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_mock.puml b/docs/resources/sequence_print_to_eeprom_mock.puml
new file mode 100644
index 0000000..67a4325
--- /dev/null
+++ b/docs/resources/sequence_print_to_eeprom_mock.puml
@@ -0,0 +1,41 @@
+@startuml
+participant "Test case" as TC
+participant "Code under test" as CUT
+
+group Setting expectations
+	activate TC
+	TC -> Mock: expect_write("hello1hello2", 6)
+	activate Mock
+	deactivate Mock
+	TC -> Mock: expect_write("hello2", 6)
+	activate Mock
+	deactivate Mock
+end
+
+TC -> CUT: print_to_eeprom("hello%dhello%d", 1, 2)
+activate CUT
+
+	group Using mocked interface
+		CUT -> Mock: eeprom_write("hello1hello2")
+		activate Mock
+		Mock --> CUT: 6
+		deactivate Mock
+
+		CUT -> Mock: eeprom_write("hello2")
+		activate Mock
+		Mock --> CUT: 6
+		deactivate Mock
+	end
+
+CUT --> TC: 6 + 6 = 12
+deactivate CUT
+
+TC -> Mock: mock().checkExpectation()
+activate Mock
+deactivate Mock
+
+TC -> Mock: mock().clear()
+activate Mock
+deactivate Mock
+
+@enduml
\ No newline at end of file