Merge branch 'v2-prototype' into feature/combinatorial-testing

* v2-prototype: (21 commits)
  Don't use variables for revert reasons
  Add comments to dispatchTransferFrom
  Document IAssetData
  Compute bytes4 proxyid constants
  Return inplace bytes in LibBytes.readBytesWithLength
  Add Greg's documentation to MixinErc721Transfer
  Add Greg's documentation to MixinErc20Transfer
  Gas golf the transfer success logic
  Optimize like in PR #767
  Run prettier and fix linting errors
  Fix tests
  Update tests
  Fix AssetProxyUtils
  Update tests
  Fix ERC721Proxy TokenId
  Update AssetProxyUtils
  Add IAssetData
  WIP
  ABI encoded asset data
  Remove proxyId argument from dispatchTransferFrom
  ...

# Conflicts:
#	packages/contracts/test/asset_proxy/proxies.ts

1 files changed, 43 insertions, 3 deletions

diff --git a/packages/contracts/README.md b/packages/contracts/README.md
index 9c829c753..2e6376f39 100644
--- a/packages/contracts/README.md
+++ b/packages/contracts/README.md
@@ -64,11 +64,51 @@ yarn lint
 yarn test
 ```
 
-### Run Tests Against Geth
+#### Testing options
 
-Follow the instructions in the README for the devnet package to start the
-devnet.
+###### 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 `@0xproject/sol-cov`, 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.