Magento 2 Automated Testing via examples of Multi-Source Inventory (MSI)

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Automated Testing in
Magento 2
Igor Miniailo
Magento 2 Architect

*Automated Testing in Magento 2
based on examples from Multi-Source
Inventory

MSI is designed to enable stock management in multiple
locations so that merchants can properly reflect their physical
warehouses in Magento system without external extensions or
customization
Multi-Source Inventory (MSI)
https://github.com/magento-engcom/msi/

Split the inventory
between the
sources within one
Magento installation

Replace current CatalogInventory with MSI

Unit Testing

Unit test types
https://martinfowler.com/bliki/UnitTest.html

Test Doubles
https://martinfowler.com/bliki/TestDouble.html

Let’s see how typical Unit test for this code looks like

Solitary Unit Test with Mocks and Expects

TTDD - Tautological Test Driven Development
Tautological: - needless, redundant repetition of an idea - repetition of
same sense in different words; - the phrase "a beginner who has just
started" is tautological

TTDD - Tautological Test Driven Development
Unit tests currently do not check that code works
properly, but check that code works the same way
as we implemented it.
Coupling between Production and Testing code.
Test duplicates the business logic code.

http://fabiopereira.me/blog/2010/05/27/ttdd-tautological-
test-driven-development-anti-pattern/

• Asserts more interactions with collaborators than the outputs
• It doesn’t really test the behavior of the class, but only its
implementation
• The test is too white box
• Too much mock setup deviates the intent of the test
• Adding a new feature or changing an existing one requires
changing mock expectations
• Such tests don’t help to find bugs in application code

The problem is not in Unit tests
The problem is in Transient State of objects
under the test
(especially in legacy code)

Two Unit tests passed. No Integration tests

Whether Unit tests are useless?
NO!
Unit tests could be the first “Smell” informing that
something wrong with your application code

• Readability
– Test should be easy to follow
– Test should be simple to update
– Code can be reused to test all similar cases
• Stability
– Test should be stable by execution
– Test should be stable to code changes
– Test should focus on result not on the path
• Speed
Qualities of a Test

Integration Testing

Reservation - the entity is used when the order is placed and
we need to reserve some product quantity in stock.
Reservations are append only operations and help us to prevent
blocking operations and race conditions at the time of checkout.
Reservation mechanism
https://github.com/magento-engcom/msi/wiki/Reservations

Order Placement – Step 1
France Warehouse
SKU-1: 5qty
EU Stock
SKU-1: 15qty
Italy Warehouse
SKU-1: 10qty
Raw data Index Reservations
No records
Available Qty: 15qty (data from index, empty reservations)

Action: Customer buys 5 products on frontend

France Warehouse
SKU-1: 5qty
EU Stock
SKU-1: 15qty
Italy Warehouse
SKU-1: 10qty
SKU-1: -5
Available Qty: 10qty (data from index 15, apply all reservations -5)
Data is NOT changed Reservation has been
added

Action: Admin makes a re-order, 3 products out of 5 returned,
and new order consists of 2 products

France Warehouse
SKU-1: 5qty
EU Stock
SKU-1: 15qty
Italy Warehouse
SKU-1: 10qty
SKU-1: -5
SKU-1: +3
Available Qty: 13qty (data from index 15, apply reservations -5+3)
Data is NOT changed
Reservation has been added

Action: Admin completes order. Re-index was run.

France Warehouse
SKU-1: 3qty
EU Stock
SKU-1: 13qty
Italy Warehouse
SKU-1: 10qty
SKU-1: -5
SKU-1: +3
SKU-1: +2
Available Qty: 13qty (data from index 13, apply reservations -5+3+2=0)
Data is CHANGED Compensation Reservation
has been added

Action: Reservation cleaning
Looping through these reservations we could find reservations
which in sum gives 0 (Zero) and remove them.

Order Placement – Step 9 (like Step 1)
France Warehouse
SKU-1: 3qty
EU Stock
SKU-1: 13qty
Italy Warehouse
SKU-1: 10qty
Available Qty: 13qty (data from index, empty reservations)
Data is NOT changed Reservations have been removed
No records

API interface to test

So, what’s about testing?

What about fixtures?

Tests Isolation

Using DocBlock Annotations
http://devdocs.magento.com/guides/v2.2/test/integration/annotations.html

Clean the state after your tests!

Cleaning up the state. Rollback Fixtures

Cleaning up the state

• Readability
– Test should be easy to follow
– Test should be simple to update
– Code can be reused to test all similar cases
• Stability
– Test should be stable by execution
– Test should be stable to code changes
– Test should focus on result not on the path
• Speed
Qualities of a Test

Web API Testing

Headless Magento

RESTful API

Swagger
http://devdocs.magento.com/guides/v2.2/rest/generate-local.html

Web API tests
https://github.com/magento-engcom/msi/wiki/How-to-create-Web-API-and-How-To-cover-them-with-Functional-Testing

Database Generated IDs

Why can’t we just use predefined IDs?

Predefined ID approach (used in MSI)

Predefined IDs matter
Just for this particular case (Source to Stock assignment) - we got rid of more
than 300 lines of boilerplate code in our Integration tests using Pre-Generated
IDs approach.
https://github.com/magento-engcom/msi/wiki/The-first-step-towards-pre-generated-
IDs.-And-how-this-will-improve-your-Integration-tests

Be Responsible or train your dog tests to be!

Static Testing

Strict Typing

declare(strict_types=1)

LiveCodeTest

Functional Testing

http://devdocs.magento.com/guides/v2.2/mtf/mtf_introduction.html

How to join us? Send an email to
engcom@magento.com
@iminyaylo
Thank y’all!

Magento 2 Automated Testing via examples of Multi-Source Inventory (MSI)

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