From 4ada9137e161c99b82494a3388a8e002d895b19e Mon Sep 17 00:00:00 2001
From: Vadim <korobeinikovv@mail.ru>
Date: Sat, 3 Jul 2021 23:29:37 +0300
Subject: [PATCH] #31 : Add unit tests

---
 src/utils/interval.test.js | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 src/utils/interval.test.js

diff --git a/src/utils/interval.test.js b/src/utils/interval.test.js
new file mode 100644
index 0000000..9aa209f
--- /dev/null
+++ b/src/utils/interval.test.js
@@ -0,0 +1,30 @@
+import {
+  setIntervalImmediate,
+} from './interval.js'
+
+describe('setIntervalImmediate', () => {
+  beforeEach(() => {
+    jest.useFakeTimers();
+  })
+
+  it('runs callback immediately and them each n ms', () => {
+    let interval
+    const durationMs = 1000
+
+    const callNumbersToStopTimer = 3
+    let calledTimes = 0
+    const callback = () => {
+      calledTimes++
+      if (calledTimes === callNumbersToStopTimer) {
+        clearInterval(interval)
+      }
+    }
+
+    interval = setIntervalImmediate(callback, durationMs)
+    jest.runAllTimers()
+
+    expect(calledTimes).toBe(callNumbersToStopTimer)
+    expect(setInterval).toHaveBeenCalledWith(expect.any(Function), durationMs)
+    expect(clearInterval).toHaveBeenCalledWith(interval)
+  })
+})