This document discusses test-driven development (TDD) katas in Magento 2. It introduces the concept of code katas as a way to practice and train skills like athletes do. Specific skills trained in TDD Magento katas include the red-green-refactor process, working with test doubles, separating concerns, and testing Magento development. An example kata is provided to implement a custom "GiftItem" total model that sets prices of free gift items to zero and adjusts the subtotal. The goal is to help developers start practicing TDD with Magento through examples.

1. TDD Katas in Magento 2
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3. Code Kata
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4. Code Kata?
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5. We practice our craft.
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6. We train like
athletes do.
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7. What do we train in a code kata?
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8. The Mind
→ The 3 phases of TDD
→ Working in small units
→ Recognizing patterns
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9. The Body
→ Keyboard shortcuts
→ Efficient grouping of actions
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10. Framework Knowledge
→ Memorizing framework sections
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11. Katas are usually done
multiple times
over a
period of time.
E.g. once per day over 1 week,
once per week over 3 months,
...
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12. Time Limit:
15 - 30 minutes
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13. Today is just a
Demo
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14. An impression how
TDD in Magento
can look.
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15. To inspire you to
start doing katas
as soon as you are back!
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16. Today's Kata:
Magento 2 Total Model
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17. Total Models
A flexible system to calculate cart and cart
item prices and adjustments.
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18. <!-- File: etc/sales.xml -->
<section name="quote">
<group name="totals">
<item name="subtotal" sort_order="100"
instance="MagentoQuoteModelQuoteAddressTotalSubtotal"/>
<item name="tax_subtotal" sort_order="200"
instance="MagentoTaxModelSalesTotalQuoteSubtotal"/>
<item name="shipping" sort_order="250"
instance="MagentoQuoteModelQuoteAddressTotalShipping"/>
<item name="discount" sort_order="400"
instance="MagentoSalesRuleModelQuoteDiscount"/>
<item name="tax" sort_order="450"
instance="MagentoTaxModelSalesTotalQuoteTax"/>
<item name="grand_total" sort_order="550"
instance="MagentoQuoteModelQuoteAddressTotalGrand" />
</group>
</section>
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19. Processed in order
→ First comes subtotal
Sets quote item prices & subtotal
→ Then all the others
shipping, discount, tax, ...
→ Last comes grand_total
Sums up all other total models
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20. Each one adds it's value on
ModelQuoteAddressTotal
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21. The Kata Example code is
missing a custom total model.
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22. Training Module: Example_GiftItem
When a customer adds a product from the
sample data "Bags" attribute set,
to the cart, also add a free water bottle.
https://github.com/Vinai/module-example-giftitem
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23. Training Module: Example_GiftItem
The GiftItem total model is responsible
for setting the price of gift items to zero
and adjusting the subtotal.
https://github.com/Vinai/module-example-giftitem
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24. What does this kata teach?
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25. (1/2) Generic skills:
→ TDD Red-Green-Refactor process
→ Working with test doubles
→ Separating pure functions
from functions with side effects
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26. (2/2) Magento skills:
→ Test driving Magento development
→ The totals architecture
→ Dealing with Law of Demeter violations
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27. Tomorrow
How you can get started:
# Create module dir
mkdir -p app/code/Example && cd app/code/Example
# Clone repo
git clone https://github.com/Vinai/module-example-giftitem.git GiftItem
cd GiftItem
# Check out git tag
git checkout beginning-of-kata
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28. Kata Task:
Use TDD to create the GiftItem total model
ModelTotalsGiftItemAddressTotal
Implement the collect() method.
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29. Target behavior: collect()
→ Subtract gift item row totals sum and
base row totals sum from the subtotal
→ Set calculation_price
and base_calculation_price
of every gift item to zero
→ Call calcRowTotal on each gift
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30. Enjoy the session and
feel those reflexes
get sharper!
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