diff --git a/.github/workflows/test-cases.yml b/.github/workflows/test-cases.yml
index f5279b2..94a6e1b 100644
--- a/.github/workflows/test-cases.yml
+++ b/.github/workflows/test-cases.yml
@@ -11,10 +11,10 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Use Node.js 18.x
+      - name: Use Node.js 20.x
         uses: actions/setup-node@v3
         with:
-          node-version: 18.x
+          node-version: 20.x
 
       - name: Install heta-compiler
         run: |
diff --git a/cases/0005/index0.heta b/cases/0005/index0.heta
index e7d637d..748e394 100644
--- a/cases/0005/index0.heta
+++ b/cases/0005/index0.heta
@@ -2,5 +2,7 @@
     Create reaction in Heta notation with one substrate and one product.
 */
 
+#setNS nameless {type: abstract};
+
 // reaction of s1 degradation
 r1 @Reaction {actors: s1 => p1} := k1 * s1 * comp1;
diff --git a/cases/0006/index0.heta b/cases/0006/index0.heta
index 816191a..b798c4b 100644
--- a/cases/0006/index0.heta
+++ b/cases/0006/index0.heta
@@ -2,5 +2,7 @@
   Create reaction with no substrate and one product in Heta.
 */
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: => p1} := k1 * comp1;
diff --git a/cases/0006/index1.heta b/cases/0006/index1.heta
index 073a821..1464c69 100644
--- a/cases/0006/index1.heta
+++ b/cases/0006/index1.heta
@@ -2,6 +2,8 @@
   Add necessary species
 */
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: => p1} := k1 * comp1;
 
diff --git a/cases/0007/index0.heta b/cases/0007/index0.heta
index 741806c..368ce5e 100644
--- a/cases/0007/index0.heta
+++ b/cases/0007/index0.heta
@@ -2,6 +2,8 @@
   Create mass-action reaction in Heta notation by the stoicheometry: s1 => p1.
 */
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: s1 => p1} := k1 * s1 * comp1;
 
diff --git a/cases/0008/index0.heta b/cases/0008/index0.heta
index 4bd25ab..4026ed9 100644
--- a/cases/0008/index0.heta
+++ b/cases/0008/index0.heta
@@ -2,5 +2,7 @@
   Create mass-action reaction in Heta notation by the stoicheometry: 2s1 => p1.
 */
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: 2s1 => p1} := k1 * s1^2 * comp1;
diff --git a/cases/0008/index1.heta b/cases/0008/index1.heta
index 7bebaaf..f2d0d50 100644
--- a/cases/0008/index1.heta
+++ b/cases/0008/index1.heta
@@ -2,5 +2,7 @@
   Make reaction reversible
 */
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: 2s1 <=> p1} := (k1 * s1^2 - k2 * p1) * comp2;
diff --git a/cases/0009/index0.heta b/cases/0009/index0.heta
index c9078be..e5bcec2 100644
--- a/cases/0009/index0.heta
+++ b/cases/0009/index0.heta
@@ -3,5 +3,7 @@
 */
 // index.heta
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: 2s1 => p1} := (k1 * s1^2 - k2 * p1^2) * comp1;
diff --git a/cases/0010/index0.heta b/cases/0010/index0.heta
index 5bad0e2..2693016 100644
--- a/cases/0010/index0.heta
+++ b/cases/0010/index0.heta
@@ -3,5 +3,7 @@
 */
 // index.heta
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: s1 + 2s2 + 3s3 <=> p1 + 2p2 + 3p3} := (k1 * s1 * s2^2 * s3^3 - k2 * p1 * p2^2 * p3^3) * comp1;
diff --git a/cases/0012/index0.heta b/cases/0012/index0.heta
index 4967bce..bf84919 100644
--- a/cases/0012/index0.heta
+++ b/cases/0012/index0.heta
@@ -4,6 +4,8 @@
     x1 + x4 <=> x5
 */
 
+#setNS nameless {type: abstract};
+
 // reactions
 r1 @Reaction {actors: x1 + 3x2 <=> x3} := (k1 * x1 * x2^3 - k2 * x3) * comp1;
 r2 @Reaction {actors: x1 + x4 <=> x5} := (k3 * x1 * x4 - k4 * x5) * comp1;