[IP-135]: add unit tests for InvoiceCalculator and QuoteCalculator

[nielsdrost7]

Closes #135

What was missing

No tests existed for InvoiceCalculator or QuoteCalculator — the core tax calculation logic had zero coverage.

Changes

Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php (8 tests, no DB required):

• it_calculates_subtotal_from_quantity_and_price
• it_applies_item_level_tax
• it_applies_two_tax_rates
• it_applies_item_discount_before_tax — verifies discount reduces the taxable base, not the display subtotal
• it_calculates_grand_total_with_taxes
• it_applies_document_level_discount
• it_applies_percentage_discount
• it_aggregates_multiple_items
• it_returns_zero_totals_for_empty_items

Modules/Quotes/Tests/Unit/QuoteCalculatorTest.php (7 tests, no DB required):

• it_calculates_subtotal_from_quantity_and_price
• it_applies_tax_rate_from_relationship_object — exercises the Eloquent object path (item as stdClass with ->taxRate property)
• it_applies_two_tax_rates_from_relationship_objects
• it_applies_percentage_discount_before_tax
• it_applies_document_level_percentage_discount — uses quote_discount_percent field name
• it_aggregates_totals_across_multiple_items
• it_returns_zero_totals_for_empty_item_list

Both test classes extend AbstractTestCase (no RefreshDatabase). They test the real, existing calculator logic — no mocking, all tests should pass immediately.

Run

php artisan test --filter="InvoiceCalculatorTest|QuoteCalculatorTest"

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Generated by Claude Code

Summary by CodeRabbit

• Tests
  • Added comprehensive test suite for invoice calculations, validating subtotal computation, tax rates, item-level and document-level discounts, edge cases, and floating-point precision across various scenarios
  • Added comprehensive test suite for quote calculations, covering subtotal computation, tax handling, percentage-based discounts, edge cases, and behavior with negative inputs

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📝 Walkthrough

Walkthrough

Two new PHPUnit test classes are added: InvoiceCalculatorTest (404 lines) and QuoteCalculatorTest (391 lines). Both cover calculateTotals() across subtotal computation, single/multiple tax rates, item- and document-level discounts, multi-item aggregation, edge cases, floating-point precision, and negative-input behavior.

Changes

InvoiceCalculator Unit Tests

Layer / File(s)	Summary
Test class setup and core calculation tests Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php	Defines InvoiceCalculatorTest extending AbstractTestCase with setUp(), and tests item subtotal computation, single/dual item tax rates, item discount reducing the taxable base before tax, and grand total with taxes.
Document-level discount and multi-item aggregation tests Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php	Asserts fixed-amount and percentage document-level discounts are correctly applied, and that subtotals and totals aggregate correctly across multiple line items.
Edge cases: zero values, clamping, and 100% discount Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php	Tests empty item list, zero quantity, zero unit price, zero tax rates, item-discount-exceeds-subtotal clamping (tax zeroed), and 100% document discount yielding a zero total while reporting the discount amount.
Single-item, multi-tax, precision, balance, and negative-input tests Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php	Tests single-item correctness, cross-item multi-rate tax summation, floating-point precision using deltas across many items, partial-payment balance computation, non-throwing negative quantity/price inputs producing negative results, and the mockDocument() helper.

QuoteCalculator Unit Tests

Layer / File(s)	Summary
Test class setup and core calculation tests Modules/Quotes/Tests/Unit/QuoteCalculatorTest.php	Defines QuoteCalculatorTest with setUp(), and tests item subtotals, single/dual relationship-object tax rates, item-level percentage discount applied before tax, document-level percentage discount, and multi-item aggregation.
Edge cases: zero values, clamping, and 100% discount Modules/Quotes/Tests/Unit/QuoteCalculatorTest.php	Tests zero quantity, zero unit price, zero tax rates (tax forced to 0, subtotal unaffected), tax-base clamping when item discount exceeds subtotal, and 100% document discount producing a zero total.
Single-item, multi-tax, precision, flat discount, and negative-input tests Modules/Quotes/Tests/Unit/QuoteCalculatorTest.php	Tests single-item correctness, cross-item multi-rate tax summation via relationship objects, floating-point precision, flat document discount affecting discount_amount and total, failing-path documentation comments, non-throwing negative quantity/price inputs, and the mockDocument() helper.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~15 minutes

Poem

🐇 Hippity-hop, the tests are here,
Subtotals, taxes — crystal clear!
Discounts clamp and zeros behave,
Floating points kept well-behaved.
From invoice to quote, the math rings true,
No exception thrown — we hop right through! 🧮

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 9.52% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Linked Issues check	✅ Passed	The PR implements comprehensive unit tests covering tax calculations with multiple tax rates, discounts, and edge cases as required by issue #135, demonstrating progress toward 100% test coverage objectives.
Out of Scope Changes check	✅ Passed	All changes are directly focused on adding unit test coverage for InvoiceCalculator and QuoteCalculator, with no unrelated modifications outside the stated testing objectives.
Title check	✅ Passed	The title accurately summarizes the main change: adding unit tests for InvoiceCalculator and QuoteCalculator.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/135-calculator-unit-tests

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[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (1)

Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php (1)

100-103: ⚡ Quick win

Strengthen this assertion to exact total math.

assertGreaterThan(200.00, $totals['total']) is too permissive for a deterministic case and can let incorrect totals pass. Assert the exact expected value (with delta) to protect regression detection.

Suggested change

-        $this->assertGreaterThan(200.00, $totals['total']);
+        $this->assertEqualsWithDelta(284.00, $totals['total'], 0.001);

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php` around lines 100 -
103, The assertion at the end of the test method uses assertGreaterThan to only
verify that the total is greater than 200.00, which is too lenient for a
deterministic calculation and allows incorrect totals to pass. Replace the
assertGreaterThan call with assertEquals to assert the exact expected grand
total value (200 + 42 + 42 = 284.00) using an appropriate delta parameter to
handle floating point precision, ensuring that regressions in the calculation
logic are properly detected.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php`:
- Around line 21-393: Add the #[Group(...)] attribute to each test method in the
InvoiceCalculatorTest class to comply with test organization guidelines. For
each test method (it_calculates_subtotal_from_quantity_and_price,
it_applies_item_level_tax, it_applies_two_tax_rates,
it_applies_item_discount_before_tax, it_calculates_grand_total_with_taxes,
it_applies_document_level_discount, it_applies_percentage_discount,
it_aggregates_multiple_items, it_returns_zero_totals_for_empty_items, and all
edge case and failing path tests), place the #[Group('...')] attribute on the
line immediately before the #[Test] attribute using an appropriate group label
such as 'invoice_calculation', 'edge_cases', or 'failing_path' to categorize the
test's purpose and scope.

In `@Modules/Quotes/Tests/Unit/QuoteCalculatorTest.php`:
- Around line 21-380: All test methods in the QuoteCalculatorTest.php file are
missing the required `#[Group(...)]` attribute per repository standards. Add a
`#[Group(...)]` attribute directly before each `#[Test]` attribute for all test
methods (it_calculates_subtotal_from_quantity_and_price,
it_applies_tax_rate_from_relationship_object,
it_applies_two_tax_rates_from_relationship_objects,
it_applies_percentage_discount_before_tax,
it_applies_document_level_percentage_discount,
it_aggregates_totals_across_multiple_items,
it_returns_zero_totals_for_empty_item_list,
it_returns_zero_total_when_item_quantity_is_zero,
it_returns_zero_total_when_unit_price_is_zero,
it_returns_zero_tax_total_when_tax_rate_is_zero,
it_clamps_tax_base_to_zero_when_item_discount_exceeds_subtotal,
it_applies_100_percent_document_discount_resulting_in_zero_total,
it_handles_single_item_correctly,
it_sums_taxes_from_multiple_items_with_relationship_objects,
it_handles_floating_point_precision_across_multiple_items,
it_applies_flat_document_discount,
it_produces_negative_subtotal_for_negative_quantity_without_throwing, and
it_produces_negative_subtotal_for_negative_price_without_throwing). Select an
appropriate group annotation based on each test's intent, such as 'crud' for
core business logic tests.

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Nitpick comments:
In `@Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php`:
- Around line 100-103: The assertion at the end of the test method uses
assertGreaterThan to only verify that the total is greater than 200.00, which is
too lenient for a deterministic calculation and allows incorrect totals to pass.
Replace the assertGreaterThan call with assertEquals to assert the exact
expected grand total value (200 + 42 + 42 = 284.00) using an appropriate delta
parameter to handle floating point precision, ensuring that regressions in the
calculation logic are properly detected.

🪄 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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📥 Commits

Reviewing files that changed from the base of the PR and between e78f2ae and 2b22da9.

📒 Files selected for processing (2)

• Modules/Invoices/Tests/Unit/InvoiceCalculatorTest.php
• Modules/Quotes/Tests/Unit/QuoteCalculatorTest.php