diff --git a/helper/args_test.go b/helper/args_test.go
new file mode 100644
index 0000000..378c6dc
--- /dev/null
+++ b/helper/args_test.go
@@ -0,0 +1,29 @@
+package helper_test
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+
+	"git.ophivana.moe/cat/fortify/helper"
+)
+
+func Test_argsFD_String(t *testing.T) {
+	argsOnce.Do(prepareArgs)
+
+	wantString := strings.Join(want, " ")
+	if got := argsWt.(fmt.Stringer).String(); got != wantString {
+		t.Errorf("String(): got %v; want %v",
+			got, wantString)
+	}
+}
+
+func TestNewCheckedArgs(t *testing.T) {
+	args := []string{"\x00"}
+	if _, err := helper.NewCheckedArgs(args); !errors.Is(err, helper.ErrContainsNull) {
+		t.Errorf("NewCheckedArgs(%q) error = %v, wantErr %v",
+			args,
+			err, helper.ErrContainsNull)
+	}
+}
diff --git a/helper/helper_test.go b/helper/helper_test.go
new file mode 100644
index 0000000..6b27e68
--- /dev/null
+++ b/helper/helper_test.go
@@ -0,0 +1,182 @@
+package helper_test
+
+import (
+	"io"
+	"strings"
+	"sync"
+	"testing"
+
+	"git.ophivana.moe/cat/fortify/helper"
+)
+
+var (
+	want = []string{
+		"unix:path=/run/dbus/system_bus_socket",
+		"/tmp/fortify.1971/12622d846cc3fe7b4c10359d01f0eb47/system_bus_socket",
+		"--filter",
+		"--talk=org.bluez",
+		"--talk=org.freedesktop.Avahi",
+		"--talk=org.freedesktop.UPower",
+	}
+
+	wantPayload string
+	argsWt      io.WriterTo
+	argsOnce    sync.Once
+)
+
+func prepareArgs() {
+	wantPayload = strings.Join(want, "\x00") + "\x00"
+
+	if a, err := helper.NewCheckedArgs(want); err != nil {
+		panic(err.Error())
+	} else {
+		argsWt = a
+	}
+}
+
+func TestHelper_StartNotify_Close_Wait(t *testing.T) {
+	helper.ReplaceExecCommand(t)
+	argsOnce.Do(prepareArgs)
+
+	t.Run("start helper with status channel", func(t *testing.T) {
+		h := helper.New(argsWt, "crash-test-dummy", "--args=3", "--fd=4")
+		ready := make(chan error, 1)
+
+		stdout, stderr := new(strings.Builder), new(strings.Builder)
+		h.Stdout, h.Stderr = stdout, stderr
+
+		t.Run("wait not yet started helper", func(t *testing.T) {
+			wantErr := "exec: not started"
+			if err := h.Wait(); err != nil && err.Error() != wantErr {
+				t.Errorf("Wait(%v) error = %v, wantErr %v",
+					ready,
+					err, wantErr)
+				return
+			}
+		})
+
+		if err := h.StartNotify(ready); err != nil {
+			t.Errorf("StartNotify(%v) error = %v",
+				ready,
+				err)
+			return
+		}
+
+		t.Run("start already started helper", func(t *testing.T) {
+			wantErr := "exec: already started"
+			if err := h.StartNotify(ready); err != nil && err.Error() != wantErr {
+				t.Errorf("StartNotify(%v) error = %v, wantErr %v",
+					ready,
+					err, wantErr)
+				return
+			}
+		})
+
+		if err := <-ready; err != nil {
+			t.Errorf("StartNotify(%v) latent error = %v",
+				ready,
+				err)
+		}
+
+		if err := h.Close(); err != nil {
+			t.Errorf("Close() error = %v",
+				err)
+		}
+
+		if err := h.Wait(); err != nil {
+			t.Errorf("Wait() err = %v stderr = %s",
+				err, stderr)
+		}
+
+		t.Run("wait already finalised helper", func(t *testing.T) {
+			wantErr := "exec: Wait was already called"
+			if err := h.Wait(); err != nil && err.Error() != wantErr {
+				t.Errorf("Wait(%v) error = %v, wantErr %v",
+					ready,
+					err, wantErr)
+				return
+			}
+		})
+
+		if got := stdout.String(); !strings.HasPrefix(got, wantPayload) {
+			t.Errorf("StartNotify(%v) stdout = %v, want %v",
+				ready,
+				got, wantPayload)
+		}
+	})
+}
+func TestHelper_Start_Close_Wait(t *testing.T) {
+	helper.ReplaceExecCommand(t)
+	argsOnce.Do(prepareArgs)
+
+	var wt io.WriterTo
+	if a, err := helper.NewCheckedArgs(want); err != nil {
+		t.Errorf("NewCheckedArgs(%q) error = %v",
+			want,
+			err)
+		return
+	} else {
+		wt = a
+	}
+
+	t.Run("start helper", func(t *testing.T) {
+		h := helper.New(wt, "crash-test-dummy", "--args=3")
+
+		stdout, stderr := new(strings.Builder), new(strings.Builder)
+		h.Stdout, h.Stderr = stdout, stderr
+
+		if err := h.Start(); err != nil {
+			t.Errorf("Start() error = %v",
+				err)
+			return
+		}
+
+		t.Run("close helper without status pipe", func(t *testing.T) {
+			defer func() {
+				wantPanic := "attempted to close helper with no status pipe"
+				if r := recover(); r != wantPanic {
+					t.Errorf("Close() panic = %v, wantPanic %v",
+						r, wantPanic)
+				}
+			}()
+			if err := h.Close(); err != nil {
+				t.Errorf("Close() error = %v",
+					err)
+				return
+			}
+		})
+
+		if err := h.Wait(); err != nil {
+			t.Errorf("Wait() err = %v stderr = %s",
+				err, stderr)
+		}
+
+		if got := stdout.String(); !strings.HasPrefix(got, wantPayload) {
+			t.Errorf("Start() stdout = %v, want %v",
+				got, wantPayload)
+		}
+	})
+}
+
+func TestNew(t *testing.T) {
+	t.Run("valid new helper nil check", func(t *testing.T) {
+		swt, _ := helper.NewCheckedArgs(make([]string, 1))
+		if got := helper.New(swt, "fortify"); got == nil {
+			t.Errorf("New(%q, %q) got nil",
+				swt, "fortify")
+			return
+		}
+	})
+
+	t.Run("invalid new helper panic", func(t *testing.T) {
+		defer func() {
+			want := "attempted to create helper with invalid argument writer"
+			if r := recover(); r != want {
+				t.Errorf("New: panic = %q, want %q",
+					r, want)
+			}
+		}()
+
+		helper.New(nil, "fortify")
+	})
+}