diff --git a/tests/csapi/account_data_test.go b/tests/csapi/account_data_test.go
new file mode 100644
index 00000000..1490896b
--- /dev/null
+++ b/tests/csapi/account_data_test.go
@@ -0,0 +1,67 @@
+package csapi_tests
+
+import (
+	"testing"
+
+	"github.com/matrix-org/complement/internal/b"
+	"github.com/matrix-org/complement/internal/match"
+	"github.com/matrix-org/complement/internal/must"
+)
+
+func TestAddAccountData(t *testing.T) {
+	deployment := Deploy(t, b.BlueprintOneToOneRoom)
+	defer deployment.Destroy(t)
+
+	alice := deployment.Client(t, "hs1", "@alice:hs1")
+
+	// sytest: Can add account data
+	// sytest: Can get account data without syncing
+	t.Run("Can add global account data", func(t *testing.T) {
+		// Set the account data entry
+		alice.SetGlobalAccountData(t, "test.key", map[string]interface{}{"value": "first"})
+
+		// check that getting the account data returns the correct value
+		must.MatchResponse(t, alice.GetGlobalAccountData(t, "test.key"), match.HTTPResponse{
+			JSON: []match.JSON{
+				match.JSONKeyEqual("value", "first"),
+			},
+		})
+
+		// Set it to something else
+		alice.SetGlobalAccountData(t, "test.key", map[string]interface{}{"value": "second"})
+
+		// check that getting the account data returns the updated value
+		must.MatchResponse(t, alice.GetGlobalAccountData(t, "test.key"), match.HTTPResponse{
+			JSON: []match.JSON{
+				match.JSONKeyEqual("value", "second"),
+			},
+		})
+	})
+
+	// sytest: Can add account data to room
+	// sytest: Can get room account data without syncing
+	t.Run("Can add room account data", func(t *testing.T) {
+		// Create a room
+		roomID := alice.CreateRoom(t, map[string]interface{}{})
+
+		// Set the room account data entry
+		alice.SetRoomAccountData(t, roomID, "test.key", map[string]interface{}{"value": "room first"})
+
+		// check that getting the account data returns the correct value
+		must.MatchResponse(t, alice.GetRoomAccountData(t, roomID, "test.key"), match.HTTPResponse{
+			JSON: []match.JSON{
+				match.JSONKeyEqual("value", "room first"),
+			},
+		})
+
+		// Set it to something else
+		alice.SetRoomAccountData(t, roomID, "test.key", map[string]interface{}{"value": "room second"})
+
+		// check that getting the account data returns the updated value
+		must.MatchResponse(t, alice.GetRoomAccountData(t, roomID, "test.key"), match.HTTPResponse{
+			JSON: []match.JSON{
+				match.JSONKeyEqual("value", "room second"),
+			},
+		})
+	})
+}