Add combinatorial tests for internal Exchange functions (#807)

* WIP add combinatorial tests for internal Exchange functions

* Change combinitorial testing strategy based on feedback

* Check value of filled[orderHash] in updateFilledState tests

* Add combinatorial tests for addFillResults

* Add combinatorial tests for getPartialAmount

* Implement generic `testWithReferenceFuncAsync`

* Implement generic `testCombinatoriallyWithReferenceFuncAsync`

* Add combinatorial tests for isRoundingError

* Add combinatorial tests for calculateFillResults

* Add support for Geth in internal contract tests

* Fix contract artifacts

* Change DECIMAL_PLACES to 78 and add a note.

* Document new functions in utils

* Optimize tests by only reseting state when needed

* Rename/move some files

* Print parameter names on failure in testWithReferenceFuncAsync

* Add to changelog for utils package

* Appease various linters

* Rename some more things related to FillOrderCombinatorialUtils

* Remove .only from test/exchange/internal.ts

* Remove old test for isRoundingError and getPartialAmount

* Appease linters again

* Remove old todos

* Fix typos, add comments, rename some things

* Re-add some LibMath tests

* Update contract internal tests to use new SafeMath revert reasons

* Apply PR feedback from Amir

* Apply PR feedback from Remco

* Re-add networks to ZRXToken artifact

* Remove duplicate Whitelist in compiler.json

2 files changed, 16 insertions, 2 deletions

diff --git a/packages/utils/CHANGELOG.json b/packages/utils/CHANGELOG.json
index c5f82d73b..8abfbaf43 100644
--- a/packages/utils/CHANGELOG.json
+++ b/packages/utils/CHANGELOG.json
@@ -1,5 +1,14 @@
 [
     {
+        "version": "1.0.5",
+        "changes": [
+            {
+                "note": "Increased BigNumber decimal precision from 20 to 78",
+                "pr": 807
+            }
+        ]
+    },
+    {
         "timestamp": 1532619515,
         "version": "1.0.4",
         "changes": [
diff --git a/packages/utils/src/configured_bignumber.ts b/packages/utils/src/configured_bignumber.ts
index e44c062c2..2b22b6938 100644
--- a/packages/utils/src/configured_bignumber.ts
+++ b/packages/utils/src/configured_bignumber.ts
@@ -1,9 +1,14 @@
 import { BigNumber } from 'bignumber.js';
 
-// By default BigNumber's `toString` method converts to exponential notation if the value has
-// more then 20 digits. We want to avoid this behavior, so we set EXPONENTIAL_AT to a high number
 BigNumber.config({
+    // By default BigNumber's `toString` method converts to exponential notation if the value has
+    // more then 20 digits. We want to avoid this behavior, so we set EXPONENTIAL_AT to a high number
     EXPONENTIAL_AT: 1000,
+    // Note(albrow): This is the lowest value for which
+    // `x.div(y).floor() === x.divToInt(y)`
+    // for all values of x and y <= MAX_UINT256, where MAX_UINT256 is the
+    // maximum number represented by the uint256 type in Solidity (2^256-1).
+    DECIMAL_PLACES: 78,
 });
 
 export { BigNumber };