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+# `testing_buildBlockV1`
+
+This document specifies the `testing_buildBlockV1` RPC method. This method is a debugging and testing tool that simplifies the block production process into a single call. It is intended to replace the multi-step workflow of sending transactions, calling `engine_forkchoiceUpdated` with `payloadAttributes`, and then calling `engine_getPayload`.
+
+This method is considered sensitive and is intended for testing environments only. See [**Security Considerations**](#security-considerations) for more details.
+
+### Request
+
+* method: `testing_buildBlockV1`
+* params:
+  1. `parentBlockHash`: `DATA`, 32 Bytes - block hash of the parent of the requested block.
+  2. `payloadAttributes`: `Object` - instance of [`PayloadAttributesV3`](../engine/cancun.md#payloadattributesv3)
+  3. `transactions`: `Array of DATA` - an array of raw, signed transactions (hex-encoded `0x...` strings) to forcibly include in the generated block.
+  4. `extraData`: `DATA|null`, 0 to 32 Bytes - data to be set as the `extraData` field of the built block.
+
+### Response
+
+* result: `OBJECT` - instance of [`engine_getPayloadV5`](../engine/osaka.md#response)
+* error: code and message set in case an exception happens while building the requested block.
+
+### Specification
+
+* The client MUST build a new execution payload using the block specified by `parentBlockHash` as its parent.
+
+* The client MUST use the provided `payloadAttributes` to define the context of the new block.
+
+* The client MUST include all transactions from the `transactions` array on the block's transaction list, in the order they were provided.
+
+* The client MUST NOT include any transactions from its local transaction pool. The resulting block MUST only contain the transactions specified in the `transactions` array.
+
+* If `extraData` is provided, the client MUST set the `extraData` field of the resulting payload to this value.
+
+* This method MUST NOT modify the client's canonical chain or head block. It is a read-only method for payload generation.
+
+### Security Considerations
+
+* **HIGHLY SENSITIVE**: This method is a powerful debugging tool intended for testing environments ONLY.
+
+* It allows for the creation of arbitrary blocks. It can be in used to forcibly include any valid transaction.
+
+* This method MUST NOT be exposed on public-facing RPC APIs.
+
+* It is strongly recommended that this method, and its `testing_` namespace, be disabled by default. Enabling it should require an explicit command-line flag or configuration setting by the node operator.
+
+### Example
+
+#### Request
+
+```json
+{
+  "id": 1,
+  "jsonrpc": "2.0",
+  "method": "testing_buildBlockV1",
+  "params": [
+    {
+      "parentBlockHash": "0x3b8fb240d288781d4f1e1d32f4c1550BEEFDEADBEEFDEADBEEFDEADBEEFDEAD",
+      "payloadAttributes": {
+        "timestamp": "0x6705D918",
+        "prevRandao": "0x0000000000000000000000000000000000000000000000000000000000000000",
+        "suggestedFeeRecipient": "0x0000000000000000000000000000000000000000",
+        "withdrawals": [],
+        "parentBeaconBlockRoot": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884365149a42212e8822"
+      },
+      "transactions": [
+        "0xf86c0a8504a817c80082520894...cb61163c917540a0c64c12b8f50015",
+        "0xf86b0f8504a817c80082520894...5443c01e69d3b0c5112101564914a2"
+      ],
+      "extraData": "0x746573745F6E616D65"
+    }
+  ]
+}
+```
+
+#### Response (Success)
+
+```json
+{
+  "id": 1,
+  "jsonrpc": "2.0",
+  "result": {
+    "executionPayload": {
+      "blockHash": "0x8980a3a7f8b16053c4dec86e1050e6378e176272517852f8c5b56f34e9a0f9b6",
+      "parentHash": "0x3b8fb240d288781d4f1e1d32f4c15509a2b7538b8e0e719541a50a31a2631a01",
+      "feeRecipient": "0x0000000000000000000000000000000000000000",
+      "stateRoot": "0xca3699d05d3369680315af1d03c6f8f73188945f3c83756bde2575ddc25c6040",
+      "receiptsRoot": "0x2e0617b0c3545d1668e8d8cb530a6c71b0a8f82875b1d0b38c352718016feff6",
+      "logsBloom": "0x00...00",
+      "prevRandao": "0x0000000000000000000000000000000000000000000000000000000000000000",
+      "blockNumber": "0x1b4",
+      "gasLimit": "0x1c9c380",
+      "gasUsed": "0xa410",
+      "timestamp": "0x6705D918",
+      "extraData": "0x746573745F6E616D65",
+      "baseFeePerGas": "0x7",
+      "excessBlobGas": "0x0",
+      "blobGasUsed": "0x0",
+      "transactions": [
+        "0xf86c0a8504a817c80082520894...cb61163c917540a0c64c12b8f50015",
+        "0xf86b0f8504a817c80082520894...5443c01e69d3b0c5112101564914a2"
+      ],
+      "parentBeaconBlockRoot": "0xcf8e0d4e9587369b2301d0790347320302cc0943d5a1884365149a42212e8822",
+      "depositRequests": [],
+      "consolidationRequests": []
+    },
+    "blockValue": "0x1b681a965684000",
+    "blobsBundle": {
+      "commitments": [],
+      "blobs": [],
+      "kzgProofs": []
+    },
+    "shouldOverrideBuilder": false,
+    "executionRequests": []
+  }
+}
+```