Basic-usage.md

-## Configure the testsuite:
+## Configure the testsuite
 
 You will need to perform this operation each time you clone a new testsuite, or if the configuration format has changed. An error message during the testsuite execution will show you if you have to configure the testsuite again.
 
@@ -6,8 +6,64 @@ You will need to perform this operation each time you clone a new testsuite, or
 ./ts configure
 ```
 
-### Run the testsuite:
+## Run the testsuite
+
+This command will run the whole testsuite. Your need to keep your machine connected to internet to run the testsuite, since jobs are created dynamically on marenostrum.
 
 ```sh
 ./ts all
 ```
+
+## Configure and run a small testsuite
+
+If you don't know which builds to select, or if you want to try a testsuite on a new branch of alya for the first time, we advise you to run a small testsuite, either on marenostrum (standard) or power9 (faster, but you need specific access to this machine).
+
+Configure the testsuite as usual (if necessary):
+
+```sh
+./ts configure
+```
+
+If you had previously configured the testsuite and just need to pick another branch:
+
+```sh
+./ts configure -ab [branch-name]
+```
+
+Then, configure the type of small testsuite. This option will select the most appropriate build and set the job queues optimally.
+
+Marenostrum build:
+
+```sh
+./ts configure --small-mn
+```
+
+Power9 build:
+
+```sh
+./ts configure --small-p9
+```
+
+Then, run the testsuite as usual:
+
+```sh
+./ts all
+```
+
+## Run a subset of tests
+
+To reduce even more the testsuite size, you can run it by defining a subset of tests only.
+
+The option `-t` enables to specify a list of tests (separated by a space) to run
+
+```sh
+./ts all -t test1 test2 test3
+```
+
+The option `-d` enables to specify a list of subdirectories of the alya directory `tests`:
+
+```sh
+./ts all -d subdir1 subdir2 subdir3
+```
+
+You can cumulate both `-t` and `-d`. The tests which will be selected will be the conjunction between both options.