Support PluginWatcher in Windows

Signed-off-by: Deep Debroy <ddebroy@docker.com>

pkg/kubelet/util/util_unix_test.go

@@ -19,9 +19,13 @@ limitations under the License.
 package util
 
 import (
+	"io/ioutil"
+	"net"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestParseEndpoint(t *testing.T) {
@@ -69,3 +73,63 @@ func TestParseEndpoint(t *testing.T) {
 	}
 
 }
+
+func TestIsUnixDomainSocket(t *testing.T) {
+	tests := []struct {
+		label          string
+		listenOnSocket bool
+		expectSocket   bool
+		expectError    bool
+		invalidFile    bool
+	}{
+		{
+			label:          "Domain Socket file",
+			listenOnSocket: true,
+			expectSocket:   true,
+			expectError:    false,
+		},
+		{
+			label:       "Non Existent file",
+			invalidFile: true,
+			expectError: true,
+		},
+		{
+			label:          "Regular file",
+			listenOnSocket: false,
+			expectSocket:   false,
+			expectError:    false,
+		},
+	}
+	for _, test := range tests {
+		f, err := ioutil.TempFile("", "test-domain-socket")
+		require.NoErrorf(t, err, "Failed to create file for test purposes: %v while setting up: %s", err, test.label)
+		addr := f.Name()
+		f.Close()
+		var ln *net.UnixListener
+		if test.listenOnSocket {
+			os.Remove(addr)
+			ta, err := net.ResolveUnixAddr("unix", addr)
+			require.NoErrorf(t, err, "Failed to ResolveUnixAddr: %v while setting up: %s", err, test.label)
+			ln, err = net.ListenUnix("unix", ta)
+			require.NoErrorf(t, err, "Failed to ListenUnix: %v while setting up: %s", err, test.label)
+		}
+		fileToTest := addr
+		if test.invalidFile {
+			fileToTest = fileToTest + ".invalid"
+		}
+		result, err := IsUnixDomainSocket(fileToTest)
+		if test.listenOnSocket {
+			// this takes care of removing the file associated with the domain socket
+			ln.Close()
+		} else {
+			// explicitly remove regular file
+			os.Remove(addr)
+		}
+		if test.expectError {
+			assert.NotNil(t, err, "Unexpected nil error from IsUnixDomainSocket for %s", test.label)
+		} else {
+			assert.Nil(t, err, "Unexpected error invoking IsUnixDomainSocket for %s", test.label)
+		}
+		assert.Equal(t, result, test.expectSocket, "Unexpected result from IsUnixDomainSocket: %v for %s", result, test.label)
+	}
+}