From 8422633b8ab070d3321b7f9d557677773695e8aa Mon Sep 17 00:00:00 2001
From: Sonu Kapoor <sonukapoor@gmail.com>
Date: Sat, 19 Sep 2020 12:41:59 -0400
Subject: [PATCH] test(docs-infra): add missing unit tests for backoff example
 (#38896)

This commit adds the missing unit test for the backoff example.

PR Close #38896
---
 .../src/backoff.spec.ts                       | 70 +++++++++++++++++++
 .../practical-observable-usage/src/backoff.ts | 20 ++++--
 2 files changed, 84 insertions(+), 6 deletions(-)
 create mode 100644 aio/content/examples/practical-observable-usage/src/backoff.spec.ts

diff --git a/aio/content/examples/practical-observable-usage/src/backoff.spec.ts b/aio/content/examples/practical-observable-usage/src/backoff.spec.ts
new file mode 100644
index 0000000000..0390a476d1
--- /dev/null
+++ b/aio/content/examples/practical-observable-usage/src/backoff.spec.ts
@@ -0,0 +1,70 @@
+import { interval } from 'rxjs';
+import { tap } from 'rxjs/operators';
+import { backoff } from './backoff';
+
+describe('backoff()', () => {
+  beforeEach(() => jasmine.clock().install());
+  afterEach(() => jasmine.clock().uninstall());
+
+  it('should retry in case of error', () => {
+    const mockConsole = {log: jasmine.createSpy('log')};
+    const source = interval(10).pipe(
+      tap(i => {
+        if (i > 0) {
+          throw new Error('Test error');
+        }
+      }),
+      backoff(3, 100),
+    );
+    source.subscribe({
+      next: v => mockConsole.log(`Emitted: ${v}`),
+      error: e => mockConsole.log(`Errored: ${e.message || e}`),
+      complete: () => mockConsole.log('Completed'),
+    });
+
+    // Initial try:
+    // Errors on second emission and schedules retrying (with delay).
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Emitted: 0']]);
+
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Emitted: 0']]);
+    mockConsole.log.calls.reset();
+
+    // First re-attempt after 100ms:
+    // Errors again on second emission and schedules retrying (with larger delay).
+    jasmine.clock().tick(100);
+    expect(mockConsole.log).not.toHaveBeenCalled();
+
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Emitted: 0']]);
+
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Emitted: 0']]);
+    mockConsole.log.calls.reset();
+
+    // Second re-attempt after 400ms:
+    // Errors again on second emission and schedules retrying (with even larger delay).
+    jasmine.clock().tick(400);
+    expect(mockConsole.log).not.toHaveBeenCalled();
+
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Emitted: 0']]);
+
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Emitted: 0']]);
+    mockConsole.log.calls.reset();
+
+    // Third re-attempt after 900ms:
+    // Errors again on second emission and gives up (no retrying).
+    jasmine.clock().tick(900);
+    expect(mockConsole.log).not.toHaveBeenCalled();
+
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Emitted: 0']]);
+    mockConsole.log.calls.reset();
+
+    jasmine.clock().tick(10);
+    expect(mockConsole.log.calls.allArgs()).toEqual([['Errored: Test error']]);
+  });
+});
diff --git a/aio/content/examples/practical-observable-usage/src/backoff.ts b/aio/content/examples/practical-observable-usage/src/backoff.ts
index 677ed0b2a4..68d724d097 100644
--- a/aio/content/examples/practical-observable-usage/src/backoff.ts
+++ b/aio/content/examples/practical-observable-usage/src/backoff.ts
@@ -1,9 +1,10 @@
-// TODO: Add unit tests for this file.
+// #docplaster
+// #docregion
 import { of, pipe, range, throwError, timer, zip } from 'rxjs';
 import { ajax } from 'rxjs/ajax';
 import { map, mergeMap, retryWhen } from 'rxjs/operators';
 
-function backoff(maxTries, delay) {
+export function backoff(maxTries, delay) {
   return pipe(
     retryWhen(attempts =>
       zip(range(1, maxTries + 1), attempts).pipe(
@@ -15,10 +16,17 @@ function backoff(maxTries, delay) {
   );
 }
 
+// #enddocregion
+/*
+  This function declaration is necessary to ensure that it does not get called
+  when running the unit tests. It will not get rendered into the docs.
+  The indentation needs to start in the leftmost level position as well because of how
+  the docplaster combines the different regions together.
+*/
+function docRegionAjaxCall() {
+// #docregion
 ajax('/api/endpoint')
   .pipe(backoff(3, 250))
-  .subscribe(data => handleData(data));
-
-function handleData(data) {
-  // ...
+  .subscribe(function handleData(data) { /* ... */ });
+// #enddocregion
 }