feat: add unit tests for collection utils (#2564)

Closes #2406

packages/xrpl/src/utils/collections.ts

@@ -14,20 +14,24 @@ type ValueOf<T> = T[keyof T]
  */
 export function groupBy<T>(
   array: T[],
-  iteratee: (value: T, index: number, array: T[]) => string,
-): { [p: string]: T[] } {
+  iteratee: (value: T, index: number, array: T[]) => string | number,
+): Record<string | number, T[]> {
   // eslint-disable-next-line max-params -- need all the params for the fallback
-  return array.reduce<{ [key: string]: T[] }>(function predicate(
-    acc,
-    value,
-    index,
-    arrayReference,
-  ) {
-    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- being safe for js users
-    ;(acc[iteratee(value, index, arrayReference)] ||= []).push(value)
+  function predicate(
+    acc: Record<string | number, T[]>,
+    value: T,
+    index: number,
+    arrayReference: T[],
+  ): Record<string | number, T[]> {
+    const key = iteratee(value, index, arrayReference) || 0
+    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- Find existing group or create a new one
+    const group = acc[key] || []
+    group.push(value)
+    acc[key] = group
     return acc
-  },
-  {})
+  }
+
+  return array.reduce(predicate, {})
 }
 
 /**

packages/xrpl/test/utils/collections.test.ts

@@ -0,0 +1,27 @@
+import { groupBy, omitBy } from '../../src/utils/collections'
+
+describe('Collection Utils:', () => {
+  // Inspired from tests at https://github.com/lodash/lodash/blob/main/test/groupBy.spec.js
+  describe('groupBy', () => {
+    const array = [6.1, 4.2, 6.3]
+
+    it('should transform keys by `iteratee`', () => {
+      const actual = groupBy(array, Math.floor)
+      expect(actual).toEqual({ 4: [4.2], 6: [6.1, 6.3] })
+    })
+
+    it('should transform keys by `iteratee` that returns strings', () => {
+      const actual = groupBy(array, (item) => Math.floor(item).toString())
+      expect(actual).toEqual({ '4': [4.2], '6': [6.1, 6.3] })
+    })
+  })
+
+  // Taken from https://github.com/lodash/lodash/blob/main/test/omitBy.spec.js
+  describe('omitBy', () => {
+    it('should work with a predicate argument', () => {
+      const object = { aa: 1, bb: 2, cc: 3, dd: 4 }
+      const actual = omitBy(object, (num) => num !== 2 && num !== 4)
+      expect(actual).toEqual({ bb: 2, dd: 4 })
+    })
+  })
+})