docs: inform how to run tests locally (#675)

test/README.md

@@ -7,7 +7,7 @@ since developer may run on ARM64 architecture. Some of the snapshot tests are ar
 running them on an ARM64 machine will result in different values than for x86_64. This is due to Delanay 
 triangulation algorithm used in some of the compressor calculations.
 
-## Running tests
+## Running tests in Docker (STP/LTP snapshot tests)
 
 Since running tests in a container is only required for some of the tests, the default setup is already
 configured in *docker-compose.yml* file. To run tests, simply run (from test/ dir):
@@ -25,6 +25,14 @@ docker compose up
 This will build the container and run the tests marked 'dockersnapshot'. If the snapshot has changed, it will fail with exit code 1, and
 update snapshots. Rerun the test again, with the command above, to make sure it passes.
 
+## Running tests locally (ie not docker)
+
+Run all tests except the STP/LTP snapshot tests (for now), and skip future tests we need to run in Docker:
+
+```
+pytest [other_args] --snapshot-update -m "not dockersnapshot"
+```
+
 ## Alternative test
 
 If you want to run the dockersnapshot tests and update snapshots without docker compose, and ad-hoc, you can run the following command, from libecalc root: