diff --git a/bindings/nodejs/package.json b/bindings/nodejs/package.json
index 83e24ec1..e895a74f 100644
--- a/bindings/nodejs/package.json
+++ b/bindings/nodejs/package.json
@@ -71,7 +71,7 @@
     "url": "git+https://github.com/gorules/zen.git"
   },
   "scripts": {
-    "build": "napi build --dts false --platform --release",
+    "build": "napi build --dts temp.d.ts --platform --release && rm temp.d.ts",
     "build:debug": "napi build --platform --js index.js --dts index.d.ts",
     "watch": "cargo watch --ignore '{index.js,index.d.ts}' -- npm run build:debug",
     "test": "jest",
diff --git a/test-data/graphs/expression-default.json b/test-data/graphs/expression-default.json
new file mode 100644
index 00000000..c5fb8940
--- /dev/null
+++ b/test-data/graphs/expression-default.json
@@ -0,0 +1,93 @@
+{
+  "tests": [
+    {
+      "input": {
+        "a": 1,
+        "b": 2,
+        "extra": "This should not pass through"
+      },
+      "output": {
+        "sum": 3
+      }
+    },
+    {
+      "input": {
+        "a": 5,
+        "b": 3,
+        "sum": 100
+      },
+      "output": {
+        "sum": 8
+      }
+    },
+    {
+      "input": {
+        "a": 10,
+        "b": 20,
+        "c": 30,
+        "d": 40
+      },
+      "output": {
+        "sum": 30
+      }
+    },
+    {
+      "input": {
+        "a": 7,
+        "b": 3,
+        "passThrough": "This should not appear in output"
+      },
+      "output": {
+        "sum": 10
+      }
+    },
+    {
+      "input": {
+        "a": -5,
+        "b": 5,
+        "negative": true
+      },
+      "output": {
+        "sum": 0
+      }
+    }
+  ],
+  "nodes": [
+    {
+      "type": "inputNode",
+      "id": "deced339-bace-452a-8db0-777f038bffe8",
+      "name": "request",
+      "position": {
+        "x": 145,
+        "y": 235
+      }
+    },
+    {
+      "type": "expressionNode",
+      "content": {
+        "expressions": [
+          {
+            "id": "d54641c2-5f24-4140-a9c4-8453542a622a",
+            "key": "sum",
+            "value": "a + b"
+          }
+        ],
+        "passThrough": false
+      },
+      "id": "6b9cfc7e-4776-4b3f-8a19-c2a4d7874770",
+      "name": "expression1",
+      "position": {
+        "x": 475,
+        "y": 235
+      }
+    }
+  ],
+  "edges": [
+    {
+      "id": "639f3a3a-7545-4e98-aa79-7a9bd9644af1",
+      "sourceId": "deced339-bace-452a-8db0-777f038bffe8",
+      "type": "edge",
+      "targetId": "6b9cfc7e-4776-4b3f-8a19-c2a4d7874770"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/test-data/graphs/expression-fields.json b/test-data/graphs/expression-fields.json
new file mode 100644
index 00000000..18df3783
--- /dev/null
+++ b/test-data/graphs/expression-fields.json
@@ -0,0 +1,94 @@
+{
+  "tests": [
+    {
+      "input": {
+        "customer": {
+          "firstName": "John",
+          "lastName": "Doe",
+          "age": 30
+        },
+        "order": {
+          "id": "ORD-001",
+          "total": 100
+        }
+      },
+      "output": {
+        "customer": {
+          "firstName": "John",
+          "lastName": "Doe",
+          "age": 30,
+          "fullName": "John Doe"
+        },
+        "order": {
+          "id": "ORD-001",
+          "total": 100
+        }
+      }
+    },
+    {
+      "input": {
+        "customer": {
+          "firstName": "Jane",
+          "lastName": "Smith",
+          "age": 25
+        },
+        "order": {
+          "id": "ORD-002",
+          "total": 150
+        }
+      },
+      "output": {
+        "customer": {
+          "firstName": "Jane",
+          "lastName": "Smith",
+          "age": 25,
+          "fullName": "Jane Smith"
+        },
+        "order": {
+          "id": "ORD-002",
+          "total": 150
+        }
+      }
+    }
+  ],
+  "nodes": [
+    {
+      "type": "inputNode",
+      "id": "input-node",
+      "name": "request",
+      "position": {
+        "x": 100,
+        "y": 100
+      }
+    },
+    {
+      "type": "expressionNode",
+      "id": "expression-node-1",
+      "name": "customerFullName",
+      "position": {
+        "x": 300,
+        "y": 100
+      },
+      "content": {
+        "inputField": "customer",
+        "outputPath": "customer",
+        "expressions": [
+          {
+            "id": "07795ded-cb9b-4165-9b5e-783b066dda61",
+            "key": "fullName",
+            "value": "`${firstName} ${lastName}`"
+          }
+        ],
+        "passThrough": true
+      }
+    }
+  ],
+  "edges": [
+    {
+      "id": "edge-1",
+      "sourceId": "input-node",
+      "targetId": "expression-node-1",
+      "type": "edge"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/test-data/graphs/expression-loop.json b/test-data/graphs/expression-loop.json
new file mode 100644
index 00000000..29d48e2b
--- /dev/null
+++ b/test-data/graphs/expression-loop.json
@@ -0,0 +1,94 @@
+{
+  "tests": [
+    {
+      "input": {
+        "cart": {
+          "items": [
+            {
+              "name": "Apple",
+              "price": 0.5,
+              "quantity": 3
+            },
+            {
+              "name": "Banana",
+              "price": 0.3,
+              "quantity": 5
+            },
+            {
+              "name": "Orange",
+              "price": 0.7,
+              "quantity": 2
+            }
+          ],
+          "customerId": "CUST-001"
+        }
+      },
+      "output": {
+        "cart": {
+          "items": [
+            {
+              "name": "Apple",
+              "price": 0.5,
+              "quantity": 3,
+              "totalPrice": 1.5
+            },
+            {
+              "name": "Banana",
+              "price": 0.3,
+              "quantity": 5,
+              "totalPrice": 1.5
+            },
+            {
+              "name": "Orange",
+              "price": 0.7,
+              "quantity": 2,
+              "totalPrice": 1.4
+            }
+          ],
+          "customerId": "CUST-001"
+        }
+      }
+    }
+  ],
+  "nodes": [
+    {
+      "type": "inputNode",
+      "id": "input-node",
+      "name": "request",
+      "position": {
+        "x": 100,
+        "y": 100
+      }
+    },
+    {
+      "type": "expressionNode",
+      "id": "expression-node-1",
+      "name": "calculateItemTotal",
+      "position": {
+        "x": 300,
+        "y": 100
+      },
+      "content": {
+        "inputField": "cart.items",
+        "outputPath": "cart.items",
+        "executionMode": "loop",
+        "expressions": [
+          {
+            "id": "total-price-exp",
+            "key": "totalPrice",
+            "value": "price * quantity"
+          }
+        ],
+        "passThrough": true
+      }
+    }
+  ],
+  "edges": [
+    {
+      "id": "edge-1",
+      "sourceId": "input-node",
+      "targetId": "expression-node-1",
+      "type": "edge"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/test-data/graphs/expression-passthrough.json b/test-data/graphs/expression-passthrough.json
new file mode 100644
index 00000000..1b8bf907
--- /dev/null
+++ b/test-data/graphs/expression-passthrough.json
@@ -0,0 +1,108 @@
+{
+  "tests": [
+    {
+      "input": {
+        "a": 1,
+        "b": 2,
+        "sum": []
+      },
+      "output": {
+        "a": 1,
+        "b": 2,
+        "sum": 3
+      }
+    },
+    {
+      "input": {
+        "a": 5,
+        "b": 3,
+        "sum": 100
+      },
+      "output": {
+        "a": 5,
+        "b": 3,
+        "sum": 8
+      }
+    },
+    {
+      "input": {
+        "a": 10,
+        "b": 20,
+        "extra": "This should pass through"
+      },
+      "output": {
+        "a": 10,
+        "b": 20,
+        "sum": 30,
+        "extra": "This should pass through"
+      }
+    },
+    {
+      "input": {
+        "a": 7,
+        "b": 3,
+        "sum": "Original",
+        "passThrough": "Test"
+      },
+      "output": {
+        "a": 7,
+        "b": 3,
+        "sum": 10,
+        "passThrough": "Test"
+      }
+    },
+    {
+      "input": {
+        "a": 1,
+        "b": 1,
+        "c": 3,
+        "d": 4
+      },
+      "output": {
+        "a": 1,
+        "b": 1,
+        "c": 3,
+        "d": 4,
+        "sum": 2
+      }
+    }
+  ],
+  "nodes": [
+    {
+      "type": "inputNode",
+      "id": "deced339-bace-452a-8db0-777f038bffe8",
+      "name": "request",
+      "position": {
+        "x": 145,
+        "y": 235
+      }
+    },
+    {
+      "type": "expressionNode",
+      "content": {
+        "expressions": [
+          {
+            "id": "d54641c2-5f24-4140-a9c4-8453542a622a",
+            "key": "sum",
+            "value": "a + b"
+          }
+        ],
+        "passThrough": true
+      },
+      "id": "6b9cfc7e-4776-4b3f-8a19-c2a4d7874770",
+      "name": "expression1",
+      "position": {
+        "x": 475,
+        "y": 235
+      }
+    }
+  ],
+  "edges": [
+    {
+      "id": "639f3a3a-7545-4e98-aa79-7a9bd9644af1",
+      "sourceId": "deced339-bace-452a-8db0-777f038bffe8",
+      "type": "edge",
+      "targetId": "6b9cfc7e-4776-4b3f-8a19-c2a4d7874770"
+    }
+  ]
+}
\ No newline at end of file