diff --git a/tests/digraph/t0_fewnodes.nim b/tests/digraph/t0_fewnodes.nim
index f8bfe6a..cd05b9d 100644
--- a/tests/digraph/t0_fewnodes.nim
+++ b/tests/digraph/t0_fewnodes.nim
@@ -3,9 +3,10 @@ discard """
   action: "run"
   batchable: true
   joinable: true
-  timeout: 2.0
+  timeout: 10.0
   targets: "c cpp js objc"
-  matrix: "; -d:release; -d:danger"
+  valgrind: on
+  matrix: "-d:useMalloc"
 """
 
 import
diff --git a/tests/digraph/t1_manynodes.nim b/tests/digraph/t1_manynodes.nim
index 839c51a..343b663 100644
--- a/tests/digraph/t1_manynodes.nim
+++ b/tests/digraph/t1_manynodes.nim
@@ -3,9 +3,10 @@ discard """
   action: "run"
   batchable: true
   joinable: true
-  timeout: 20.0
+  timeout: 40.0
   targets: "c cpp js objc"
-  matrix: "; -d:release; -d:danger"
+  valgrind: on
+  matrix: "-d:useMalloc"
 """
 
 import
diff --git a/tests/digraph/t2_cycles.nim b/tests/digraph/t2_cycles.nim
index 11d68e0..4ac8c32 100644
--- a/tests/digraph/t2_cycles.nim
+++ b/tests/digraph/t2_cycles.nim
@@ -3,9 +3,10 @@ discard """
   action: "run"
   batchable: true
   joinable: true
-  timeout: 2.0
+  timeout: 10.0
   targets: "c cpp js objc"
-  matrix: "; -d:release; -d:danger"
+  valgrind: on
+  matrix: "-d:useMalloc"
 """
 
 ##[This test verifies that the cycle detection algorithms correctly identify
@@ -46,7 +47,33 @@ block simple:
   doAssert myDig.hasTwoCycle(Kahns)
   doAssert myDig.hasTwoCycle(PathBasedStrongComponent)
 
+block loop:
+  var myDig = DiGraph[int]()
+  with myDig:
+    inclEdge 1, 2
+    inclEdge 2, 3
+    inclEdge 3, 4
+    inclEdge 4, 5
+
+    inclEdge 3, 5
+
+    inclEdge 10, 2
+
+    inclEdge 55, 2
 
+  # Verify that the graph currently has no cycles
+  doAssert not myDig.hasCycle
+  doAssert not myDig.hasLoop
+  doAssert not myDig.hasTwoCycle(Kahns)
+  doAssert not myDig.hasTwoCycle(PathBasedStrongComponent)
+
+  myDig.inclEdge 5, 5 # Add an edge from node 5 to node 5, creating a loop
+
+  # Verify that the graph now contains a cycle
+  doAssert myDig.hasCycle
+  doAssert not myDig.hasTwoCycle(Kahns)
+  doAssert not myDig.hasTwoCycle(PathBasedStrongComponent)
+  doAssert myDig.hasLoop
 
 block complex:
   var complexDigraph = DiGraph[int]()
diff --git a/tests/digraph/t3_simpleIterators.nim b/tests/digraph/t3_simpleIterators.nim
index ead33b5..1babaff 100644
--- a/tests/digraph/t3_simpleIterators.nim
+++ b/tests/digraph/t3_simpleIterators.nim
@@ -5,7 +5,8 @@ discard """
   joinable: true
   timeout: 2.0
   targets: "c cpp js objc"
-  matrix: "; -d:release; -d:danger"
+  valgrind: on
+  matrix: "-d:useMalloc"
 """
 
 import
diff --git a/tests/digraph/t4_walkFrom.nim b/tests/digraph/t4_walkFrom.nim
index 1d63430..c5d21ba 100644
--- a/tests/digraph/t4_walkFrom.nim
+++ b/tests/digraph/t4_walkFrom.nim
@@ -5,7 +5,8 @@ discard """
   joinable: true
   timeout: 5.0
   targets: "c cpp js objc"
-  matrix: "; -d:release; -d:danger"
+  valgrind: on
+  matrix: "-d:useMalloc"
 """
 
 import
diff --git a/tests/digraph/t5_properties.nim b/tests/digraph/t5_properties.nim
index b9531c9..dd82319 100644
--- a/tests/digraph/t5_properties.nim
+++ b/tests/digraph/t5_properties.nim
@@ -5,7 +5,8 @@ discard """
   joinable: true
   timeout: 5.0
   targets: "c cpp js objc"
-  matrix: "; -d:release; -d:danger"
+  valgrind: on
+  matrix: "-d:useMalloc"
 """
 
 import
diff --git a/tests/unsafetables/tests.nim b/tests/unsafetables/tests.nim
index d8908a2..d43ccde 100644
--- a/tests/unsafetables/tests.nim
+++ b/tests/unsafetables/tests.nim
@@ -5,7 +5,8 @@ discard """
   joinable: true
   timeout: 2.0
   targets: "c cpp js objc"
-  matrix: ""
+  valgrind: on
+  matrix: "-d:useMalloc"
 """
 
 import