add a README to tests directory to describe how to run 'make check' (sonic-net#629)

* add a README to tests directory to describe how to run 'make check'

* small spelling and grammar fix

Co-authored-by: Syd Logan <[email protected]>

Author: sydlogan

tests/README.md

@@ -0,0 +1,100 @@
+# Running Tests 
+
+## Overview
+
+Validation scripts that are normally run when a pull request for sonic-sairedis is
+created can be manually run from source by following these steps.
+
+## Start with a clean build
+
+If you don't already have a build, create one.
+
+```
+$ make target/sonic-vs.img.gz
+```
+
+## Running the tests with make check
+
+To run these tests, do the following:
+
+In sonic-buildimage/rules/config, enable KEEP_SLAVE_ON:
+
+```
+KEEP_SLAVE_ON = yes
+```
+
+Then, build (do not make clean, just start a new build). In the following example, 
+primary build is stretch-based at the time of writing:
+
+```
+$ make target/sonic-vs.img.gz
+```
+
+If the build complains nothing to do, remove the target 
+
+```
+$ make target/sonic-vs.img.gz
+make: 'target/sonic-vs.img.gz' is up to date.
+$ rm target/sonic-vs.img.gz
+```
+
+and try again.
+
+The first docker you will drop into is jessie, exit that docker by typing 
+exit at the prompt, and the build will continue with stretch:
+
+```
+make: Nothing to be done for 'jessie'.
+user@1c34bd0395d1:/sonic$ exit
+exit
+make[1]: Leaving directory '/home/slogan/sonic2/sonic-buildimage'
+EXTRA_DOCKER_TARGETS=sonic-vs.img.gz BLDENV=stretch make -f Makefile.work stretch
+make[1]: Entering directory '/home/slogan/sonic2/sonic-buildimage'
+SONiC Build System
+...
+user@288feb4edd39:/sonic$
+```
+
+At this point, some debians from the build need to be installed. Copy and paste the following into 
+a bash script, and execute to install redis, dependency libs, and enable rsyslog logging to aid
+in debugging test script failures. Do this in the docker, in /sonic directory (paths in the 
+script are relative to that location):
+
+```
+sudo dpkg -i target/debs/stretch/libhiredis*.deb
+# Install libnl3
+sudo dpkg -i target/debs/stretch/libnl-3-200_*.deb
+sudo dpkg -i target/debs/stretch/libnl-3-dev_*.deb
+sudo dpkg -i target/debs/stretch/libnl-genl-3-200_*.deb
+sudo dpkg -i target/debs/stretch/libnl-genl-3-dev_*.deb
+sudo dpkg -i target/debs/stretch/libnl-route-3-200_*.deb
+sudo dpkg -i target/debs/stretch/libnl-route-3-dev_*.deb
+sudo dpkg -i target/debs/stretch/libnl-nf-3-200_*.deb
+sudo dpkg -i target/debs/stretch/libnl-nf-3-dev_*.deb
+sudo dpkg -i target/debs/stretch/libnl-cli-3-200_*.deb
+sudo dpkg -i target/debs/stretch/libnl-cli-3-dev_*.deb
+# Install common library
+sudo dpkg -i target/debs/stretch/libswsscommon_*.deb
+sudo dpkg -i target/debs/stretch/libswsscommon-dev_*.deb
+# Install REDIS
+sudo apt-get install -y liblua5.1-0 lua-bitop lua-cjson
+sudo dpkg -i target/debs/stretch/redis-tools_*.deb
+sudo dpkg -i target/debs/stretch/redis-server_*.deb
+sudo sed -ri 's/^# unixsocket/unixsocket/' /etc/redis/redis.conf
+sudo sed -ri 's/^unixsocketperm .../unixsocketperm 777/' /etc/redis/redis.conf
+sudo sed -ri 's/redis-server.sock/redis.sock/' /etc/redis/redis.conf
+sudo service redis-server start
+sudo service rsyslog start
+```
+
+Now you can execute the tests by issuing make check. Failures will be
+reported to the console.
+
+
+```
+user@288feb4edd39:/sonic$ cd src/sonic-sairedis/tests
+user@288feb4edd39:/sonic/src/sonic-sairedis/tests$ make check
+...
+```
+
+Diagnosing failures can be aided by inspecting logs in /var/log/syslog