Merge remote-tracking branch 'layered/test-groups' into overlayfs-store

doc/manual/src/contributing/testing.md

@@ -14,6 +14,8 @@ You can run the whole testsuite with `make check`, or the tests for a specific c
 The functional tests reside under the `tests` directory and are listed in `tests/local.mk`.
 Each test is a bash script.
 
+### Running the whole test suite
+
 The whole test suite can be run with:
 
 ```shell-session
@@ -23,6 +25,32 @@ ran test tests/bar.sh... [PASS]
 ...
 ```
 
+### Grouping tests
+
+Sometimes it is useful to group related tests so they can be easily run together without running the entire test suite.
+For example, `tests/ca/local.mk` defines a "ca" test group for tests relating to content-addressed derivation outputs.
+
+That test group can be run like this:
+
+```shell-session
+$ make ca.test-group -j50
+ran test tests/ca/nix-run.sh... [PASS]
+ran test tests/ca/import-derivation.sh... [PASS]
+...
+```
+
+The testgroup is defined in Make like this:
+```makefile
+$(test-group-name)-tests := \
+  $(d)/test0.sh \
+  $(d)/test1.sh \
+  ...
+
+install-tests-groups += $(test-group-name)
+```
+
+### Running individual tests
+
 Individual tests can be run with `make`:
 
 ```shell-session