│   app.js
│   compile.js
│   deploy.js
│   routes.js
│   truffle-config.js
│
├───build
│   └───contracts
│           A.json
│           Migrations.json
│           U.json
│
├───contracts
│       A.sol
│       Migrations.sol
│       U.sol
│
├───migrations
│       1_initial_migration.js
│       2_deploy.js
│
└───test

npm i express path fs solc ethereumjs-tx web3-utils web3@0.20.7 morgan

truffle(development)> let a = await A.deployed()
undefined
truffle(development)> a.getTotalCount()
<BN: 0>
truffle(development)> a.add(12)
{ tx:
   '0xfa53d1aac439dbdfea4b004410ebca35275a5f4377b54f64f9ab52388a08e0bf',
  receipt:
   { transactionHash:
      '0xfa53d1aac439dbdfea4b004410ebca35275a5f4377b54f64f9ab52388a08e0bf',
     transactionIndex: 0,
     blockHash:
      '0xe743d66e3cb5bf15ac741e9a1efd869249c2eed52ab63f8efc6233b35661fc1b',
     blockNumber: 164,
     from: '0x07df0e5ab4793197007a867d97a3aeeea5347456',
     to: '0x8b421f5c74b48e0f6ae763702754ce172deeb293',
     gasUsed: 47006,
     cumulativeGasUsed: 47006,
     contractAddress: null,
     logs: [],
     status: true,
     logsBloom:
      '0x00...//intentional',
     v: '0x1c',
     r:
      '0xd2ac433f565e69e3587d07ebd3fe00a14204add708a47cfbc6406d2c092061f2',
     s:
      '0x7f7f6a80f6d67199b88cc2cde924a0c2c39421aadb29201661891bf03b346219',
     rawLogs: [] },
  logs: [] }
truffle(development)> a.getTotalCount()
<BN: 1>
truffle(development)>

GET /d 200 4051.218 ms - 12
Error: VM Exception while processing transaction: invalid opcode
    at Object.InvalidResponse (D:assignmentsblockchainassignassignmentsblockchainsrcanarik-4anarik-v5.0src_3anarik-v5.0.2testsmartContractsolcnode_modulesweb3libweb3errors.js:38:16)
    at D:assignmentsblockchainassignassignmentsblockchainsrcanarik-4anarik-v5.0src_3anarik-v5.0.2testsmartContractsolcnode_modulesweb3libweb3requestmanager.js:86:36
    at XMLHttpRequest.request.onreadystatechange (D:assignmentsblockchainassignassignmentsblockchainsrcanarik-4anarik-v5.0src_3anarik-v5.0.2testsmartContractsolcnode_modulesweb3libweb3httpprovider.js:129:7)
    at XMLHttpRequestEventTarget.dispatchEvent (D:assignmentsblockchainassignassignmentsblockchainsrcanarik-4anarik-v5.0src_3anarik-v5.0.2testsmartContractsolcnode_modulesxhr2-cookiesdistxml-http-request-event-target.js:34:22)
    at XMLHttpRequest._setReadyState (D:assignmentsblockchainassignassignmentsblockchainsrcanarik-4anarik-v5.0src_3anarik-v5.0.2testsmartContractsolcnode_modulesxhr2-cookiesdistxml-http-request.js:208:14)
    at XMLHttpRequest._onHttpResponseEnd (D:assignmentsblockchainassignassignmentsblockchainsrcanarik-4anarik-v5.0src_3anarik-v5.0.2testsmartContractsolcnode_modulesxhr2-cookiesdistxml-http-request.js:318:14)
    at IncomingMessage.<anonymous> (D:assignmentsblockchainassignassignmentsblockchainsrcanarik-4anarik-v5.0src_3anarik-v5.0.2testsmartContractsolcnode_modulesxhr2-cookiesdistxml-http-request.js:289:61)
    at IncomingMessage.emit (events.js:187:15)
    at endReadableNT (_stream_readable.js:1094:12)
    at process._tickCallback (internal/process/next_tick.js:63:19) null
_http_outgoing.js:470
    throw new ERR_HTTP_HEADERS_SENT('set');
    ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (_http_outgoing.js:470:11)

> truffle version
Truffle v5.0.2 (core: 5.0.2)
Solidity - 0.5.2 (solc-js)
Node v10.14.2

"_id": "solc@0.5.7",