Separate test stage + Limit to one core

.gitlab-ci.yml

@@ -2,7 +2,7 @@ stages:
   - format
   - build
   - lint
-  # - test
+  - test
   - image
 
 .rust_template: &rust_template
@@ -23,14 +23,13 @@ rust-nightly:
   <<: *rust_template
   script:
     - cargo build --verbose
-    - cargo test --verbose
 
-# rust-nightly-test:
-#   stage: test
-#   image: rustlang/rust:nightly
-#   <<: *rust_template
-#   script:
-#     - cargo test --verbose
+rust-nightly-test:
+  stage: test
+  image: rustlang/rust:nightly
+  <<: *rust_template
+  script:
+    - cargo test --verbose -j 1
 
 rust-nightly-fmt:
   stage: format