mountlib: fix cross platform tests

cmd/mountlib/mounttest/write_unix.go

@@ -0,0 +1,50 @@
+// +build linux darwin freebsd
+
+package mounttest
+
+import (
+	"os"
+	"syscall"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// TestWriteFileDoubleClose tests double close on write
+func TestWriteFileDoubleClose(t *testing.T) {
+	run.skipIfNoFUSE(t)
+
+	out, err := os.Create(run.path("testdoubleclose"))
+	assert.NoError(t, err)
+	fd := out.Fd()
+
+	fd1, err := syscall.Dup(int(fd))
+	assert.NoError(t, err)
+
+	fd2, err := syscall.Dup(int(fd))
+	assert.NoError(t, err)
+
+	// close one of the dups - should produce no error
+	err = syscall.Close(fd1)
+	assert.NoError(t, err)
+
+	// write to the file
+	buf := []byte("hello")
+	n, err := out.Write(buf)
+	assert.NoError(t, err)
+	assert.Equal(t, 5, n)
+
+	// close it
+	err = out.Close()
+	assert.NoError(t, err)
+
+	// write to the other dup - should produce an error
+	n, err = syscall.Write(fd2, buf)
+	assert.Error(t, err, "input/output error")
+
+	// close the dup - should produce an error
+	err = syscall.Close(fd2)
+	assert.Error(t, err, "input/output error")
+
+	run.rm(t, "testdoubleclose")
+}