diff --git a/internal/api/client/lists/listaccountsadd_test.go b/internal/api/client/lists/listaccountsadd_test.go
new file mode 100644
index 000000000..492996882
--- /dev/null
+++ b/internal/api/client/lists/listaccountsadd_test.go
@@ -0,0 +1,126 @@
+// GoToSocial
+// Copyright (C) GoToSocial Authors admin@gotosocial.org
+// SPDX-License-Identifier: AGPL-3.0-or-later
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package lists_test
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"codeberg.org/gruf/go-bytes"
+	"github.com/stretchr/testify/suite"
+	"github.com/superseriousbusiness/gotosocial/internal/api/client/lists"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+	"github.com/superseriousbusiness/gotosocial/testrig"
+)
+
+type ListAccountsAddTestSuite struct {
+	ListsStandardTestSuite
+}
+
+func (suite *ListAccountsAddTestSuite) postListAccounts(
+	expectedHTTPStatus int,
+	listID string,
+	accountIDs []string,
+) ([]byte, error) {
+	var (
+		recorder = httptest.NewRecorder()
+		ctx, _   = testrig.CreateGinTestContext(recorder, nil)
+	)
+
+	// Prepare test context.
+	ctx.Set(oauth.SessionAuthorizedAccount, suite.testAccounts["local_account_1"])
+	ctx.Set(oauth.SessionAuthorizedToken, oauth.DBTokenToToken(suite.testTokens["local_account_1"]))
+	ctx.Set(oauth.SessionAuthorizedApplication, suite.testApplications["application_1"])
+	ctx.Set(oauth.SessionAuthorizedUser, suite.testUsers["local_account_1"])
+
+	// Inject path parameters.
+	ctx.AddParam("id", listID)
+
+	// Inject query parameters.
+	requestPath := config.GetProtocol() + "://" + config.GetHost() + "/api/" + lists.BasePath + "/" + listID + "/accounts"
+
+	// Prepare test body.
+	buf, w, err := testrig.CreateMultipartFormData("", "", map[string][]string{
+		"account_ids[]": accountIDs,
+	})
+
+	// Prepare test context request.
+	request := httptest.NewRequest(http.MethodPost, requestPath, bytes.NewReader(buf.Bytes()))
+	request.Header.Set("accept", "application/json")
+	request.Header.Set("content-type", w.FormDataContentType())
+	ctx.Request = request
+
+	// trigger the handler
+	suite.listsModule.ListAccountsPOSTHandler(ctx)
+
+	// read the response
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	// Check status code.
+	if status := recorder.Code; expectedHTTPStatus != status {
+		err = fmt.Errorf("expected %d got %d", expectedHTTPStatus, status)
+	}
+
+	return b, err
+}
+
+func (suite *ListAccountsAddTestSuite) TestPostListAccountNotFollowed() {
+	listID := suite.testLists["local_account_1_list_1"].ID
+	accountIDs := []string{
+		suite.testAccounts["remote_account_1"].ID,
+	}
+
+	resp, err := suite.postListAccounts(http.StatusNotFound, listID, accountIDs)
+	suite.NoError(err)
+	suite.Equal(`{"error":"Not Found: you do not follow account 01F8MH5ZK5VRH73AKHQM6Y9VNX"}`, string(resp))
+}
+
+func (suite *ListAccountsAddTestSuite) TestPostListAccountOK() {
+	// Remove turtle from the list.
+	if err := suite.db.DeleteListEntry(
+		context.Background(),
+		suite.testListEntries["local_account_1_list_1_entry_1"].ID,
+	); err != nil {
+		suite.FailNow(err.Error())
+	}
+
+	// Add turtle back to the list.
+	listID := suite.testLists["local_account_1_list_1"].ID
+	accountIDs := []string{
+		suite.testAccounts["local_account_2"].ID,
+	}
+
+	resp, err := suite.postListAccounts(http.StatusOK, listID, accountIDs)
+	suite.NoError(err)
+	suite.Equal(`{}`, string(resp))
+}
+
+func TestListAccountsAddTestSuite(t *testing.T) {
+	suite.Run(t, new(ListAccountsAddTestSuite))
+}
diff --git a/internal/api/client/lists/lists_test.go b/internal/api/client/lists/lists_test.go
index e7e56183e..8504f7ee2 100644
--- a/internal/api/client/lists/lists_test.go
+++ b/internal/api/client/lists/lists_test.go
@@ -55,6 +55,7 @@ type ListsStandardTestSuite struct {
 	testEmojis          map[string]*gtsmodel.Emoji
 	testEmojiCategories map[string]*gtsmodel.EmojiCategory
 	testLists           map[string]*gtsmodel.List
+	testListEntries     map[string]*gtsmodel.ListEntry
 
 	// module being tested
 	listsModule *lists.Module
@@ -71,6 +72,7 @@ func (suite *ListsStandardTestSuite) SetupSuite() {
 	suite.testEmojis = testrig.NewTestEmojis()
 	suite.testEmojiCategories = testrig.NewTestEmojiCategories()
 	suite.testLists = testrig.NewTestLists()
+	suite.testListEntries = testrig.NewTestListEntries()
 }
 
 func (suite *ListsStandardTestSuite) SetupTest() {