diff --git a/cli/server_test.go b/cli/server_test.go
index 64ad535ea34f3..d9019391114f3 100644
--- a/cli/server_test.go
+++ b/cli/server_test.go
@@ -25,7 +25,6 @@ import (
 	"runtime"
 	"strconv"
 	"strings"
-	"sync"
 	"sync/atomic"
 	"testing"
 	"time"
@@ -253,10 +252,8 @@ func TestServer(t *testing.T) {
 			"--access-url", "http://localhost:3000/",
 			"--cache-dir", t.TempDir(),
 		)
-		stdoutRW := syncReaderWriter{}
-		stderrRW := syncReaderWriter{}
-		inv.Stdout = io.MultiWriter(os.Stdout, &stdoutRW)
-		inv.Stderr = io.MultiWriter(os.Stderr, &stderrRW)
+		pty := ptytest.New(t).Attach(inv)
+		require.NoError(t, pty.Resize(20, 80))
 		clitest.Start(t, inv)
 
 		// Wait for startup
@@ -270,8 +267,9 @@ func TestServer(t *testing.T) {
 		// normally shown to the user, so we'll ignore them.
 		ignoreLines := []string{
 			"isn't externally reachable",
-			"install.sh will be unavailable",
+			"open install.sh: file does not exist",
 			"telemetry disabled, unable to notify of security issues",
+			"installed terraform version newer than expected",
 		}
 
 		countLines := func(fullOutput string) int {
@@ -282,9 +280,11 @@ func TestServer(t *testing.T) {
 			for _, line := range linesByNewline {
 				for _, ignoreLine := range ignoreLines {
 					if strings.Contains(line, ignoreLine) {
+						t.Logf("Ignoring: %q", line)
 						continue lineLoop
 					}
 				}
+				t.Logf("Counting: %q", line)
 				if line == "" {
 					// Empty lines take up one line.
 					countByWidth++
@@ -295,17 +295,10 @@ func TestServer(t *testing.T) {
 			return countByWidth
 		}
 
-		stdout, err := io.ReadAll(&stdoutRW)
-		if err != nil {
-			t.Fatalf("failed to read stdout: %v", err)
-		}
-		stderr, err := io.ReadAll(&stderrRW)
-		if err != nil {
-			t.Fatalf("failed to read stderr: %v", err)
-		}
-
-		numLines := countLines(string(stdout)) + countLines(string(stderr))
-		require.Less(t, numLines, 20)
+		out := pty.ReadAll()
+		numLines := countLines(string(out))
+		t.Logf("numLines: %d", numLines)
+		require.Less(t, numLines, 12, "expected less than 12 lines of output (terminal width 80), got %d", numLines)
 	})
 
 	t.Run("OAuth2GitHubDefaultProvider", func(t *testing.T) {
@@ -2355,22 +2348,3 @@ func mockTelemetryServer(t *testing.T) (*url.URL, chan *telemetry.Deployment, ch
 
 	return serverURL, deployment, snapshot
 }
-
-// syncWriter provides a thread-safe io.ReadWriter implementation
-type syncReaderWriter struct {
-	buf bytes.Buffer
-	mu  sync.Mutex
-}
-
-func (w *syncReaderWriter) Write(p []byte) (n int, err error) {
-	w.mu.Lock()
-	defer w.mu.Unlock()
-	return w.buf.Write(p)
-}
-
-func (w *syncReaderWriter) Read(p []byte) (n int, err error) {
-	w.mu.Lock()
-	defer w.mu.Unlock()
-
-	return w.buf.Read(p)
-}
diff --git a/pty/ptytest/ptytest.go b/pty/ptytest/ptytest.go
index 3c86970ec0006..42d9f34a7bae0 100644
--- a/pty/ptytest/ptytest.go
+++ b/pty/ptytest/ptytest.go
@@ -319,6 +319,11 @@ func (e *outExpecter) ReadLine(ctx context.Context) string {
 	return buffer.String()
 }
 
+func (e *outExpecter) ReadAll() []byte {
+	e.t.Helper()
+	return e.out.ReadAll()
+}
+
 func (e *outExpecter) doMatchWithDeadline(ctx context.Context, name string, fn func(*bufio.Reader) error) error {
 	e.t.Helper()
 
@@ -460,6 +465,18 @@ func newStdbuf() *stdbuf {
 	return &stdbuf{more: make(chan struct{}, 1)}
 }
 
+func (b *stdbuf) ReadAll() []byte {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	if b.err != nil {
+		return nil
+	}
+	p := append([]byte(nil), b.b...)
+	b.b = b.b[len(b.b):]
+	return p
+}
+
 func (b *stdbuf) Read(p []byte) (int, error) {
 	if b.r == nil {
 		return b.readOrWaitForMore(p)