diff --git a/gpio.go b/gpio.go
index 4f4a091..de83fb0 100644
--- a/gpio.go
+++ b/gpio.go
@@ -151,6 +151,7 @@ type GPIODriver interface {
 var gpioDriverInitialized bool
 var gpioDriverInstance GPIODriver
 
+// SetGpioDriver should be used only for testing purpose.It makes possible to unit test embd gpio functionality
 func SetGpioDriver(drv GPIODriver, initialized bool) {
 	gpioDriverInstance = drv
 	gpioDriverInitialized = initialized
diff --git a/i2c.go b/i2c.go
index 414cd86..d09fcbf 100644
--- a/i2c.go
+++ b/i2c.go
@@ -43,6 +43,7 @@ type I2CDriver interface {
 var i2cDriverInitialized bool
 var i2cDriverInstance I2CDriver
 
+// SetI2cDriver should be used only for testing purpose.It makes possible to unit test embd i2c functionality
 func SetI2cDriver(drv I2CDriver, initialized bool) {
 	i2cDriverInstance = drv
 	i2cDriverInitialized = initialized