How can you be confident that your code is well-tested? For me, the criteria are straightforward: you feel comfortable deploying it automatically to production on a Friday evening, and the release pipeline stays as green as an evergreen tree. In this talk, I'll share some approaches that I am following to hit both targets for Node.js apps (APIs BFFs, etc)

1. Testing:
Do More
With Less
Practical approach to test
Node.js web-apps, APIs, BFFs
Eugene Fidelin AdvancedJS Amsterdam, 7 Feb 2024

2. 2
Is your code well-tested?
Do you feel comfortable
deploying it automatically
to production on a Friday
evening?
Does your release pipeline
stay as green as an
evergreen tree?

3. Why? DORA metrics
Lead Time for Changes
The amount of time it takes a
commit to get into production
Change Failure Rate
The percentage of deployments
causing a failure in production
3
Deployment Frequency
How often a team successfully
releases to production
Time to restore service
How long it takes a team to recover
from a failure in production

4. Static
Unit tests
Integration
tests
End to end
tests
Price Confidence Speed
Very high High Low
Low - Medium Very good High
Low Average High
Extra low Low Very high
4
How? Testing trophy

5. Steps to approach testing
0 2 4
1
Step 0
Enable static linters
Step 2
Write unit tests for
reusable parts and code
without coverage
Step 4
Use metrics to identify
anomalies on production
3
Step 3
Write very few e2e
tests only for the most
business critical flow(s)
Step 1
Create integration
tests for all happy and
non-happy flows

6. Unit tests
6
App code
Code to test
External lib/service
Test coverage
Mocks

7. Integration tests I
7
App code
Code to test
External lib/service
Test coverage
Mocks

8. Integration tests II
8
App code
Code to test
External lib/service
Test coverage
Mocks

9. Integration tests III
9
App code
Code to test
External lib/service
Test coverage
Mocks

10. End to end tests
10
App code
Code to test
External lib/service
Test coverage
Mocks

11. Key takeaways
11
Adopt Testing Trophy
01
Start with Integration tests
02
Reduce amount of
e2e test
03
Measure impact with
DORA metrics
04

12. Tools
node-mocks-http
Mock Express.js
request/response objects
superagent
Simulate incoming
request
Jest
Test framework, mock
deps, snapshots
nock
Mock downstream API
calls
12
Cypress.io
Testing in browser

13. CREDITS: This presentation template was
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Thanks!
13
Eugene Fidelin
Engineering Manager @
eugene.fidelin@gmail.com
linkedin.com/in/eugef
medium.com/@EugeneFidelin