feat: charges integration test

[turip]

Overview

The mock ledger is a bad ledger implementation.

The testcase contains // LEDGER[galexi]: comments where it is described what happens and which callbacks are invoked.

Notes for reviewer

Summary by CodeRabbit

Release Notes

• Tests
  • Added comprehensive test suite for credit and billing system functionality, including mock ledger implementation and end-to-end charge creation scenarios.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds test infrastructure for credits functionality, introducing a MockLedger implementation that tracks customer credits, promotional credits, invoice accruals, and receivables across multiple handler interfaces, along with a comprehensive sanity test suite validating end-to-end credit purchase and flat-fee charge workflows.

Changes

Cohort / File(s)	Summary
Credits Mock Handler test/credits/mockledger.go	Implements MockLedger with in-memory tracking of credit balances and interface implementations for flatfee.Handler, creditpurchase.Handler, and usagebased.Handler, providing methods for credit allocation, payment settlement, and balance management.
Credits Integration Tests test/credits/sanity_test.go	Comprehensive test suite bootstrapping billing/charge services with the MockLedger, including a scenario validating promotional and purchased credit realizations in flat-fee charges, with helper methods for charge intent creation, fetching, and validation.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• chore: split chages testcases #3960: Modifies charges test scaffolding and adds/alters test helper utilities for mock handlers and charge intent creation.

Suggested reviewers

• GAlexIHU

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'feat: charges integration test' directly and concisely describes the main addition: a new integration test suite for the charges system. It matches the PR's core objective of adding TestCreditsTestSuite and TestFlatFeePartialCreditRealizations.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/charges-integartion-tests

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[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (3)

test/credits/mockledger.go (1)

24-30: Consider using alpacadecimal.Decimal instead of float64 for monetary tracking.

Using float64 for monetary values (customerCredits, customerPromotionalCredits, invoiceAccruals, receivables) can introduce precision issues over time. While this is test code, using Decimal would better mirror production behavior and catch precision-related bugs.

That said, for a mock ledger in tests, this might be acceptable if you're okay with the trade-off.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@test/credits/mockledger.go` around lines 24 - 30, Replace the MockLedger's
float64 money fields with alpacadecimal.Decimal to avoid precision issues:
change customerCredits, customerPromotionalCredits, invoiceAccruals, and
receivables from float64 to alpacadecimal.Decimal in the MockLedger struct,
update any initialization/assignments and arithmetic in methods that use these
fields (e.g., constructors, Add/Charge/Balance helpers) to use Decimal
creation/operations, and import the alpacadecimal package so tests mirror
production behavior while keeping tests consistent.

test/credits/sanity_test.go (2)

404-422: Validation method should be on value receiver for consistency.

createCreditPurchaseIntentInput.Validate() (line 502) uses value receiver, but createMockChargeIntentInput.Validate() uses pointer receiver. For consistency (and since neither mutates state), consider using value receivers for both.

Proposed change

-func (i *createMockChargeIntentInput) Validate() error {
+func (i createMockChargeIntentInput) Validate() error {

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@test/credits/sanity_test.go` around lines 404 - 422, The Validate method for
createMockChargeIntentInput uses a pointer receiver but should use a value
receiver for consistency with createCreditPurchaseIntentInput.Validate and
because it does not mutate state; change the method signature from func (i
*createMockChargeIntentInput) Validate() error to use a value receiver (func (i
createMockChargeIntentInput) Validate() error) and keep the validation logic the
same, ensuring any references/calls still compile after changing the receiver.

---

339-343: Make credit realization assertions more explicit about credit types.

The test currently relies on array indices to identify credit types—CreditRealizations[0] for promotional and [1] for customer. While the order is intentional (the handler appends promotional credits first, then customer), the test would be clearer and less fragile by asserting on the credit type directly rather than relying on position:

for _, realization := range updatedFlatFeeCharge.State.CreditRealizations {
    if realization.Type == "promotional" {
        s.Equal(float64(30), realization.Amount.InexactFloat64())
    } else if realization.Type == "customer" {
        s.Equal(float64(50), realization.Amount.InexactFloat64())
    }
}

This makes the test's intent clearer and less dependent on handler implementation details.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@test/credits/sanity_test.go` around lines 339 - 343, The current assertions
index into updatedFlatFeeCharge.State.CreditRealizations which makes the test
fragile; change the test to iterate the CreditRealizations slice
(updatedFlatFeeCharge.State.CreditRealizations) and assert amounts based on
realization.Type (e.g., "promotional" -> 30, "customer" -> 50) so each
realization is checked by its Type rather than by position; update the
assertions in the test function where promotionalCreditRealization and
customerCreditRealization are read to use a loop and conditional checks on
realization.Type.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@test/credits/mockledger.go`:
- Around line 142-145: The Reset() on MockLedger currently only zeroes
customerCredits and customerPromotionalCredits but leaves invoiceAccruals and
receivables populated; update MockLedger.Reset to also clear invoiceAccruals and
receivables by reinitializing them to their zero/empty values (e.g., set maps to
nil or make(empty maps) or set slices to nil/empty slices) so no stale data
remains between tests; locate the Reset method on MockLedger and add assignments
that reset invoiceAccruals and receivables alongside customerCredits and
customerPromotionalCredits.
- Around line 57-70: The block can append a zero-amount credit when
totalToAllocate>0 but l.customerCredits==0; update the logic in the loop
handling totalToAllocate and l.customerCredits so you only create a
creditrealization.CreateInput when creditsToAllocate > 0 (i.e., compute
creditsToAllocate := math.Min(totalToAllocate, l.customerCredits) and if
creditsToAllocate <= 0 skip appending), ensure Amount uses
alpacadecimal.NewFromFloat(creditsToAllocate) only for positive values, and
resume correctly adjusting l.customerCredits (and totalToAllocate if that
variable is intended to be decremented) to avoid emitting invalid zero-amount
inputs.

---

Nitpick comments:
In `@test/credits/mockledger.go`:
- Around line 24-30: Replace the MockLedger's float64 money fields with
alpacadecimal.Decimal to avoid precision issues: change customerCredits,
customerPromotionalCredits, invoiceAccruals, and receivables from float64 to
alpacadecimal.Decimal in the MockLedger struct, update any
initialization/assignments and arithmetic in methods that use these fields
(e.g., constructors, Add/Charge/Balance helpers) to use Decimal
creation/operations, and import the alpacadecimal package so tests mirror
production behavior while keeping tests consistent.

In `@test/credits/sanity_test.go`:
- Around line 404-422: The Validate method for createMockChargeIntentInput uses
a pointer receiver but should use a value receiver for consistency with
createCreditPurchaseIntentInput.Validate and because it does not mutate state;
change the method signature from func (i *createMockChargeIntentInput)
Validate() error to use a value receiver (func (i createMockChargeIntentInput)
Validate() error) and keep the validation logic the same, ensuring any
references/calls still compile after changing the receiver.
- Around line 339-343: The current assertions index into
updatedFlatFeeCharge.State.CreditRealizations which makes the test fragile;
change the test to iterate the CreditRealizations slice
(updatedFlatFeeCharge.State.CreditRealizations) and assert amounts based on
realization.Type (e.g., "promotional" -> 30, "customer" -> 50) so each
realization is checked by its Type rather than by position; update the
assertions in the test function where promotionalCreditRealization and
customerCreditRealization are read to use a loop and conditional checks on
realization.Type.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 402ce9ef-d808-4f46-9957-9f5a13acab41

📥 Commits

Reviewing files that changed from the base of the PR and between 06bf23d and 1bdca94.

📒 Files selected for processing (2)

• test/credits/mockledger.go
• test/credits/sanity_test.go