tester: improve API surface and implement one more test function in lis2mdl driver

Signed-off-by: deadprogram <ron@hybridgroup.com>

tester/i2c.go

@@ -1,27 +1,23 @@
 package tester
 
-import (
-	qt "github.com/frankban/quicktest"
-)
-
 // I2CBus implements the I2C interface in memory for testing.
 type I2CBus struct {
-	C       *qt.C
-	Devices []*I2CDevice
+	c       Failer
+	devices []*I2CDevice
 }
 
 // NewI2CBus returns an I2CBus mock I2C instance that uses c to flag errors
 // if they happen. After creating a I2C instance, add devices
 // to it with addDevice before using NewI2CBus interface.
-func NewI2CBus(c *qt.C) *I2CBus {
+func NewI2CBus(c Failer) *I2CBus {
 	return &I2CBus{
-		C: c,
+		c: c,
 	}
 }
 
 // AddDevice adds a new mock device to the mock I2C bus.
 func (bus *I2CBus) AddDevice(d *I2CDevice) {
-	bus.Devices = append(bus.Devices, d)
+	bus.devices = append(bus.devices, d)
 }
 
 // ReadRegister implements I2C.ReadRegister.
@@ -42,11 +38,11 @@ func (bus *I2CBus) Tx(addr uint16, input, output []byte) error {
 
 // FindDevice returns the device with the given address.
 func (bus *I2CBus) FindDevice(addr uint8) *I2CDevice {
-	for _, dev := range bus.Devices {
-		if dev.Addr == addr {
+	for _, dev := range bus.devices {
+		if dev.Addr() == addr {
 			return dev
 		}
 	}
-	bus.C.Fatalf("invalid device addr %#x passed to i2c bus", addr)
+	bus.c.Fatalf("invalid device addr %#x passed to i2c bus", addr)
 	panic("unreachable")
 }