diff --git a/container/params.go b/container/params.go
index a5b4f2f..09be370 100644
--- a/container/params.go
+++ b/container/params.go
@@ -9,7 +9,8 @@ import (
 )
 
 var (
-	ErrNotSet = errors.New("environment variable not set")
+	ErrNotSet   = errors.New("environment variable not set")
+	ErrFdFormat = errors.New("bad file descriptor representation")
 )
 
 // Setup appends the read end of a pipe for setup params transmission and returns its fd.
@@ -31,7 +32,7 @@ func Receive(key string, e any, v **os.File) (func() error, error) {
 		return nil, ErrNotSet
 	} else {
 		if fd, err := strconv.Atoi(s); err != nil {
-			return nil, err
+			return nil, ErrFdFormat
 		} else {
 			setup = os.NewFile(uintptr(fd), "setup")
 			if setup == nil {
diff --git a/container/params_test.go b/container/params_test.go
new file mode 100644
index 0000000..537d686
--- /dev/null
+++ b/container/params_test.go
@@ -0,0 +1,123 @@
+package container_test
+
+import (
+	"errors"
+	"os"
+	"slices"
+	"strconv"
+	"syscall"
+	"testing"
+
+	"hakurei.app/container"
+)
+
+func TestSetupReceive(t *testing.T) {
+	t.Run("not set", func(t *testing.T) {
+		const key = "TEST_ENV_NOT_SET"
+		{
+			v, ok := os.LookupEnv(key)
+			t.Cleanup(func() {
+				if ok {
+					if err := os.Setenv(key, v); err != nil {
+						t.Fatalf("Setenv: error = %v", err)
+					}
+				} else {
+					if err := os.Unsetenv(key); err != nil {
+						t.Fatalf("Unsetenv: error = %v", err)
+					}
+				}
+			})
+		}
+
+		if _, err := container.Receive(key, nil, nil); !errors.Is(err, container.ErrNotSet) {
+			t.Errorf("Receive: error = %v, want %v", err, container.ErrNotSet)
+		}
+	})
+
+	t.Run("format", func(t *testing.T) {
+		const key = "TEST_ENV_FORMAT"
+		t.Setenv(key, "")
+
+		if _, err := container.Receive(key, nil, nil); !errors.Is(err, container.ErrFdFormat) {
+			t.Errorf("Receive: error = %v, want %v", err, container.ErrFdFormat)
+		}
+	})
+
+	t.Run("range", func(t *testing.T) {
+		const key = "TEST_ENV_RANGE"
+		t.Setenv(key, "-1")
+
+		if _, err := container.Receive(key, nil, nil); !errors.Is(err, syscall.EBADF) {
+			t.Errorf("Receive: error = %v, want %v", err, syscall.EBADF)
+		}
+	})
+
+	t.Run("setup receive", func(t *testing.T) {
+		check := func(t *testing.T, useNilFp bool) {
+			const key = "TEST_SETUP_RECEIVE"
+			payload := []int{syscall.MS_MGC_VAL, syscall.MS_MGC_MSK, syscall.MS_ASYNC, syscall.MS_ACTIVE}
+
+			encoderDone := make(chan error, 1)
+			extraFiles := make([]*os.File, 0, 1)
+			if fd, encoder, err := container.Setup(&extraFiles); err != nil {
+				t.Fatalf("Setup: error = %v", err)
+			} else if fd != 3 {
+				t.Fatalf("Setup: fd = %d, want 3", fd)
+			} else {
+				go func() { encoderDone <- encoder.Encode(payload) }()
+			}
+
+			if len(extraFiles) != 1 {
+				t.Fatalf("extraFiles: len = %v, want 1", len(extraFiles))
+			}
+
+			var dupFd int
+			if fd, err := syscall.Dup(int(extraFiles[0].Fd())); err != nil {
+				t.Fatalf("Dup: error = %v", err)
+			} else {
+				syscall.CloseOnExec(fd)
+				dupFd = fd
+				t.Setenv(key, strconv.Itoa(fd))
+			}
+
+			var (
+				gotPayload []int
+				fp         **os.File
+			)
+			if !useNilFp {
+				fp = new(*os.File)
+			}
+			var closeFile func() error
+			if f, err := container.Receive(key, &gotPayload, fp); err != nil {
+				t.Fatalf("Receive: error = %v", err)
+			} else {
+				closeFile = f
+
+				if !slices.Equal(payload, gotPayload) {
+					t.Errorf("Receive: %#v, want %#v", gotPayload, payload)
+				}
+			}
+			if !useNilFp {
+				if name := (*fp).Name(); name != "setup" {
+					t.Errorf("Name: %s, want setup", name)
+				}
+				if fd := int((*fp).Fd()); fd != dupFd {
+					t.Errorf("Fd: %d, want %d", fd, dupFd)
+				}
+			}
+
+			if err := <-encoderDone; err != nil {
+				t.Errorf("Encode: error = %v", err)
+			}
+
+			if closeFile != nil {
+				if err := closeFile(); err != nil {
+					t.Errorf("Close: error = %v", err)
+				}
+			}
+		}
+
+		t.Run("fp", func(t *testing.T) { check(t, false) })
+		t.Run("nil", func(t *testing.T) { check(t, true) })
+	})
+}