Wait for the build's log lines to be stored before counting them (hq issue 507)

A line is said with a plain publish, so a live subscriber can hold both
lines while the stream has stored one or none yet; the test read the
stream once and failed under load. It now waits up to 5 s for both.

internal/link/builds_nats_test.go

@@ -123,15 +123,24 @@ func TestNatsABuildIsTakenAndItsOutcomeReachesEverybody(t *testing.T) {
 			t.Fatalf("line %d came back as %s (%v)", want, msg.Data, err)
 		}
 	}
-	// And it is in the stream for a reader who comes later.
+	// And it is in the stream for a reader who comes later. **Waited for, with a bound, rather
-	info, err := js.Context().StreamInfo(broker.EventsStream, &nats.StreamInfoRequest{SubjectsFilter: BuildLog("b-1")})
+	// than read once** (novox/hq issue 507): a line is said with a plain publish, so the server
-	if err != nil {
+	// hands it to a live subscriber and stores it in the stream independently, and under load the
-		t.Fatal(err)
+	// subscriber above had both lines while the stream still held one, or none.
+	var held map[string]uint64
+	for until := time.Now().Add(5 * time.Second); ; {
+		info, err := js.Context().StreamInfo(broker.EventsStream, &nats.StreamInfoRequest{SubjectsFilter: BuildLog("b-1")})
+		if err != nil {
+			t.Fatal(err)
+		}
+		held = info.State.Subjects
+		if held[BuildLog("b-1")] >= 2 || time.Now().After(until) {
+			break
+		}
+		time.Sleep(10 * time.Millisecond)
 	}
-	if info.State.Subjects[BuildLog("b-1")] != 2 {
+	if held[BuildLog("b-1")] != 2 {
-		t.Fatalf("the stream holds %v under the build's subject, want 2", info.State.Subjects)
+		t.Fatalf("the stream holds %v under the build's subject, want 2", held)
-	}
-	if err == nil {
 	}
 	if result.ID != "b-1" || result.Commit != "abc1234" {
 		t.Fatalf("the asker got %+v", result)