revert "Proposal for balance redesign (#13)" (was a breaking change)

This reverts commit b0fe51b.

Author: frangio

Diff for: README.md

@@ -49,36 +49,16 @@ All returned numbers are of type [BN](https://github.com/indutny/bn.js).
 ---
 
 ### balance
-Helper to keep track of ether balances of a specific account
-
-#### balance current
-##### async balance.current(account)
-Returns the current balance of an account
-```javascript
-const balance = await balance.current(account)
-```
-
-#### balance tracker
-##### async balance.get
+#### async balance.current (account)
 Returns the current Ether balance of an account.
-```javascript
-const balanceTracker = await balance.tracker(account) //instantiation
-const accounBalance = await balanceTracker.get() //returns the current balance of account
-```
-##### async balance.delta
-Returns the change in the Ether since the last check(either `get()` or `delta()`)
+
+#### async balance.difference (account, promiseFunc)
+Returns the change in the Ether balance of an account caused by executing `promiseFunc` (which will be awaited on).
 
 ```javascript
-const balanceTracker = await balance.tracker(receiver)
-send.ether(sender, receiver, ether('10'))
-(await balanceTracker.delta()).should.be.bignumber.equal('10');
-(await balanceTracker.delta()).should.be.bignumber.equal('0');
-```
-Or using `get()`:
-```javascript
-const balanceTracker = await balance.tracker(account) //instantiation
-const accounBalance = await balanceTracker.get() //returns the current balance of account
-(await balanceTracker.delta()).should.be.bignumber.equal('0');
+(await balance.difference(receiver, () =>
+  send.ether(sender, receiver, ether('1')))
+).should.be.bignumber.equal(ether('1'));
 ```
 
 ---

Diff for: src/balance.js

@@ -1,32 +1,17 @@
 const { BN } = require('./setup');
 
-class Tracker {
-  constructor (acc) {
-    this.account = acc;
-  }
-  async delta () {
-    const current = await balanceCurrent(this.account);
-    const delta = current.sub(this.prev);
-    this.prev = current;
-    return delta;
-  }
-  async get () {
-    this.prev = await balanceCurrent(this.account);
-    return this.prev;
-  }
-}
-
-async function balanceTracker (owner) {
-  const tracker = new Tracker(owner);
-  await tracker.get();
-  return tracker;
-}
-
 async function balanceCurrent (account) {
   return new BN(await web3.eth.getBalance(account));
 }
 
+async function balanceDifference (account, promiseFunc) {
+  const balanceBefore = new BN(await web3.eth.getBalance(account));
+  await promiseFunc();
+  const balanceAfter = new BN(await web3.eth.getBalance(account));
+  return balanceAfter.sub(balanceBefore);
+}
+
 module.exports = {
   current: balanceCurrent,
-  tracker: balanceTracker,
+  difference: balanceDifference,
 };

Diff for: test-integration/simple-project-truffle-5.x/test/accounts.test.js

@@ -3,8 +3,9 @@ const { balance, BN, ether, send } = require('openzeppelin-test-helpers');
 contract('accounts', function (accounts) {
   it('sends ether and tracks balances', async function () {
     const value = ether('42', 'ether');
-    const tracker = await balance.tracker(accounts[0]);
-    await send.ether(accounts[0], accounts[1], value);
-    (await tracker.delta()).should.be.bignumber.equals(value.neg());
+
+    (await balance.difference(accounts[0], () =>
+      send.ether(accounts[0], accounts[1], value)
+    )).should.be.bignumber.equals(value.neg());
   });
 });

Diff for: test/src/balance.test.js

@@ -11,44 +11,17 @@ contract('balance', function ([sender, receiver]) {
     });
   });
 
-  describe('balance tracker', function () {
-    it('returns current balance ', async function () {
-      const tracker = await balance.tracker(receiver);
-      (await tracker.get()).should.be.bignumber.equal(await web3.eth.getBalance(receiver));
-    });
-
-    it('get() adds a new checkpoint ', async function () {
-      const tracker = await balance.tracker(sender);
-      await send.ether(sender, receiver, ether('1'));
-      await tracker.get();
-      (await tracker.delta()).should.be.bignumber.equal('0');
-    });
-
-    it('returns correct deltas after get() checkpoint', async function () {
-      const tracker = await balance.tracker(receiver);
-      await send.ether(sender, receiver, ether('1'));
-      await tracker.get();
-      await send.ether(sender, receiver, ether('1'));
-      (await tracker.delta()).should.be.bignumber.equal(ether('1'));
-    });
-
+  describe('difference', function () {
     it('returns balance increments', async function () {
-      const tracker = await balance.tracker(receiver);
-      await send.ether(sender, receiver, ether('1'));
-      (await tracker.delta()).should.be.bignumber.equal(ether('1'));
+      (await balance.difference(receiver, () =>
+        send.ether(sender, receiver, ether('1')))
+      ).should.be.bignumber.equal(ether('1'));
     });
 
     it('returns balance decrements', async function () {
-      const tracker = await balance.tracker(sender);
-      await send.ether(sender, receiver, ether('1'));
-      (await tracker.delta()).should.be.bignumber.equal(ether('-1'));
-    });
-
-    it('returns consecutive deltas', async function () {
-      const tracker = await balance.tracker(sender);
-      await send.ether(sender, receiver, ether('1'));
-      await tracker.delta();
-      (await tracker.delta()).should.be.bignumber.equal('0');
+      (await balance.difference(sender, () =>
+        send.ether(sender, receiver, ether('1')))
+      ).should.be.bignumber.equal(ether('-1'));
     });
   });
 });