Add tests for AxisToButton rule. (WIP)

internal/mappingrules/test_mocks.go

@@ -0,0 +1,15 @@
+package mappingrules
+
+import (
+	"github.com/holoplot/go-evdev"
+	"github.com/stretchr/testify/mock"
+)
+
+type InputDeviceMock struct {
+	mock.Mock
+}
+
+func (m *InputDeviceMock) AbsInfos() (map[evdev.EvCode]evdev.AbsInfo, error) {
+	args := m.Called()
+	return args.Get(0).(map[evdev.EvCode]evdev.AbsInfo), args.Error(1)
+}