Make the tests pass on a busy host (closes #240)

Tests that wait on the real clock failed when the host stalled for a few seconds, although the code was right. Waits for something that should happen are now mostly 15 seconds. Tests whose result depends on a short idle timeout or a production request limit run under `synctest.Test`, on a fake clock, with a fake transport where a real connection would stop that clock. Test code only.

Judgement call: the 5-second waits in three `internal/streamer` tests also became 15 seconds.

Model: opus-5-5

internal/server/middleware_internal_test.go

@@ -14,6 +14,7 @@ import (
 	"regexp"
 	"strings"
 	"testing"
+	"testing/synctest"
 	"time"
 
 	"git.eeqj.de/sneak/routewatch/internal/config"
@@ -163,6 +164,10 @@ func TestJSONAnswersPutNoUnitInAString(t *testing.T) {
 // router and the middleware write. Before the fix a panic in a handler, and a
 // method /status.json or the health check does not take, answered with an
 // empty body (https://git.eeqj.de/sneak/routewatch/issues/201).
+//
+// The requests run in a synctest bubble, whose clock is fake, so a stall on
+// the host does not use up the 2-second limit of the health check or the
+// 4-second limit of the stats handlers.
 func TestJSONAnswersCarryMeta(t *testing.T) {
 	t.Parallel()
 
@@ -181,6 +186,10 @@ func TestJSONAnswersCarryMeta(t *testing.T) {
 	s.router.Get(panicsPath, JSONValidationMiddleware(http.HandlerFunc(
 		func(http.ResponseWriter, *http.Request) { panic(errDiskIO) })).ServeHTTP)
 
+	failing := New(failingDB{}, newTestTable(),
+		streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
+	failing.resolver = &fakeResolver{}
+
 	tests := []struct {
 		method   string
 		path     string
@@ -216,42 +225,40 @@ func TestJSONAnswersCarryMeta(t *testing.T) {
 		{http.MethodGet, panicsPath, http.StatusInternalServerError},
 	}
 
-	for _, tt := range tests {
-		checkAnswerCarriesMeta(t, s, httptest.NewRequestWithContext(
-			t.Context(), tt.method, tt.path, nil), tt.wantCode)
-	}
+	synctest.Test(t, func(t *testing.T) {
+		for _, tt := range tests {
+			checkAnswerCarriesMeta(t, s, httptest.NewRequestWithContext(
+				t.Context(), tt.method, tt.path, nil), tt.wantCode)
+		}
 
-	// A request whose time limit has already passed answers 504. The handlers
-	// write the answers of the first five routes, and the JSON check on the
-	// route writes the last.
-	pastTimeLimit, cancel := context.WithDeadline(t.Context(), time.Now())
-	defer cancel()
+		// A request whose time limit has already passed answers 504. The
+		// handlers write the answers of the first five routes, and the JSON
+		// check on the route writes the last.
+		pastTimeLimit, cancel := context.WithDeadline(t.Context(), time.Now())
+		defer cancel()
 
-	for _, path := range []string{
-		statusJSONPath, statsPath, "/ip/" + addrInTestPrefixV4,
-		"/api/v1/ip/" + addrInTestPrefixV4, asJSONPath, writesNothingPath,
-	} {
-		checkAnswerCarriesMeta(t, s, httptest.NewRequestWithContext(
-			pastTimeLimit, http.MethodGet, path, nil), http.StatusGatewayTimeout)
-	}
+		for _, path := range []string{
+			statusJSONPath, statsPath, "/ip/" + addrInTestPrefixV4,
+			"/api/v1/ip/" + addrInTestPrefixV4, asJSONPath, writesNothingPath,
+		} {
+			checkAnswerCarriesMeta(t, s, httptest.NewRequestWithContext(
+				pastTimeLimit, http.MethodGet, path, nil), http.StatusGatewayTimeout)
+		}
 
-	// With a store whose reads fail, the health check answers 503, and the
-	// handlers of the other routes 500.
-	failing := New(failingDB{}, newTestTable(),
-		streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
-	failing.resolver = &fakeResolver{}
-
-	checkAnswerCarriesMeta(t, failing, httptest.NewRequestWithContext(
-		t.Context(), http.MethodGet, healthCheckPath, nil),
-		http.StatusServiceUnavailable)
-
-	for _, path := range []string{
-		statusJSONPath, statsPath, asJSONPath,
-		"/api/v1/ip/" + addrInTestPrefixV4, "/ip/" + addrInTestPrefixV4,
-	} {
+		// With a store whose reads fail, the health check answers 503, and
+		// the handlers of the other routes 500.
 		checkAnswerCarriesMeta(t, failing, httptest.NewRequestWithContext(
-			t.Context(), http.MethodGet, path, nil), http.StatusInternalServerError)
-	}
+			t.Context(), http.MethodGet, healthCheckPath, nil),
+			http.StatusServiceUnavailable)
+
+		for _, path := range []string{
+			statusJSONPath, statsPath, asJSONPath,
+			"/api/v1/ip/" + addrInTestPrefixV4, "/ip/" + addrInTestPrefixV4,
+		} {
+			checkAnswerCarriesMeta(t, failing, httptest.NewRequestWithContext(
+				t.Context(), http.MethodGet, path, nil), http.StatusInternalServerError)
+		}
+	})
 }
 
 // checkAnswerCarriesMeta serves req through the server's router, and checks