add monitor test

Author: lucarin91

internal/monitor/monitor.go

@@ -21,13 +21,22 @@ import (
 	"log/slog"
 	"net"
 	"time"
+
+	"go.bug.st/f"
 )
 
-const monitorAddr = "127.0.0.1:7500"
+const defaultArduinoRouterMonitorAddress = "127.0.0.1:7500"
+
+func NewMonitorHandler(rw io.ReadWriteCloser, address ...string) (func(), error) {
+	f.Assert(len(address) <= 1, "NewMonitorHandler accepts at most one address argument")
+
+	addr := defaultArduinoRouterMonitorAddress
+	if len(address) == 1 {
+		addr = address[0]
+	}
 
-func NewMonitorHandler(rw io.ReadWriteCloser) (func(), error) {
 	// Connect to monitor
-	monitor, err := net.DialTimeout("tcp", monitorAddr, time.Second)
+	monitor, err := net.DialTimeout("tcp", addr, time.Second)
 	if err != nil {
 		return nil, err
 	}

internal/monitor/monitor_test.go

@@ -0,0 +1,69 @@
+package monitor
+
+import (
+	"fmt"
+	"io"
+	"net"
+	"testing"
+
+	"github.com/arduino/arduino-app-cli/pkg/x/ports"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonitorHandler(t *testing.T) {
+	addr := startEcoMonitor(t)
+
+	t.Logf("Started echo monitor at %s", addr.String())
+
+	// Use pipes to simulate ReadWriteCloser
+	rOut, wIn := io.Pipe()
+	rIn, wOut := io.Pipe()
+	type pipeReadWriteCloser struct {
+		io.Reader
+		io.Writer
+		io.Closer
+	}
+	pr := &pipeReadWriteCloser{
+		Reader: rOut,
+		Writer: wOut,
+		Closer: io.NopCloser(nil),
+	}
+
+	handler, err := NewMonitorHandler(pr, addr.String())
+	assert.NoError(t, err)
+	go handler()
+
+	// Write data to the pipe writer
+	message := "Hello, Monitor!"
+	n, err := wIn.Write([]byte(message))
+	assert.NoError(t, err)
+	assert.Equal(t, len(message), n)
+
+	// Read data from the pipe reader
+	buf := [128]byte{}
+	n, err = rIn.Read(buf[:])
+	assert.NoError(t, err)
+	assert.Equal(t, len(message), n)
+	assert.Equal(t, message, string(buf[:n]))
+}
+
+func startEcoMonitor(t *testing.T) net.Addr {
+	t.Helper()
+
+	port, err := ports.GetAvailable()
+	assert.NoError(t, err)
+
+	ln, err := net.Listen("tcp", fmt.Sprintf("localhost:%d", port))
+	assert.NoError(t, err)
+	t.Cleanup(func() { _ = ln.Close() })
+
+	go func() {
+		for {
+			conn, err := ln.Accept()
+			assert.NoError(t, err)
+			go io.Copy(conn, conn) // Echo server
+		}
+	}()
+
+	return ln.Addr()
+}