Add log compare test for socket example

Author: Qinghao Shi

tests/README.md

@@ -0,0 +1,12 @@
+# Testing examples
+
+Examples are tested using tool [htrun](https://github.com/ARMmbed/mbed-os-tools/tree/master/packages/mbed-host-tests) and templated print log. 
+
+To run the test, use following command after you build the example:
+```
+mbedhtrun -d D: -p COM4 -m K64F -f .\BUILD\K64F\GCC_ARM\sockets.bin --compare-log tests\sockets.log
+```
+
+
+More details about `htrun` are [here](https://github.com/ARMmbed/htrun#testing-mbed-os-examples).
+

tests/sockets.log

@@ -0,0 +1,9 @@
+Mbed OS Socket example
+Mbed OS version:
+
+IP address: (?:[0-9]{1,3}\.){3}[0-9]{1,3}
+Netmask: (?:[0-9]{1,3}\.){3}[0-9]{1,3}
+Gateway: (?:[0-9]{1,3}\.){3}[0-9]{1,3}
+sent \d+ \[GET \/ HTTP\/\d.\d\]
+recv \d+ \[HTTP\/\d.\d \d+ OK\]
+Done