diff --git a/__tests__/utils/randomNumbers.test.js b/__tests__/utils/randomNumbers.test.js
new file mode 100644
index 0000000..f8d7656
--- /dev/null
+++ b/__tests__/utils/randomNumbers.test.js
@@ -0,0 +1,65 @@
+import { getRandomNumbersFactory } from 'utils/randomNumbers'
+
+describe('getRandomNumbersFactory', () => {
+  test('should return a numbers factory', () => {
+    const getNumbers = getRandomNumbersFactory()
+    expect(typeof getNumbers).toBe('function')
+  })
+
+  test('should return an array of one number', () => {
+    const getNumbers = getRandomNumbersFactory()
+    const numbers = getNumbers()
+    expect(Array.isArray(numbers)).toBe(true)
+  })
+
+  test('should return a single random number', () => {
+    const getNumbers = getRandomNumbersFactory()
+    const numbers = getNumbers()
+    expect(numbers.length).toBe(1)
+    expect(numbers[0]).toBeGreaterThanOrEqual(0)
+    expect(numbers[0]).toBeLessThanOrEqual(1000)
+  })
+
+  test('should return array with exact length', () => {
+    const getNumbers = getRandomNumbersFactory(10, 10)
+    const numbers = getNumbers()
+    expect(numbers).toHaveLength(10)
+  })
+
+  test('should return array of different numbers', () => {
+    const getNumbers = getRandomNumbersFactory(100, 100)
+    const numbers = getNumbers()
+    const withoutRepeated = numbers.reduce(
+      (acc, number) => acc.includes(number) ? acc : acc.concat(number),
+      []
+    )
+    expect(numbers.length).toBeGreaterThanOrEqual(withoutRepeated.length)
+  })
+
+  test('should return numbers between bounds', () => {
+    const getNumbers = getRandomNumbersFactory(1000, 1000, [[10, 100]])
+    const numbers = getNumbers()
+    expect(numbers.filter(number => number < 10 || number > 100)).toHaveLength(0)
+  })
+
+  test('should return numbers between several bounds', () => {
+    const getNumbers = getRandomNumbersFactory(1000, 1000, [[10, 10], [100, 100]])
+    const numbers = getNumbers()
+    expect(numbers.includes(10)).toBe(true)
+    expect(numbers.includes(100)).toBe(true)
+  })
+
+  test('should return different numbers each time', () => {
+    const getNumbers = getRandomNumbersFactory(1, 1, [[1, 1000]])
+    const numbers1 = getNumbers()
+    const numbers2 = getNumbers()
+    expect(numbers1[0]).not.toBe(numbers2[0])
+  })
+
+  test('should return arrays with different length each time', () => {
+    const getNumbers = getRandomNumbersFactory(1, 1000, [[10, 100]])
+    const numbers1 = getNumbers()
+    const numbers2 = getNumbers()
+    expect(numbers1.length).not.toBe(numbers2.length)
+  })
+})
diff --git a/__tests__/utils/twoDigits.test.js b/__tests__/utils/twoDigits.test.js
new file mode 100644
index 0000000..81a4864
--- /dev/null
+++ b/__tests__/utils/twoDigits.test.js
@@ -0,0 +1,15 @@
+import { twoDigits } from 'utils/twoDigits'
+
+describe('twoDigits', () => {
+  test('should return same number as string', () => {
+    expect(twoDigits(10)).toBe('10')
+  })
+
+  test('should return number with left 0', () => {
+    expect(twoDigits(5)).toBe('05')
+  })
+
+  test('should return last two digits', () => {
+    expect(twoDigits(123)).toBe('23')
+  })
+})