Initial version of unit testing documentation

This commit includes the 'User guide' and 'Implementing tests' sections
for helping people building, running and writing unit tests. A more
detailed version of documentation is available under the 'Component
user manuals section'.

Change-Id: I67e93ac805d1f4e7727964f3d95a70436ae34733
Signed-off-by: Imre Kis <imre.kis@arm.com>
diff --git a/docs/resources/sequence_print_to_eeprom.puml b/docs/resources/sequence_print_to_eeprom.puml
new file mode 100644
index 0000000..3f8c108
--- /dev/null
+++ b/docs/resources/sequence_print_to_eeprom.puml
@@ -0,0 +1,39 @@
+@startuml
+participant Application as APP
+
+activate APP
+APP -> Print: print_to_eeprom(fmt, ...)
+activate Print
+
+	Print -> EEPROM: eeprom_write(buffer)
+	activate EEPROM
+
+		EEPROM -> I2C: i2c_write(address, buffer)
+		activate I2C
+
+			I2C -> Hardware: I2C transaction
+			activate Hardware
+			Hardware --> I2C: ack/nack
+			deactivate Hardware
+
+		I2C --> EEPROM: result
+		deactivate I2C
+
+		EEPROM -> I2C: i2c_write(address, buffer+ result)
+		activate I2C
+
+			I2C -> Hardware: I2C transaction
+			activate Hardware
+			Hardware --> I2C: ack/nack
+			deactivate Hardware
+
+		I2C --> EEPROM: result
+		deactivate I2C
+
+	EEPROM --> Print: result
+	deactivate EEPROM
+
+Print -> APP: result
+deactivate Print
+
+@enduml
\ No newline at end of file