test(handlers/delegation): add coverage for listDelegationsFromLedger + listDelegationsFromActivityLogs

Add 13 unit tests covering the data-backend methods behind ListDelegations:

- listDelegationsFromLedger (7 cases): empty result → nil, single row,
  multiple rows in order, NULL last_heartbeat/deadline/result_preview/error_detail
  omitted from map, query error → nil (graceful fallback), rows.Err() mid-stream,
  scan error on row → row skipped.

- listDelegationsFromActivityLogs (6 cases): empty → empty slice, single
  delegate row, delegate_result row with error+response_preview+delegation_id,
  query error → empty slice, rows.Err(), scan error → row skipped.

Both methods were untested (cf. infra-sre review of PR #942 noting
listDelegationsFromLedger had no test coverage). Uses sqlmock, follows
existing test patterns in delegation_test.go.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace-server/internal/handlers/delegation_list_test.go

@@ -0,0 +1,493 @@
+package handlers
+
+// delegation_list_test.go — unit tests for listDelegationsFromLedger and
+// listDelegationsFromActivityLogs. Both methods are the data-backend of the
+// ListDelegations handler; coverage was missing (cf. infra-sre review of PR #942).
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/DATA-DOG/go-sqlmock"
+)
+
+// ---------- listDelegationsFromLedger ----------
+
+// Columns in the delegations table (SELECT order must match the query).
+const ledgerCols = "delegation_id, caller_id, callee_id, task_preview, " +
+	"status, result_preview, error_detail, last_heartbeat, deadline, created_at, updated_at"
+
+func TestListDelegationsFromLedger_EmptyResult(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	rows := sqlmock.NewRows([]string{})
+	mock.ExpectQuery("SELECT .+ FROM delegations").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromLedger(context.Background(), "ws-1")
+	if got != nil {
+		t.Errorf("empty result: expected nil, got %v", got)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromLedger_SingleRow(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	rows := sqlmock.NewRows([]string{}).AddRow(
+		"del-1", "ws-1", "ws-2", "summarise the report",
+		"completed", "the report is about Q1",
+		"", now, now, now, now,
+	)
+	mock.ExpectQuery("SELECT .+ FROM delegations").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromLedger(context.Background(), "ws-1")
+	if len(got) != 1 {
+		t.Fatalf("expected 1 entry, got %d", len(got))
+	}
+	e := got[0]
+	if e["delegation_id"] != "del-1" {
+		t.Errorf("delegation_id: got %v, want del-1", e["delegation_id"])
+	}
+	if e["source_id"] != "ws-1" {
+		t.Errorf("source_id: got %v, want ws-1", e["source_id"])
+	}
+	if e["target_id"] != "ws-2" {
+		t.Errorf("target_id: got %v, want ws-2", e["target_id"])
+	}
+	if e["status"] != "completed" {
+		t.Errorf("status: got %v, want completed", e["status"])
+	}
+	if e["response_preview"] != "the report is about Q1" {
+		t.Errorf("response_preview: got %v", e["response_preview"])
+	}
+	if _, ok := e["error"]; ok {
+		t.Errorf("error should be absent when empty, got %v", e["error"])
+	}
+	if e["_ledger"] != true {
+		t.Errorf("_ledger marker: got %v, want true", e["_ledger"])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromLedger_MultipleRows(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	rows := sqlmock.NewRows([]string{}).
+		AddRow("del-a", "ws-1", "ws-2", "task a", "in_progress", "", "", now, now, now, now).
+		AddRow("del-b", "ws-1", "ws-3", "task b", "failed", "", "timeout", now, now, now, now).
+		AddRow("del-c", "ws-1", "ws-4", "task c", "completed", "result c", "", now, now, now, now)
+	mock.ExpectQuery("SELECT .+ FROM delegations").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromLedger(context.Background(), "ws-1")
+	if len(got) != 3 {
+		t.Fatalf("expected 3 entries, got %d", len(got))
+	}
+	if got[0]["delegation_id"] != "del-a" || got[1]["delegation_id"] != "del-b" || got[2]["delegation_id"] != "del-c" {
+		t.Errorf("unexpected order: %v", got)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromLedger_NullsOmitted(t *testing.T) {
+	// last_heartbeat, deadline, result_preview, error_detail are all NULL.
+	// Handler must not panic and must omit those keys from the map.
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	rows := sqlmock.NewRows([]string{}).
+		AddRow("del-1", "ws-1", "ws-2", "task", "queued", nil, nil, nil, nil, now, now)
+	mock.ExpectQuery("SELECT .+ FROM delegations").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromLedger(context.Background(), "ws-1")
+	if len(got) != 1 {
+		t.Fatalf("expected 1 entry, got %d", len(got))
+	}
+	e := got[0]
+	if _, ok := e["last_heartbeat"]; ok {
+		t.Error("last_heartbeat should be absent when NULL")
+	}
+	if _, ok := e["deadline"]; ok {
+		t.Error("deadline should be absent when NULL")
+	}
+	if _, ok := e["response_preview"]; ok {
+		t.Error("response_preview should be absent when NULL result_preview")
+	}
+	if _, ok := e["error"]; ok {
+		t.Error("error should be absent when NULL error_detail")
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromLedger_QueryError(t *testing.T) {
+	// Query failure returns nil — graceful fallback, no panic.
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	mock.ExpectQuery("SELECT .+ FROM delegations").
+		WithArgs("ws-1").
+		WillReturnError(context.DeadlineExceeded)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromLedger(context.Background(), "ws-1")
+	if got != nil {
+		t.Errorf("query error: expected nil, got %v", got)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromLedger_RowsErr(t *testing.T) {
+	// rows.Err() mid-stream: log but return partial results collected so far.
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	rows := sqlmock.NewRows([]string{}).
+		RowError(0, context.DeadlineExceeded). // error on first row
+		AddRow("del-1", "ws-1", "ws-2", "task", "queued", "", "", now, now, now, now)
+	mock.ExpectQuery("SELECT .+ FROM delegations").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromLedger(context.Background(), "ws-1")
+	// rows.Err() is logged but partial results may still be returned
+	// (the handler does NOT abort on rows.Err — it logs and returns what it has)
+	if got == nil {
+		t.Error("rows.Err path should still return partial results")
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromLedger_ScanError(t *testing.T) {
+	// Scan error on a row: handler skips that row and continues.
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	// Wrong column count → scan error
+	badRows := sqlmock.NewRows([]string{}).AddRow("only-one-col")
+	goodRows := sqlmock.NewRows([]string{}).
+		AddRow("del-1", "ws-1", "ws-2", "task", "queued", "", "", now, now, now, now)
+	mock.ExpectQuery("SELECT .+ FROM delegations").
+		WithArgs("ws-1").
+		WillReturnRows(badRows, goodRows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromLedger(context.Background(), "ws-1")
+	// Bad row is skipped; good row is returned.
+	if len(got) != 1 {
+		t.Fatalf("expected 1 entry after scan skip, got %d", len(got))
+	}
+	if got[0]["delegation_id"] != "del-1" {
+		t.Errorf("unexpected entry: %v", got[0])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+// ---------- listDelegationsFromActivityLogs ----------
+
+// Columns in the activity_logs query.
+const activityCols = "id, activity_type, " +
+	"COALESCE(source_id::text, ''), COALESCE(target_id::text, ''), " +
+	"COALESCE(summary, ''), COALESCE(status, ''), COALESCE(error_detail, ''), " +
+	"COALESCE(response_body->>'text', response_body::text, ''), " +
+	"COALESCE(request_body->>'delegation_id', response_body->>'delegation_id', ''), " +
+	"created_at"
+
+func TestListDelegationsFromActivityLogs_EmptyResult(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	rows := sqlmock.NewRows([]string{})
+	mock.ExpectQuery("SELECT .+ FROM activity_logs").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromActivityLogs(context.Background(), "ws-1")
+	if len(got) != 0 {
+		t.Errorf("empty result: expected empty slice, got %v", got)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromActivityLogs_SingleDelegateRow(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	rows := sqlmock.NewRows([]string{}).AddRow(
+		"act-1", "delegate",
+		"ws-1", "ws-2",
+		"analyse Q1 numbers",
+		"in_progress",
+		"", "", "",
+		now,
+	)
+	mock.ExpectQuery("SELECT .+ FROM activity_logs").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromActivityLogs(context.Background(), "ws-1")
+	if len(got) != 1 {
+		t.Fatalf("expected 1 entry, got %d", len(got))
+	}
+	e := got[0]
+	if e["id"] != "act-1" {
+		t.Errorf("id: got %v, want act-1", e["id"])
+	}
+	if e["type"] != "delegate" {
+		t.Errorf("type: got %v, want delegate", e["type"])
+	}
+	if e["source_id"] != "ws-1" {
+		t.Errorf("source_id: got %v, want ws-1", e["source_id"])
+	}
+	if e["target_id"] != "ws-2" {
+		t.Errorf("target_id: got %v, want ws-2", e["target_id"])
+	}
+	if e["summary"] != "analyse Q1 numbers" {
+		t.Errorf("summary: got %v", e["summary"])
+	}
+	if e["status"] != "in_progress" {
+		t.Errorf("status: got %v", e["status"])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromActivityLogs_DelegateResultWithError(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	rows := sqlmock.NewRows([]string{}).AddRow(
+		"act-2", "delegate_result",
+		"ws-1", "ws-2",
+		"result summary",
+		"failed",
+		"Callee workspace not reachable",
+		"the result body text",
+		"del-abc",
+		now,
+	)
+	mock.ExpectQuery("SELECT .+ FROM activity_logs").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromActivityLogs(context.Background(), "ws-1")
+	if len(got) != 1 {
+		t.Fatalf("expected 1 entry, got %d", len(got))
+	}
+	e := got[0]
+	if e["type"] != "delegate_result" {
+		t.Errorf("type: got %v", e["type"])
+	}
+	if e["error"] != "Callee workspace not reachable" {
+		t.Errorf("error: got %v", e["error"])
+	}
+	if e["response_preview"] != "the result body text" {
+		t.Errorf("response_preview: got %v", e["response_preview"])
+	}
+	if e["delegation_id"] != "del-abc" {
+		t.Errorf("delegation_id: got %v", e["delegation_id"])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromActivityLogs_QueryError(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	mock.ExpectQuery("SELECT .+ FROM activity_logs").
+		WithArgs("ws-1").
+		WillReturnError(context.DeadlineExceeded)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromActivityLogs(context.Background(), "ws-1")
+	// Error → returns empty slice, not nil.
+	if len(got) != 0 {
+		t.Errorf("query error: expected empty slice, got %v", got)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromActivityLogs_RowsErr(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	rows := sqlmock.NewRows([]string{}).
+		RowError(0, context.DeadlineExceeded).
+		AddRow("act-1", "delegate", "ws-1", "ws-2", "task", "queued", "", "", "", now)
+	mock.ExpectQuery("SELECT .+ FROM activity_logs").
+		WithArgs("ws-1").
+		WillReturnRows(rows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromActivityLogs(context.Background(), "ws-1")
+	if got == nil {
+		t.Error("rows.Err path should not return nil")
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}
+
+func TestListDelegationsFromActivityLogs_ScanErrorSkipped(t *testing.T) {
+	mockDB, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatalf("failed to create sqlmock: %v", err)
+	}
+	defer mockDB.Close()
+	db.DB = mockDB
+
+	now := time.Now()
+	// Wrong column count → scan error on first row
+	badRows := sqlmock.NewRows([]string{}).AddRow("only-one")
+	goodRows := sqlmock.NewRows([]string{}).
+		AddRow("act-1", "delegate", "ws-1", "ws-2", "task", "queued", "", "", "", now)
+	mock.ExpectQuery("SELECT .+ FROM activity_logs").
+		WithArgs("ws-1").
+		WillReturnRows(badRows, goodRows)
+
+	broadcaster := newTestBroadcaster()
+	wh := NewWorkspaceHandler(broadcaster, nil, "http://localhost:8080", t.TempDir())
+	dh := NewDelegationHandler(wh, broadcaster)
+
+	got := dh.listDelegationsFromActivityLogs(context.Background(), "ws-1")
+	if len(got) != 1 {
+		t.Fatalf("expected 1 entry after scan skip, got %d", len(got))
+	}
+	if got[0]["id"] != "act-1" {
+		t.Errorf("unexpected entry: %v", got[0])
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Errorf("sqlmock expectations: %v", err)
+	}
+}