test: Address a race in test with initializatoin order changes.

Per the comment in `pipestream_unix_test.go` the write end needs to exist to
stop the read end thinking it's EOF already.

Do we need to introduce liveness hacks to decide if EOF is meaningful?

internal/tailer/logstream/pipestream_unix_test.go

@@ -20,6 +20,14 @@ import (
 	"golang.org/x/sys/unix"
 )
 
+// In pipestream tests we must create the write end of the pipe before opening
+// the logstream.  If the logstream is created first, then there is an
+// opportuity for a race if the Read gets scheduled before the write end has
+// opened, because then https://github.com/golang/go/issues/44176 occurs -- the
+// call returns EOF signalling the end of input.  This might actually be
+// desirable behaviour because `pipe(7)` says that if all writers are closed, a
+// read returns EOF.
+
 func TestPipeStreamReadCompletedBecauseClosed(t *testing.T) {
 	testutil.TimeoutTest(1*time.Second, func(t *testing.T) { //nolint:thelper
 		var wg sync.WaitGroup
@@ -32,10 +40,6 @@ func TestPipeStreamReadCompletedBecauseClosed(t *testing.T) {
 		ctx, cancel := context.WithCancel(context.Background())
 		waker := waker.NewTestAlways()
 
-		// In this and the following test, open RDWR so as to not block this thread
-		// from proceeding.  If we open the logstream first, there is a race before
-		// the write end opens that can sometimes lead to the logstream reading an
-		// EOF (because the write end is not yet open) and the test fails.
 		f, err := os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
 		testutil.FatalIfErr(t, err)
 
@@ -49,6 +53,9 @@ func TestPipeStreamReadCompletedBecauseClosed(t *testing.T) {
 
 		testutil.WriteString(t, f, "1\n")
 
+		// Park this thread and hope the logstream gets a chance to read it.
+		time.Sleep(10 * time.Millisecond)
+
 		// Pipes need to be closed to signal to the pipeStream to finish up.
 		testutil.FatalIfErr(t, f.Close())
 
@@ -111,6 +118,9 @@ func TestPipeStreamReadURL(t *testing.T) {
 	defer cancel()
 	waker := waker.NewTestAlways()
 
+	f, err := os.OpenFile(name, os.O_RDWR, os.ModeNamedPipe)
+	testutil.FatalIfErr(t, err)
+
 	ps, err := logstream.New(ctx, &wg, waker, "file://"+name, logstream.OneShotDisabled)
 	testutil.FatalIfErr(t, err)
 
@@ -120,15 +130,13 @@ func TestPipeStreamReadURL(t *testing.T) {
 	}
 	checkLineDiff := testutil.ExpectLinesReceivedNoDiff(t, expected, ps.Lines())
 
-	f, err := os.OpenFile(name, os.O_WRONLY, os.ModeNamedPipe)
-	testutil.FatalIfErr(t, err)
 	testutil.WriteString(t, f, "1\n")
 
+	testutil.WriteString(t, f, "2\n")
+
 	// Give the stream a chance to wake and read
 	time.Sleep(10 * time.Millisecond)
 
-	testutil.WriteString(t, f, "2\n")
-
 	// Pipes need to be closed to signal to the pipeStream to finish up.
 	testutil.FatalIfErr(t, f.Close())