# Contracts testing options

## Revert stack traces

If you want to see helpful stack traces (incl. line number, code snippet) for smart contract reverts, run the tests with:

```
yarn test:trace
```

**Note:** This currently slows down the test runs and is therefore not enabled by default.

## Backing Ethereum node

By default, our tests run against an in-process [Ganache](https://github.com/trufflesuite/ganache-core) instance. In order to run the tests against [Geth](https://github.com/ethereum/go-ethereum), first follow the instructions in the README for the devnet package to start the devnet Geth node. Then run:

```bash
TEST_PROVIDER=geth yarn test
```

## Code coverage

In order to see the Solidity code coverage output generated by `@0x/sol-coverage`, run:

```
yarn test:coverage
```

## Gas profiler

In order to profile the gas costs for a specific smart contract call/transaction, you can run the tests in `profiler` mode.

**Note:** Traces emitted by ganache have incorrect gas costs so we recommend using Geth for profiling.

```
TEST_PROVIDER=geth yarn test:profiler
```

You'll see a warning that you need to explicitly enable and disable the profiler before and after the block of code you want to profile.

```typescript
import { profiler } from './utils/profiler';
profiler.start();
// Some call to a smart contract
profiler.stop();
```

Without explicitly starting and stopping the profiler, the profiler output will be too busy, and therefore unusable.