Add math utils tests

apps/voting/app/src/math-utils.test.js

@@ -0,0 +1,73 @@
+import BN from 'bn.js'
+import { scaleBNValuesSet } from './math-utils'
+
+const scaleResults = (values, total, precision) =>
+  scaleBNValuesSet(values, new BN(total), precision).map(v => v.toString())
+
+describe('scaleBNValuesSet()', () => {
+  const sets = [
+    [
+      'should add round up the first number first',
+      [[0.5, 0.5], '329879'],
+      ['164940', '164939'],
+    ],
+    [
+      'should work with very big numbers',
+      [[0.5, 0.5], '3298792983798273972398792837972310987189327'],
+      [
+        '1649396491899136986199396418986155493594664',
+        '1649396491899136986199396418986155493594663',
+      ],
+    ],
+    [
+      'should return an empty array if an empty array is provided',
+      [[], '100'],
+      [],
+    ],
+    [
+      'should handle zero values',
+      [[0.9, 0, 0.1], '10000'],
+      ['9000', '0', '1000'],
+    ],
+    [
+      'should not correct the values if their sum is far enough from 1',
+      [[0.1, 0.1], '1000'],
+      ['100', '100'],
+    ],
+    [
+      'should correct the values if their sum is close enough to 1',
+      [[0.9, 0.099999], '1000'],
+      ['900', '100'],
+    ],
+    [
+      'should work with values that errored and made us debug this',
+      [[0.55, 0], '100'],
+      ['55', '0']
+    ]
+  ]
+
+  sets.forEach(([label, params, results]) => {
+    test(label, () => {
+      expect(scaleResults(...params)).toEqual(results)
+    })
+  })
+
+  test('should throw if the numbers are too far from 1', () => {
+    expect(() => {
+      scaleResults([1.1, 0.3], '1000')
+    }).toThrow(Error)
+    expect(() => {
+      scaleResults([2, 5], '1000')
+    }).toThrow(Error)
+  })
+
+  test('should adapt to the correction limit', () => {
+    expect(scaleResults([0.8, 0.1], '1000')).toEqual(['800', '100'])
+    expect(scaleResults([0.9, 0.1001], '1000')).toEqual(['900', '100'])
+    expect(scaleResults([0.8, 0.1], '1000', 0.1)).toEqual(['900', '100'])
+    expect(scaleResults([0.9, 0.099], '1000', 0)).toEqual(['900', '99'])
+    expect(() => {
+      scaleResults([0.9, 1.0001], '1000', 0)
+    }).toThrow(Error)
+  })
+})