Re-vendor the shared files from sneak/prompts at 0653579 (closes #52)

Takes .golangci.yml, .dockerignore, .gitignore, .editorconfig, the
workflow and REPO_POLICIES.md from sneak/prompts 0653579, with this
repository's own entries after the shared content. Lint (golangci-lint
v2.14.0) and test are Dockerfile phases that script/lint and script/test
build alone with a new CACHEBUST value, keeping Go's and golangci-lint's
caches; the image build depends on both. make fmt and make fmt-check also
format the markdown with prettier, pinned in yarn.lock. The agent
guidance moves to AGENTS.md. The Go code is fixed for what the new
configuration finds, and the AS and prefix detail reads now return the
rows' error after their loops.

Model: opus-5-5

internal/server/handlers_internal_test.go

@@ -0,0 +1,667 @@
+package server
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"html"
+	"net/http"
+	"net/http/httptest"
+	"runtime"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"git.eeqj.de/sneak/routewatch/internal/config"
+	"git.eeqj.de/sneak/routewatch/internal/database"
+	"git.eeqj.de/sneak/routewatch/internal/logger"
+	"git.eeqj.de/sneak/routewatch/internal/metrics"
+	"git.eeqj.de/sneak/routewatch/internal/streamer"
+	"git.eeqj.de/sneak/routewatch/pkg/asinfo"
+	"github.com/google/uuid"
+)
+
+// The prefix and peer addresses the prefix page tests store routes for.
+const (
+	testPrefixV4 = "192.0.2.0/24"
+	testPeerV4   = "198.51.100.1"
+	testPeerV6   = "2001:db8::1"
+)
+
+// The names the stats handler tests report the two stats handlers by.
+const (
+	statusJSONHandlerName = "status.json"
+	statsHandlerName      = "stats"
+)
+
+// blockingStatsDB embeds database.Store (left nil) and overrides only
+// GetStatsContext, which blocks until release is closed. The stats handlers
+// call it in a goroutine; every other Store method is unused on the timeout
+// path and would panic if called.
+type blockingStatsDB struct {
+	database.Store
+
+	release chan struct{}
+}
+
+func (d blockingStatsDB) GetStatsContext(_ context.Context) (database.Stats, error) {
+	<-d.release
+
+	return database.Stats{}, nil
+}
+
+// TestStatsHandlersDoNotLeakOnTimeout drives each stats handler repeatedly with
+// a request whose context times out before the database responds, then releases
+// the blocked queries and asserts the goroutine count returns to its starting
+// value. Before the fix the per-request goroutine sent on an unbuffered channel
+// that nothing received once the timeout won, so it blocked forever and every
+// poll leaked one goroutine.
+//
+//nolint:paralleltest // counts goroutines, so no other test may run alongside
+func TestStatsHandlersDoNotLeakOnTimeout(t *testing.T) {
+	release := make(chan struct{})
+	db := blockingStatsDB{release: release}
+	s := New(db, streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
+
+	handlers := map[string]http.HandlerFunc{
+		statusJSONHandlerName: s.handleStatusJSON(),
+		statsHandlerName:      s.handleStats(),
+	}
+
+	baseline := settledGoroutineCount()
+
+	const (
+		iterations     = 20
+		requestTimeout = 50 * time.Millisecond
+	)
+	for _, handler := range handlers {
+		for range iterations {
+			ctx, cancel := context.WithTimeout(context.Background(), requestTimeout)
+			req := httptest.NewRequestWithContext(ctx, http.MethodGet, "/", nil)
+			handler(httptest.NewRecorder(), req)
+			cancel()
+		}
+	}
+
+	// Let the blocked queries finish; with buffered channels each goroutine's
+	// send now succeeds and the goroutine exits.
+	close(release)
+
+	if !waitForGoroutines(baseline) {
+		t.Fatalf("goroutines did not return to baseline %d, got %d",
+			baseline, runtime.NumGoroutine())
+	}
+}
+
+// TestStatsHandlersAnswerFromMemory checks that both stats handlers answer 200
+// with the live route counts and the prefix distribution while the database is
+// closed, so that any query would fail: the request path reads them from
+// memory. The prefix distribution query it used to run read every live route
+// and, on a large database, took the whole 4-second deadline, so
+// /api/v1/stats answered 500 (https://git.eeqj.de/sneak/routewatch/issues/30).
+// The oldest and newest route times still come from one-row lookups at the ends
+// of an index; with the database closed they are left out of the answer.
+func TestStatsHandlersAnswerFromMemory(t *testing.T) {
+	t.Parallel()
+
+	db, err := database.New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("database.New: %v", err)
+	}
+
+	ts := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+
+	err = db.UpsertLiveRouteBatch([]*database.LiveRoute{
+		{
+			ID: uuid.New(), Prefix: "198.51.100.0/24", MaskLength: 24, IPVersion: 4,
+			OriginASN: 64500, PeerIP: "192.0.2.1", ASPath: []int{64500},
+			NextHop: "192.0.2.1", LastUpdated: ts,
+		},
+		{
+			ID: uuid.New(), Prefix: "2001:db8::/32", MaskLength: 32, IPVersion: 6,
+			OriginASN: 64501, PeerIP: testPeerV6, ASPath: []int{64501},
+			NextHop: testPeerV6, LastUpdated: ts,
+		},
+	})
+	if err != nil {
+		t.Fatalf("UpsertLiveRouteBatch: %v", err)
+	}
+
+	err = db.Close()
+	if err != nil {
+		t.Fatalf("Close: %v", err)
+	}
+
+	s := New(db, streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
+	handlers := map[string]http.HandlerFunc{
+		statusJSONHandlerName: s.handleStatusJSON(),
+		statsHandlerName:      s.handleStats(),
+	}
+
+	for name, handler := range handlers {
+		rec := httptest.NewRecorder()
+		handler(rec, httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil))
+
+		if rec.Code != http.StatusOK {
+			t.Errorf("%s: status %d, want %d; body %s",
+				name, rec.Code, http.StatusOK, rec.Body)
+
+			continue
+		}
+
+		//nolint:tagliatelle // field names are the existing JSON API
+		var body struct {
+			Data struct {
+				IPv4Routes       int                           `json:"ipv4_routes"`
+				IPv6Routes       int                           `json:"ipv6_routes"`
+				IPv4Distribution []database.PrefixDistribution `json:"ipv4_prefix_distribution"`
+				IPv6Distribution []database.PrefixDistribution `json:"ipv6_prefix_distribution"`
+			} `json:"data"`
+		}
+
+		err := json.Unmarshal(rec.Body.Bytes(), &body)
+		if err != nil {
+			t.Fatalf("%s: decoding the answer: %v", name, err)
+		}
+
+		if body.Data.IPv4Routes != 1 || body.Data.IPv6Routes != 1 {
+			t.Errorf("%s: routes = (v4 %d, v6 %d), want (1, 1)",
+				name, body.Data.IPv4Routes, body.Data.IPv6Routes)
+		}
+
+		wantV4 := []database.PrefixDistribution{{MaskLength: 24, Count: 1}}
+		if !slices.Equal(body.Data.IPv4Distribution, wantV4) {
+			t.Errorf("%s: IPv4 distribution = %v, want %v",
+				name, body.Data.IPv4Distribution, wantV4)
+		}
+
+		wantV6 := []database.PrefixDistribution{{MaskLength: 32, Count: 1}}
+		if !slices.Equal(body.Data.IPv6Distribution, wantV6) {
+			t.Errorf("%s: IPv6 distribution = %v, want %v",
+				name, body.Data.IPv6Distribution, wantV6)
+		}
+	}
+}
+
+// TestPrefixDetailHandlersParsePrefix checks that both prefix pages find a
+// stored route whatever valid text form the URL writes its prefix in, and
+// answer 400 for a prefix that does not parse. The tables store the form
+// net/netip prints. Before the fix the URL text was looked up as typed, so
+// "2001:DB8:0:0::/32" was not found although "2001:db8::/32" was stored, and
+// "foo/24" answered 500 (https://git.eeqj.de/sneak/routewatch/issues/71).
+func TestPrefixDetailHandlersParsePrefix(t *testing.T) {
+	t.Parallel()
+
+	db, err := database.New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("database.New: %v", err)
+	}
+
+	t.Cleanup(func() { _ = db.Close() })
+
+	ts := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+
+	err = db.UpsertLiveRouteBatch([]*database.LiveRoute{
+		{
+			ID: uuid.New(), Prefix: testPrefixV4, MaskLength: 24, IPVersion: 4,
+			OriginASN: 64500, PeerIP: testPeerV4, ASPath: []int{64500},
+			NextHop: testPeerV4, LastUpdated: ts,
+		},
+		{
+			ID: uuid.New(), Prefix: "2001:db8::/32", MaskLength: 32, IPVersion: 6,
+			OriginASN: 64501, PeerIP: testPeerV6, ASPath: []int{64501},
+			NextHop: testPeerV6, LastUpdated: ts,
+		},
+	})
+	if err != nil {
+		t.Fatalf("UpsertLiveRouteBatch: %v", err)
+	}
+
+	s := New(db, streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
+
+	tests := []struct {
+		path string
+		want int
+	}{
+		{"/api/v1/prefix/foo/24", http.StatusBadRequest},
+		{"/prefix/foo/24", http.StatusBadRequest},
+		{"/api/v1/prefix/2001:DB8:0:0::/32", http.StatusOK},
+		{"/prefix/2001:DB8:0:0::/32", http.StatusOK},
+		{"/api/v1/prefix/192.0.2.1/24", http.StatusOK},
+		{"/prefix/192.0.2.1/24", http.StatusOK},
+	}
+
+	for _, tt := range tests {
+		rec := httptest.NewRecorder()
+		s.router.ServeHTTP(rec, httptest.NewRequestWithContext(
+			t.Context(), http.MethodGet, tt.path, nil))
+
+		if rec.Code != tt.want {
+			t.Errorf("%s: status %d, want %d; body %s",
+				tt.path, rec.Code, tt.want, rec.Body)
+		}
+	}
+}
+
+// errASDetailsLookupFailed is what failingASDetailsDB answers every AS details
+// lookup with.
+var errASDetailsLookupFailed = errors.New("AS details lookup failed")
+
+// failingASDetailsDB wraps a real store and fails every AS details lookup.
+type failingASDetailsDB struct {
+	database.Store
+}
+
+func (failingASDetailsDB) GetASDetailsContext(
+	_ context.Context, _ int,
+) (*database.ASN, []database.LiveRoute, error) {
+	return nil, nil, errASDetailsLookupFailed
+}
+
+// TestPrefixDetailShowsOriginNames checks that the prefix page shows each
+// origin AS's handle and description without looking up the AS's details,
+// which also read every route the AS originates. Before the fix the page did
+// that lookup once per origin, so with it failing the names were missing
+// (https://git.eeqj.de/sneak/routewatch/issues/67). The AS path column shows
+// handles too, so the test looks for the origin list's "(handle)" form.
+func TestPrefixDetailShowsOriginNames(t *testing.T) {
+	t.Parallel()
+
+	db, err := database.New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("database.New: %v", err)
+	}
+
+	t.Cleanup(func() { _ = db.Close() })
+
+	ts := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+	origins := []int{15169, 13335}
+
+	for _, asn := range origins {
+		_, err := db.GetOrCreateASN(asn, ts)
+		if err != nil {
+			t.Fatalf("GetOrCreateASN(%d): %v", asn, err)
+		}
+	}
+
+	err = db.UpsertLiveRouteBatch([]*database.LiveRoute{
+		{
+			ID: uuid.New(), Prefix: testPrefixV4, MaskLength: 24, IPVersion: 4,
+			OriginASN: origins[0], PeerIP: testPeerV4,
+			ASPath: []int{origins[0]}, NextHop: testPeerV4, LastUpdated: ts,
+		},
+		{
+			ID: uuid.New(), Prefix: testPrefixV4, MaskLength: 24, IPVersion: 4,
+			OriginASN: origins[1], PeerIP: "198.51.100.2",
+			ASPath: []int{origins[1]}, NextHop: "198.51.100.2", LastUpdated: ts,
+		},
+	})
+	if err != nil {
+		t.Fatalf("UpsertLiveRouteBatch: %v", err)
+	}
+
+	s := New(failingASDetailsDB{db}, streamer.New(logger.New(), metrics.New()),
+		logger.New(), &config.Config{})
+	rec := httptest.NewRecorder()
+	s.router.ServeHTTP(rec, httptest.NewRequestWithContext(
+		t.Context(), http.MethodGet, "/prefix/"+testPrefixV4, nil))
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status %d, want %d; body %s", rec.Code, http.StatusOK, rec.Body)
+	}
+
+	page := rec.Body.String()
+
+	for _, asn := range origins {
+		info, ok := asinfo.Get(asn)
+		if !ok {
+			t.Fatalf("AS%d is not in the AS info data", asn)
+		}
+
+		want := "(" + html.EscapeString(info.Handle) + ")"
+		if !strings.Contains(page, want) {
+			t.Errorf("page does not show AS%d's handle %q", asn, want)
+		}
+
+		want = html.EscapeString(info.Description)
+		if !strings.Contains(page, want) {
+			t.Errorf("page does not show AS%d's description %q", asn, want)
+		}
+	}
+}
+
+// shortRequestDeadline is the deadline the tests below give a request. The
+// server's 30-second limit and the stats handlers' 4-second limit inherit it,
+// so the tests do not wait for either.
+const shortRequestDeadline = 50 * time.Millisecond
+
+// TestRequestPastTimeLimitAnswers504 sends a request through the server's
+// router to a page and to a JSON route whose handlers wait for the time limit
+// to pass and return without answering. The page answers 504; the JSON route
+// answers 504 with the JSON error body. Before the fix both answered 408,
+// written by the time limit middleware from its own goroutine while the
+// handler could still be writing.
+func TestRequestPastTimeLimitAnswers504(t *testing.T) {
+	t.Parallel()
+
+	s := New(nil, streamer.New(logger.New(), metrics.New()), logger.New(),
+		&config.Config{})
+
+	waitForTimeLimit := func(_ http.ResponseWriter, r *http.Request) {
+		<-r.Context().Done()
+	}
+	// Registered the way setupRoutes registers pages and JSON routes.
+	s.router.Get("/slow-page", waitForTimeLimit)
+	s.router.Get("/slow.json",
+		JSONValidationMiddleware(http.HandlerFunc(waitForTimeLimit)).ServeHTTP)
+
+	tests := []struct {
+		path         string
+		wantJSONBody bool
+	}{
+		{path: "/slow-page"},
+		{path: "/slow.json", wantJSONBody: true},
+	}
+
+	for _, tt := range tests {
+		ctx, cancel := context.WithTimeout(context.Background(),
+			shortRequestDeadline)
+		rec := httptest.NewRecorder()
+		s.router.ServeHTTP(rec,
+			httptest.NewRequestWithContext(ctx, http.MethodGet, tt.path, nil))
+		cancel()
+
+		if rec.Code != http.StatusGatewayTimeout {
+			t.Errorf("%s: status %d, want %d; body %s",
+				tt.path, rec.Code, http.StatusGatewayTimeout, rec.Body)
+		}
+
+		if tt.wantJSONBody {
+			checkJSONErrorCode(t, tt.path, rec, http.StatusGatewayTimeout)
+		}
+	}
+}
+
+// TestStatsHandlersAnswer504WhenDatabaseReadRunsOut calls each stats handler
+// with a store that does not answer before the handler's 4-second limit runs
+// out, and checks that the handler itself answers 504 with the JSON error
+// body. Before the fix status.json answered 408, and /api/v1/stats wrote
+// nothing, which the JSON check on its route turned into 500.
+func TestStatsHandlersAnswer504WhenDatabaseReadRunsOut(t *testing.T) {
+	t.Parallel()
+
+	release := make(chan struct{})
+	defer close(release)
+
+	db := blockingStatsDB{release: release}
+	s := New(db, streamer.New(logger.New(), metrics.New()), logger.New(),
+		&config.Config{})
+
+	handlers := map[string]http.HandlerFunc{
+		statusJSONHandlerName: s.handleStatusJSON(),
+		statsHandlerName:      s.handleStats(),
+	}
+
+	for name, handler := range handlers {
+		ctx, cancel := context.WithTimeout(context.Background(),
+			shortRequestDeadline)
+		rec := httptest.NewRecorder()
+		handler(rec, httptest.NewRequestWithContext(ctx, http.MethodGet, "/", nil))
+		cancel()
+
+		if rec.Code != http.StatusGatewayTimeout {
+			t.Errorf("%s: status %d, want %d; body %s",
+				name, rec.Code, http.StatusGatewayTimeout, rec.Body)
+		}
+
+		checkJSONErrorCode(t, name, rec, http.StatusGatewayTimeout)
+	}
+}
+
+// slowDB embeds database.Store (left nil) and overrides the reads the routes
+// in TestRoutesAnswer504WhenDatabaseReadIsCutOff make. Each read waits until
+// its context ends and then answers as the real store does when the time
+// limit cuts it off: the IP read with the context's error, the prefix read
+// that there is no route, and the others with what they had read, here
+// nothing, and no error. Every other Store method is unused and would panic
+// if called.
+type slowDB struct {
+	database.Store
+}
+
+func (slowDB) GetStatsContext(ctx context.Context) (database.Stats, error) {
+	<-ctx.Done()
+
+	return database.Stats{}, nil
+}
+
+func (slowDB) GetIPInfoContext(
+	ctx context.Context, _ string,
+) (*database.IPInfo, error) {
+	<-ctx.Done()
+
+	return nil, ctx.Err()
+}
+
+func (slowDB) GetASDetailsContext(
+	ctx context.Context, asn int,
+) (*database.ASN, []database.LiveRoute, error) {
+	<-ctx.Done()
+
+	return &database.ASN{ASN: asn}, nil, nil
+}
+
+func (slowDB) GetPrefixDetailsContext(
+	ctx context.Context, _ string,
+) ([]database.LiveRoute, map[int]database.ASN, error) {
+	<-ctx.Done()
+
+	return nil, nil, database.ErrNoRoute
+}
+
+func (slowDB) GetRandomPrefixesByLengthContext(
+	ctx context.Context, _, _, _ int,
+) ([]database.LiveRoute, error) {
+	<-ctx.Done()
+
+	return nil, nil
+}
+
+// TestRoutesAnswer504WhenDatabaseReadIsCutOff sends a request through the
+// server's router for each route that reads the database, with a store whose
+// reads are cut off when the request's time limit passes. Each route answers
+// 504 with the time limit message. Without its check after the read, a route
+// answers with what the cut-off read returned: 500, 404, 200, or, on a page
+// that stops before rendering once the request has ended, 504 with an empty
+// body. The health check is left out: it answers 503 when its own 2-second
+// ping runs out.
+func TestRoutesAnswer504WhenDatabaseReadIsCutOff(t *testing.T) {
+	t.Parallel()
+
+	s := New(slowDB{}, streamer.New(logger.New(), metrics.New()), logger.New(),
+		&config.Config{})
+
+	tests := []struct {
+		path         string
+		wantJSONBody bool
+	}{
+		{path: "/as/64500"},
+		{path: "/prefix/192.0.2.0/24"},
+		{path: "/prefixlength/24"},
+		{path: "/prefixlength6/48"},
+		{path: "/status.json", wantJSONBody: true},
+		{path: "/ip/192.0.2.1", wantJSONBody: true},
+		{path: "/api/v1/stats", wantJSONBody: true},
+		{path: "/api/v1/ip/192.0.2.1", wantJSONBody: true},
+		{path: "/api/v1/as/64500", wantJSONBody: true},
+		{path: "/api/v1/prefix/192.0.2.0/24", wantJSONBody: true},
+	}
+
+	for _, tt := range tests {
+		checkRouteAnswers504(t, s, tt.path, tt.wantJSONBody)
+	}
+}
+
+// slowSecondReadDB embeds database.Store (left nil) and overrides the reads
+// of the routes that read the database twice. The first read answers at once;
+// the second, the AS page's peers read or the stats routes' WHOIS read, waits
+// until its context ends and then answers with the context's error, as the
+// real store does.
+type slowSecondReadDB struct {
+	database.Store
+}
+
+func (slowSecondReadDB) GetASDetailsContext(
+	_ context.Context, asn int,
+) (*database.ASN, []database.LiveRoute, error) {
+	return &database.ASN{ASN: asn}, nil, nil
+}
+
+func (slowSecondReadDB) GetASPeersContext(
+	ctx context.Context, _ int,
+) ([]database.ASPeer, error) {
+	<-ctx.Done()
+
+	return nil, ctx.Err()
+}
+
+func (slowSecondReadDB) GetStatsContext(_ context.Context) (database.Stats, error) {
+	return database.Stats{}, nil
+}
+
+func (slowSecondReadDB) GetWHOISStats(
+	ctx context.Context, _ time.Duration,
+) (*database.WHOISStats, error) {
+	<-ctx.Done()
+
+	return nil, ctx.Err()
+}
+
+// idleASNFetcher is a WHOIS fetcher that does nothing. The stats handlers
+// read the WHOIS stats only when the server has a fetcher.
+type idleASNFetcher struct{}
+
+func (idleASNFetcher) QueueImmediate(int) {}
+
+func (idleASNFetcher) GetStats() ASNFetcherStats {
+	return ASNFetcherStats{}
+}
+
+// TestRoutesAnswer504WhenSecondDatabaseReadIsCutOff sends a request through
+// the server's router for each route that reads the database twice, with a
+// store that answers the first read and cuts off the second when the
+// request's time limit passes. Each route answers 504 with the time limit
+// message. Without the check after the second read, the AS page answers 504
+// with an empty body and the stats routes answer 200 without the WHOIS stats.
+func TestRoutesAnswer504WhenSecondDatabaseReadIsCutOff(t *testing.T) {
+	t.Parallel()
+
+	s := New(slowSecondReadDB{}, streamer.New(logger.New(), metrics.New()),
+		logger.New(), &config.Config{})
+	s.SetASNFetcher(idleASNFetcher{})
+
+	tests := []struct {
+		path         string
+		wantJSONBody bool
+	}{
+		{path: "/as/64500"},
+		{path: "/status.json", wantJSONBody: true},
+		{path: "/api/v1/stats", wantJSONBody: true},
+	}
+
+	for _, tt := range tests {
+		checkRouteAnswers504(t, s, tt.path, tt.wantJSONBody)
+	}
+}
+
+// checkRouteAnswers504 sends a request for path through the server's router
+// with a short deadline and checks that it answers 504 with the time limit
+// message: the JSON error body on JSON routes, the plain message on pages.
+func checkRouteAnswers504(
+	t *testing.T, s *Server, path string, wantJSONBody bool,
+) {
+	t.Helper()
+
+	ctx, cancel := context.WithTimeout(context.Background(), shortRequestDeadline)
+	defer cancel()
+
+	rec := httptest.NewRecorder()
+	s.router.ServeHTTP(rec,
+		httptest.NewRequestWithContext(ctx, http.MethodGet, path, nil))
+
+	if rec.Code != http.StatusGatewayTimeout {
+		t.Errorf("%s: status %d, want %d; body %s",
+			path, rec.Code, http.StatusGatewayTimeout, rec.Body)
+	}
+
+	if wantJSONBody {
+		checkJSONErrorCode(t, path, rec, http.StatusGatewayTimeout)
+
+		return
+	}
+
+	body := strings.TrimSpace(rec.Body.String())
+	if body != requestTimeoutMessage {
+		t.Errorf("%s: body %q, want %q", path, body, requestTimeoutMessage)
+	}
+}
+
+// checkJSONErrorCode checks that rec holds the JSON error body with the given
+// code.
+func checkJSONErrorCode(
+	t *testing.T, name string, rec *httptest.ResponseRecorder, want int,
+) {
+	t.Helper()
+
+	var body struct {
+		Status string `json:"status"`
+		Error  struct {
+			Code int `json:"code"`
+		} `json:"error"`
+	}
+
+	err := json.Unmarshal(rec.Body.Bytes(), &body)
+	if err != nil {
+		t.Errorf("%s: decoding the answer %q: %v", name, rec.Body, err)
+
+		return
+	}
+
+	if body.Status != jsonStatusError || body.Error.Code != want {
+		t.Errorf("%s: answer %s, want status \"error\" and error code %d",
+			name, rec.Body, want)
+	}
+}
+
+// settledGoroutineCount lets transient goroutines finish, then reports the
+// current count.
+func settledGoroutineCount() int {
+	prev := runtime.NumGoroutine()
+
+	for range 20 {
+		time.Sleep(10 * time.Millisecond)
+
+		cur := runtime.NumGoroutine()
+		if cur == prev {
+			return cur
+		}
+
+		prev = cur
+	}
+
+	return prev
+}
+
+// waitForGoroutines waits until the goroutine count drops to target or below.
+func waitForGoroutines(target int) bool {
+	for range 100 {
+		if runtime.NumGoroutine() <= target {
+			return true
+		}
+
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	return false
+}