Document installability test (#1037)

Document installability test

Related to packit/packit-service#2782.

Reviewed-by: Laura Barcziová

Author: softwarefactory-project-zuul[bot]

docs/configuration/upstream/copr_build.md

@@ -156,7 +156,7 @@ packages and modules from the base distro, while CentOS Stream 8 will use a
 custom yum repo, 4 specific modules and it will have `--without check` passed
 to rpmbuild.
 
-You can define these three options:
+You can define these options:
 * `additional_packages` (list) – install additional packages before the build
 * `additional_repos` (list) – enable these yum repositories before installing any packages
 * `additional_modules` (str) – enable these modules before installing packages,

fedora-ci/jobs.md

@@ -11,7 +11,8 @@ Scratch builds in [Koji](https://koji.fedoraproject.org/koji/) built from SCM.
 
 ### Installability
 
-TBD (The work is in progress.)
+[Installability test](https://github.com/fedora-ci/installability-pipeline)
+in [Testing Farm](https://testing-farm.io) run with a successfull scratch build.
 
 ### Custom test plans
 

fedora-ci/retriggering.md

@@ -14,3 +14,22 @@ To retrigger a scratch build, add the following comment to the pull request:
 ```
 
 Only packagers can retrigger scratch builds.
+
+## Tests
+
+To retrigger all tests, add the following comment to the pull request:
+
+```
+/packit-ci test
+```
+
+To retrigger a specific test, you can add the test identifier to the command:
+
+```
+/packit-ci test installability
+```
+
+`installability` is the only supported identifier so far and it represents
+the [Installability](fedora-ci/jobs#installability) test.
+
+Only packagers can retrigger tests.