virtionet: testing connectUnixPath

it adds tests for connectUnixPath and localUnixSocketPath func in virtionet.go
it mainly test the use case where one end of the unixgram socket is longer of 104 bytes resulting in a failure. On macOS, a path on the filesystem can have a max of 104 bytes length

pkg/vf/virtionet_test.go

@@ -0,0 +1,100 @@
+package vf
+
+import (
+	"fmt"
+	"math/rand"
+	"net"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/crc-org/vfkit/pkg/config"
+)
+
+func testConnectUnixgram(t *testing.T) error {
+	unixSocketPath := filepath.Join("/tmp", fmt.Sprintf("vnet-test-%x.sock", rand.Int31n(0xffff))) //#nosec G404 -- no need for crypto/rand here
+	addr, err := net.ResolveUnixAddr("unixgram", unixSocketPath)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	l, err := net.ListenUnixgram("unixgram", addr)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	defer l.Close()
+	defer os.Remove(unixSocketPath)
+
+	dev := &VirtioNet{
+		&config.VirtioNet{
+			UnixSocketPath: unixSocketPath,
+		},
+		&net.UnixAddr{},
+	}
+
+	return dev.connectUnixPath()
+}
+
+func TestConnectUnixPath(t *testing.T) {
+	t.Run("Successful connection - no error", func(t *testing.T) {
+		err := testConnectUnixgram(t)
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+	})
+
+	t.Run("Failed connection - End socket longer than 104 bytes", func(t *testing.T) {
+		// Retrieve HOME env variable (used by the os.UserHomeDir)
+		origUserHome := os.Getenv("HOME")
+		defer func() {
+			os.Setenv("HOME", origUserHome)
+		}()
+
+		// Create a string of 100 bytes to update the user home to be sure to create a socket path > 104 bytes
+		b := make([]byte, 100)
+		for i := range b {
+			b[i] = 'a'
+		}
+		subDir := string(b)
+
+		// Update HOME env so os.UserHomeDir returns the update path with subfolder
+		updatedUserHome := filepath.Join(origUserHome, subDir)
+		os.Setenv("HOME", updatedUserHome)
+
+		err := testConnectUnixgram(t)
+		// It should return an error
+		if err == nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		if !strings.Contains(err.Error(), "invalid argument") {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+	})
+}
+
+func TestLocalUnixSocketPath(t *testing.T) {
+	t.Run("Success case - Creates temporary socket path", func(t *testing.T) {
+		// Retrieve HOME env variable (used by the os.UserHomeDir)
+		userHome := os.Getenv("HOME")
+
+		path, err := localUnixSocketPath()
+
+		// Assert successful execution
+		if err != nil {
+			t.Fatalf("Unexpected error: %v", err)
+		}
+
+		// Check if path starts with the expected prefix
+		expectedPrefix := filepath.Join(userHome, "Library", "Application Support", "vfkit")
+		if !strings.HasPrefix(path, expectedPrefix) {
+			t.Fatalf("Path doesn't start with expected prefix: %v", path)
+		}
+
+		// Check if path ends with a socket extension
+		if filepath.Ext(path) != ".sock" {
+			t.Fatalf("Path doesn't end with .sock extension: %v, ext is %v", path, filepath.Ext(path))
+		}
+	})
+}