fix: Make TestAgent and TestWorkspaceAgentPTY less flaky (#1562)

coderd/workspaceagents_test.go

@@ -1,11 +1,13 @@
 package coderd_test
 
 import (
+	"bufio"
 	"context"
 	"encoding/json"
 	"runtime"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/google/uuid"
 	"github.com/pion/webrtc/v3"
@@ -230,6 +232,11 @@ func TestWorkspaceAgentPTY(t *testing.T) {
 	require.NoError(t, err)
 	_, err = conn.Write(data)
 	require.NoError(t, err)
+	bufRead := bufio.NewReader(conn)
+
+	// Brief pause to reduce the likelihood that we send keystrokes while
+	// the shell is simultaneously sending a prompt.
+	time.Sleep(100 * time.Millisecond)
 
 	data, err = json.Marshal(agent.ReconnectingPTYRequest{
 		Data: "echo test\r\n",
@@ -238,16 +245,22 @@ func TestWorkspaceAgentPTY(t *testing.T) {
 	_, err = conn.Write(data)
 	require.NoError(t, err)
 
-	findEcho := func() {
+	expectLine := func(matcher func(string) bool) {
 		for {
-			read, err := conn.Read(data)
+			line, err := bufRead.ReadString('\n')
 			require.NoError(t, err)
-			if strings.Contains(string(data[:read]), "test") {
-				return
+			if matcher(line) {
+				break
 			}
 		}
 	}
+	matchEchoCommand := func(line string) bool {
+		return strings.Contains(line, "echo test")
+	}
+	matchEchoOutput := func(line string) bool {
+		return strings.Contains(line, "test") && !strings.Contains(line, "echo")
+	}
 
-	findEcho()
-	findEcho()
+	expectLine(matchEchoCommand)
+	expectLine(matchEchoOutput)
 }