**/contracts/Migrations.sol**

```solidity
pragma solidity >=0.4.21 <0.6.0;

contract Migrations {
  address public owner;
  uint public last_completed_migration;

  constructor() public {
    owner = msg.sender;
  }

  modifier restricted() {
    if (msg.sender == owner) _;
  }

  function setCompleted(uint completed) public restricted {
    last_completed_migration = completed;
  }

  function upgrade(address new_address) public restricted {
    Migrations upgraded = Migrations(new_address);
    upgraded.setCompleted(last_completed_migration);
  }
}
```

**/contracts/Sandbox.sol**

```solidity
pragma solidity ^0.5.0;
contract Hello {
  int num = 0;
  function set(int newNum) external {
    num = newNum;
  }
  function get() external view returns (int) {
    return num;
  }
}
```

**/migrations/1_initial_migration.js**

```javascript
const Migrations = artifacts.require("Migrations");

module.exports = function(deployer) {
  deployer.deploy(Migrations);
};
```

**migrations/1_deploy_contracts.js**

```javascriptconst Hello = artifacts.require("Hello");

module.exports = function(deployer) {
  deployer.deploy(Hello);
};
```

**/test/Hello.js**

```javascript
const Hello = artifacts.require("./Hello.sol");
contract("Hello", accounts => {
    it("unit test 1", async () => {
        const hello = await Hello.deployed();
        const actual = await hello.get.call();
        console.log("(unit test 1) The value is " + actual);
    });
    it("unit test 2", async () => {
        const hello = await Hello.deployed();
        await hello.set(5, {from : accounts[0]});
        console.log("(unit test 2) Setting value to 5.");
    });
    it("unit test 3", async () => {
        const hello = await Hello.deployed();
        const actual = await hello.get.call();
        console.log("(unit test 3) The value is " + actual);
    });
});
```

And I've left **truffle-config.js** blank.

When I run `truffle develop` then `compile`, `migrate`, `test` the output is

```
  Contract: Hello
(unit test 1) The value is 0
    ✓ unit test 1
(unit test 2) Setting value to 5.
    ✓ unit test 2
(unit test 3) The value is 5
    ✓ unit test 3
```

Showing truffle persists state between unit tests.