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

Tests that waited a few seconds for something to happen now wait 15 seconds.
The wait ends as soon as the condition holds, so a passing run takes no longer.

TestStreamNotDroppedWhileLinesArrive, the tests whose requests pass a 2- or
4-second limit in the server, and TestStreamDurationsCountSeconds run on a fake
clock, so a stall on the host cannot change their result.

The checkpoint tests give the writing connection a 30-second busy timeout, so
their limit can be 15 seconds and a checkpoint that waits for a read still
fails them.

Model: opus-5-5

internal/server/handlers_internal_test.go

@@ -494,34 +494,37 @@ func TestStatsAnswerGivesConnectionDurationInSeconds(t *testing.T) {
 // TestStreamDurationsCountSeconds checks that the uptime and the connection
 // duration of a stream that connected 90 seconds ago are both 90. A stream
 // that has never connected has an uptime of 0, and one that is not connected
-// has no connection duration.
+// has no connection duration. The test runs in a synctest bubble, whose clock
+// is fake, so a stall on the host does not add to the 90 seconds.
 func TestStreamDurationsCountSeconds(t *testing.T) {
 	t.Parallel()
 
-	const connectedFor = 90 * time.Second
+	synctest.Test(t, func(t *testing.T) {
+		const connectedFor = 90 * time.Second
 
-	connectedSince := time.Now().Add(-connectedFor)
-	want := int64(connectedFor / time.Second)
+		connectedSince := time.Now().Add(-connectedFor)
+		want := int64(connectedFor / time.Second)
 
-	if got := uptimeSeconds(connectedSince); got != want {
-		t.Errorf("uptimeSeconds = %d, want %d", got, want)
-	}
+		if got := uptimeSeconds(connectedSince); got != want {
+			t.Errorf("uptimeSeconds = %d, want %d", got, want)
+		}
 
-	if got := uptimeSeconds(time.Time{}); got != 0 {
-		t.Errorf("uptimeSeconds before any connection = %d, want 0", got)
-	}
+		if got := uptimeSeconds(time.Time{}); got != 0 {
+			t.Errorf("uptimeSeconds before any connection = %d, want 0", got)
+		}
 
-	switch got := connectionDurationSeconds(true, connectedSince); {
-	case got == nil:
-		t.Errorf("connectionDurationSeconds = nil, want %d", want)
-	case *got != want:
-		t.Errorf("connectionDurationSeconds = %d, want %d", *got, want)
-	}
+		switch got := connectionDurationSeconds(true, connectedSince); {
+		case got == nil:
+			t.Errorf("connectionDurationSeconds = nil, want %d", want)
+		case *got != want:
+			t.Errorf("connectionDurationSeconds = %d, want %d", *got, want)
+		}
 
-	if got := connectionDurationSeconds(false, connectedSince); got != nil {
-		t.Errorf("connectionDurationSeconds while not connected = %d, want nil",
-			*got)
-	}
+		if got := connectionDurationSeconds(false, connectedSince); got != nil {
+			t.Errorf("connectionDurationSeconds while not connected = %d, want nil",
+				*got)
+		}
+	})
 }
 
 // newTestTable returns a routing table that holds a route for testPrefixV4,