giljr

Controller Output	Expectation Type	Result
Array of hashes	Array of strings	❌ Fail (structural mismatch)
Array of strings	Array of strings	✅ Pass (matches your current code)

giljr

Form	Example	When to Use
New (symbol)	{ status: 'ok' }	✅ Rails default & preferred
Old (rocket)	{ 'status' => 'ok' }	When keys aren’t symbols (like strings or variables)

giljr

Controller Hash → JSON → RSpec Test

Step	Controller Code Example	JSON Output	RSpec Expectation json = JSON.parse(response.body) (*)json = JSON.parse(response.body, symbolize_names: true)
1. Symbol keys	render json: { status: :ok, code: 200 }	{'status':'ok','code':200}	expect(json['status']).to eq('ok')
2. String keys

giljr

Aspect	Benefit	Possible Drawback
Memory use	Fewer objects	None significant
Performance	Faster for literal-heavy code	Slower if code needs to mutate
Code safety	Prevents accidental mutation	Breaks mutation-based logic
Compatibility	Works fine in modern code	May break older gems
Predictability	Immutable by default	Surprising when global, invisible switch

giljr

Aspect	Effect
Performance	Slightly improved (fewer allocations).
Memory usage	Reduced.
Safety	More immutable code, fewer side effects.
Compatibility	Might break older gems or DSLs relying on mutable strings.
Rails core	Generally safe, but not guaranteed for all gems.

giljr

Situation	Recommended Action
Modern app with well-maintained gems	Safe to try globally (test in dev/test first).
Legacy code or older gems	Risky — better use the magic comment per file.
Gem development	Avoid setting it globally — you’ll affect consumers.
Rails itself	Rails 7+ core code is largely safe with frozen literals, but it doesn’t assume global freezing.

giljr

The Six Magic Tricks

Origin	Query (returns something)	Command (changes something)
Incoming	① ✅ Assert return value	② ✅ Assert public side effect
To Self	③ 🚫 Ignore	④ 🚫 Ignore
Outgoing	⑤ 🚫 Ignore	⑥ ✅ Mock expectation

giljr

The Six Magic Tricks

by Sandi Metz

Origin	Query (returns something)	Command (changes something)
Incoming	① ✅ Assert return value	② ✅ Assert public side effect
To Self	③ 🚫 Ignore	④ 🚫 Ignore
Outgoing	⑤ 🚫 Ignore	⑥ ✅ Mock expectation

giljr

Quality	Meaning
Thorough	Fully prove object behavior
Stable	Don’t break on refactors
Fast	Run quickly and often
Few	Only test what matters

giljr

Circus Performer	Software Developer
Risks falling mid-act	Risks breaking existing features
Trusts the net beneath	Trusts the test suite beneath
Performs with confidence	Deploys with confidence