SOLIDITY UNIT TESTS

Solidity test contracts live alongside Javascript tests as .sol files. When truffle test is run, they will be included in the mocha run with a separate test suite per test contract. These contracts maintain all the benefits of the Javascript tests: namely a clean slate per test suite, access to deployed contracts via migrations, runnable on any Ethereum client, and usage of snapshot/revert features (if supported by your Ethereum client) for increased speed. An example solidity unit test looks like this:

import "truffle/Assert.sol";
import "truffle/DeployedAddresses.sol";
import "../contracts/MetaCoin.sol";

contract TestMetacoin {
  function testInitialBalanceUsingDeployedContract() {
    MetaCoin meta = MetaCoin(DeployedAddresses.MetaCoin());

    uint expected = 10000;

    Assert.equal(meta.getBalance(tx.origin), expected, "Owner should have 10000 MetaCoin initially");
  }

  function testInitialBalanceWithNewMetaCoin() {
    MetaCoin meta = new MetaCoin();

    uint expected = 10000;

    Assert.equal(meta.getBalance(tx.origin), expected, "Owner should have 10000 MetaCoin initially");
  }
}

And when running the test:

$ truffle test
Compiling ConvertLib.sol...
Compiling MetaCoin.sol...
Compiling ../test/TestMetacoin.sol...

  TestMetacoin
    ✓ testInitialBalanceUsingDeployedContract (61ms)
    ✓ testInitialBalanceWithNewMetaCoin (69ms)

  2 passing (3s)