,
+			wantCode:       http.StatusUnauthorized,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Authentication required", response["error"])
+			},
+		},
+		{
+			name:         "admin/developer以外のクレームのみのトークンでは403エラー",
+			id:           "1",
+			customClaims: map[string]interface{}{"user": true},
+			wantCode:     http.StatusForbidden,
+			validate: func(t *testing.T, w *httptest.ResponseRecorder) {
+				var response map[string]interface{}
+				err := json.Unmarshal(w.Body.Bytes(), &response)
+				assert.NoError(t, err)
+				assert.Equal(t, "Insufficient permissions", response["error"])
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mockRepo := repository.NewMockAnnouncementRepository()
+			announcementService := service.NewAnnouncementService(mockRepo)
+			h := handler.NewHandler(announcementService)
+			var w *httptest.ResponseRecorder
+			var c *gin.Context
+			if tt.customClaims != nil {
+				w, c = setupTestContextWithClaims(tt.customClaims)
+			} else if tt.withDeveloperClaim {
+				w, c = setupTestContextWithClaims(map[string]interface{}{"developer": true})
+			} else {
+				w, c = setupTestContext(tt.withAdminClaim)
+			}
+
+			h.AnnouncementsV1Delete(c, tt.id)
+
+			assert.Equal(t, tt.wantCode, w.Code)
+
+			if tt.validate != nil {
+				tt.validate(t, w)
+			}
+		})
+	}
+}
diff --git a/internal/repository/announcement_mock.go b/internal/repository/announcement_mock.go
new file mode 100644
index 0000000..85bb253
--- /dev/null
+++ b/internal/repository/announcement_mock.go
@@ -0,0 +1,71 @@
+package repository
+
+import (
+	"context"
+	"time"
+
+	"github.com/fun-dotto/api-template/internal/domain"
+	"github.com/fun-dotto/api-template/internal/service"
+)
+
+type mockAnnouncementRepository struct{}
+
+// NewMockAnnouncementRepository モックリポジトリを作成する
+func NewMockAnnouncementRepository() service.AnnouncementRepository {
+	return &mockAnnouncementRepository{}
+}
+
+// List 一覧を取得する（モック）
+func (r *mockAnnouncementRepository) List(ctx context.Context) ([]domain.Announcement, error) {
+	now := time.Now()
+	until := now.Add(24 * time.Hour)
+	return []domain.Announcement{
+		{
+			ID:             "1",
+			Title:          "お知らせ1",
+			URL:            "https://example.com/1",
+			AvailableFrom:  now,
+			AvailableUntil: &until,
+		},
+	}, nil
+}
+
+// Detail 詳細を取得する（モック）
+func (r *mockAnnouncementRepository) Detail(ctx context.Context, id string) (*domain.Announcement, error) {
+	now := time.Now()
+	until := now.Add(24 * time.Hour)
+	return &domain.Announcement{
+		ID:             id,
+		Title:          "お知らせ" + id,
+		URL:            "https://example.com/" + id,
+		AvailableFrom:  now,
+		AvailableUntil: &until,
+	}, nil
+}
+
+// Create 新規作成する（モック）
+func (r *mockAnnouncementRepository) Create(ctx context.Context, req *domain.AnnouncementRequest) (*domain.Announcement, error) {
+	return &domain.Announcement{
+		ID:             "created-id",
+		Title:          req.Title,
+		URL:            req.URL,
+		AvailableFrom:  req.AvailableFrom,
+		AvailableUntil: req.AvailableUntil,
+	}, nil
+}
+
+// Update 更新する（モック）
+func (r *mockAnnouncementRepository) Update(ctx context.Context, id string, req *domain.AnnouncementRequest) (*domain.Announcement, error) {
+	return &domain.Announcement{
+		ID:             id,
+		Title:          req.Title,
+		URL:            req.URL,
+		AvailableFrom:  req.AvailableFrom,
+		AvailableUntil: req.AvailableUntil,
+	}, nil
+}
+
+// Delete 削除する（モック）
+func (r *mockAnnouncementRepository) Delete(ctx context.Context, id string) error {
+	return nil
+}