test: Fix the tests running in CI.

.github/workflows/test.yml

@@ -16,6 +16,33 @@ permissions:
   contents: read
 
 jobs:
+  mutation:
+    runs-on: ubuntu-latest
+    name: Mutation
+    steps:
+      - name: Harden Runner
+        uses: step-security/harden-runner@1b05615854632b887b69ae1be8cbefe72d3ae423 # v2.6.0
+        with:
+          disable-sudo: true
+          egress-policy: block #audit
+          allowed-endpoints: >
+            github.com:443
+
+      - name: Checkout Source
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
+        with:
+          fetch-depth: 0
+
+      - name: Install Go
+        uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0
+        with:
+          go-version: '>= 1.21'
+          cache: true
+
+      - name: Run mutation tests
+        run: |
+          cd ./corefunc && go test -tags=mutation -count=1 -parallel=$(nproc) -timeout 30s -ooze.v=true | grep -v "^[[:lower:]]" | grep -v "^)"
+
   unit:
     runs-on: ubuntu-latest
     name: Unit

corefunc/env_ensure_test.go

@@ -49,6 +49,8 @@ func ExampleEnvEnsure() {
 	fmt.Println(err)
 	// Output:
 	// <nil>
+	// <nil>
+	// <nil>
 	// environment variable MY_ENV_VAR_EMPTY is not defined
 	// environment variable MY_ENV_VAR_NOT_SET is not defined
 }
@@ -75,6 +77,7 @@ func ExampleEnvEnsure_pattern() {
 
 	// Output:
 	// <nil>
+	// <nil>
 	// environment variable AWS_VAULT does not match pattern (non)?prod$
 }