test: don't use ptytest for client side of SSH session tests (#27681)

In our initial batches of test refactors, I left the SSH session tests using `ptytest` because I (erroneously) thought that we still needed a client side PTY when the SSH server creates a PTY. This is incorrect and plain in-process IO is fine on the client side.  
  
closes https://github.com/coder/internal/issues/1400   
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agent/agent_test.go

@@ -54,10 +54,10 @@ import (
 	"github.com/coder/coder/v2/codersdk/agentsdk"
 	"github.com/coder/coder/v2/codersdk/workspacesdk"
 	"github.com/coder/coder/v2/cryptorand"
-	"github.com/coder/coder/v2/pty/ptytest"
 	"github.com/coder/coder/v2/tailnet"
 	"github.com/coder/coder/v2/tailnet/tailnettest"
 	"github.com/coder/coder/v2/testutil"
+	"github.com/coder/coder/v2/testutil/expecter"
 	"github.com/coder/quartz"
 )
 
@@ -721,6 +721,7 @@ func TestAgent_SessionTTYShell(t *testing.T) {
 		t.Run(fmt.Sprintf("(%d)", port), func(t *testing.T) {
 			t.Parallel()
 			ctx := testutil.Context(t, testutil.WaitMedium)
+			logger := testutil.Logger(t)
 
 			session := setupSSHSessionOnPort(t, agentsdk.Manifest{}, codersdk.ServiceBannerConfig{}, nil, port)
 			command := "sh"
@@ -729,16 +730,14 @@ func TestAgent_SessionTTYShell(t *testing.T) {
 			}
 			err := session.RequestPty("xterm", 128, 128, ssh.TerminalModes{})
 			require.NoError(t, err)
-			ptty := ptytest.New(t)
-			session.Stdout = ptty.Output()
-			session.Stderr = ptty.Output()
-			session.Stdin = ptty.Input()
+			stdout := expecter.NewAttachedToSSHSession(t, session)
+			stdin := testutil.NewWriterAttachedToSSHSession(t, logger.Named("sshin"), session)
 			err = session.Start(command)
 			require.NoError(t, err)
-			_ = ptty.Peek(ctx, 1) // wait for the prompt
-			ptty.WriteLine("echo test")
-			ptty.ExpectMatch(ctx, "test")
-			ptty.WriteLine("exit")
+			_ = stdout.Peek(ctx, 1) // wait for the prompt
+			stdin.WriteLine("echo test")
+			stdout.ExpectMatch(ctx, "test")
+			stdin.WriteLine("exit")
 			err = session.Wait()
 			require.NoError(t, err)
 		})
@@ -751,10 +750,6 @@ func TestAgent_SessionTTYExitCode(t *testing.T) {
 	command := "areallynotrealcommand"
 	err := session.RequestPty("xterm", 128, 128, ssh.TerminalModes{})
 	require.NoError(t, err)
-	ptty := ptytest.New(t)
-	session.Stdout = ptty.Output()
-	session.Stderr = ptty.Output()
-	session.Stdin = ptty.Input()
 	err = session.Start(command)
 	require.NoError(t, err)
 	err = session.Wait()
@@ -1035,9 +1030,8 @@ func TestAgent_Session_TTY_QuietLogin(t *testing.T) {
 		require.NoError(t, err)
 
 		stdout := testutil.NewWaitBuffer()
-		ptty := ptytest.New(t)
+
 		session.Stdout = stdout
-		session.Stderr = ptty.Output()
 		stdin, err := session.StdinPipe()
 		require.NoError(t, err)
 		require.NoError(t, session.Shell())
@@ -1076,8 +1070,6 @@ func TestAgent_Session_TTY_FastCommandHasOutput(t *testing.T) {
 	require.NoError(t, err)
 	defer sshClient.Close()
 
-	ptty := ptytest.New(t)
-
 	var stdout bytes.Buffer
 	// NOTE(mafredri): Increase iterations to increase chance of failure,
 	//                 assuming bug is present. Limiting GOMAXPROCS further
@@ -1097,8 +1089,6 @@ func TestAgent_Session_TTY_FastCommandHasOutput(t *testing.T) {
 			require.NoError(t, err)
 
 			session.Stdout = &stdout
-			session.Stderr = ptty.Output()
-			session.Stdin = ptty.Input()
 			err = session.Start("echo wazzup")
 			require.NoError(t, err)
 
@@ -1126,8 +1116,6 @@ func TestAgent_Session_TTY_HugeOutputIsNotLost(t *testing.T) {
 	require.NoError(t, err)
 	defer sshClient.Close()
 
-	ptty := ptytest.New(t)
-
 	var stdout bytes.Buffer
 	// NOTE(mafredri): Increase iterations to increase chance of failure,
 	//                 assuming bug is present.
@@ -1146,8 +1134,6 @@ func TestAgent_Session_TTY_HugeOutputIsNotLost(t *testing.T) {
 			require.NoError(t, err)
 
 			session.Stdout = &stdout
-			session.Stderr = ptty.Output()
-			session.Stdin = ptty.Input()
 			want := strings.Repeat("wazzup", 1024+1) // ~6KB, +1 because 1024 is a common buffer size.
 			err = session.Start("echo " + want)
 			require.NoError(t, err)
@@ -4220,19 +4206,18 @@ func assertWritePayload(t testing.TB, w io.Writer, payload []byte) {
 
 func testSessionOutput(t *testing.T, session *ssh.Session, expected, unexpected []string, expectedRe *regexp.Regexp) {
 	t.Helper()
+	logger := testutil.Logger(t)
 
 	err := session.RequestPty("xterm", 128, 128, ssh.TerminalModes{})
 	require.NoError(t, err)
 
-	ptty := ptytest.New(t)
 	var stdout bytes.Buffer
 	session.Stdout = &stdout
-	session.Stderr = ptty.Output()
-	session.Stdin = ptty.Input()
+	stdin := testutil.NewWriterAttachedToSSHSession(t, logger.Named("sshin"), session)
 	err = session.Shell()
 	require.NoError(t, err)
 
-	ptty.WriteLine("exit 0")
+	stdin.WriteLine("exit 0")
 
 	waitErr := make(chan error, 1)
 	go func() {

agent/agentssh/agentssh_test.go

@@ -28,8 +28,8 @@ import (
 	"cdr.dev/slog/v3/sloggers/slogtest"
 	"github.com/coder/coder/v2/agent/agentexec"
 	"github.com/coder/coder/v2/agent/agentssh"
-	"github.com/coder/coder/v2/pty/ptytest"
 	"github.com/coder/coder/v2/testutil"
+	"github.com/coder/coder/v2/testutil/expecter"
 )
 
 func TestMain(m *testing.M) {
@@ -182,10 +182,8 @@ func TestNewServer_CloseActiveConnections(t *testing.T) {
 				c := sshClient(t, ln.Addr().String())
 				sess, err := c.NewSession()
 				assert.NoError(t, err)
-				pty := ptytest.New(t)
-				sess.Stdin = pty.Input()
-				sess.Stdout = pty.Output()
-				sess.Stderr = pty.Output()
+				stdout := expecter.NewAttachedToSSHSession(t, sess)
+				stdout.Rename(fmt.Sprintf("sess%d", i))
 
 				// Every other session will request a PTY.
 				if i%2 == 0 {
@@ -203,7 +201,7 @@ func TestNewServer_CloseActiveConnections(t *testing.T) {
 				assert.NoError(t, err)
 
 				// Allow the session to settle (i.e. reach echo).
-				pty.ExpectMatch(ctx, "started")
+				stdout.ExpectMatch(ctx, "started")
 				// Sleep a bit to ensure the sleep has started.
 				time.Sleep(testutil.IntervalMedium)
 
@@ -353,18 +351,11 @@ func TestNewServer_Signal(t *testing.T) {
 
 		c := sshClient(t, ln.Addr().String())
 
-		pty := ptytest.New(t)
-
 		sess, err := c.NewSession()
 		require.NoError(t, err)
 		r, err := sess.StdoutPipe()
 		require.NoError(t, err)
 
-		// Note, we request pty but don't use ptytest here because we can't
-		// easily test for no text before EOF.
-		sess.Stdin = pty.Input()
-		sess.Stderr = pty.Output()
-
 		err = sess.RequestPty("xterm", 80, 80, nil)
 		require.NoError(t, err)