Testing on Daffa Abhipraya

PPL: Mutation Testing, From Setup to Score [Sprint 2, Week 3]

Wed, 15 Apr 2026 00:00:00 +0700

What I Worked On

Two weeks on mutation testing across the SIRA codebase. The first week wired mutmut (Python) and Stryker (TypeScript) into the pipeline and uncovered the uncomfortable truth: 91% line coverage on the services layer translated to a mutation score just above zero in places. The second week closed that gap by writing 400+ targeted tests across two rounds, driving the API mutation score from ~66% to 80.3%. This blog tells the full arc.

PPL: When 91% Test Coverage Means Nothing

Thu, 09 Apr 2026 00:00:00 +0700

We had 91% line coverage and felt good about it. Then we ran mutation testing and scored 0%. Every line of our service layer was executed by tests, but almost nothing was actually verified. This is the story of how we discovered the gap between “code was run” and “code was checked,” and what we changed to close it.

Note: Our project is hosted on an internal GitLab instance, so we use the term MR (Merge Request) throughout this blog. If you’re coming from GitHub, MRs are the equivalent of Pull Requests (PRs).

PPL: TDD [Sprint 2, Week 2]

Mon, 30 Mar 2026 00:00:00 +0700

What I Worked On

Three new features landed this week that each required TDD from scratch: multi-device session management (SIRA-214), invoice cancellation (SIRA-125), and blocking inactive accounts (SIRA-215). All three followed the red-green cycle and included mock isolation for external dependencies.

Session Management: Testing Stateful Logic with Mocks

SIRA-214 (MR !120) introduced SessionService, which manages active sessions per user with a device limit. The service has non-trivial state: upsert if session already exists, kick oldest if at capacity, validate ownership before revoking.

PPL: Beyond Unit Tests [Sprint 2, Week 1]

Mon, 23 Mar 2026 00:00:00 +0700

What I Worked On

This week I pushed our testing strategy well beyond standard unit tests. The project already had 433 backend and 200 frontend tests with 91% line coverage, but I wanted to answer a harder question: do our tests actually catch bugs, or do they just execute code?

I added four advanced testing approaches: property-based testing (Hypothesis + fast-check), behavioral testing (pytest-bdd with Gherkin), mutation testing (mutmut + Stryker), and test isolation verification (pytest-randomly). The results were eye-opening.

PPL: When 91% Test Coverage Means Nothing

Sun, 15 Mar 2026 00:00:00 +0700

We had 91% line coverage and felt good about it. Then we ran mutation testing and scored 0%. Every line of our service layer was executed by tests; almost nothing was actually verified. This is the story of how six advanced testing tools exposed the gap between “code was run” and “code was checked,” and what that means for any team relying on coverage as a quality signal.

Note: Our project is hosted on an internal GitLab instance, so we use the term MR (Merge Request) throughout this blog. If you’re coming from GitHub, MRs are the equivalent of Pull Requests (PRs).

PPL: Test-Driven Development [Sprint 1, Week 3]

Fri, 13 Mar 2026 00:00:00 +0700

What I Worked On

This week shipped three full-stack features using strict TDD discipline: invoice management (CRUD + filtering), layout/dashboard (sidebar, header, dashboard with role-based navigation), and a payments sidebar navigation link. Each feature followed red-green-refactor with tagged commits.

The project now has 392 backend tests and 195 frontend tests (587 total), up from 51 last week.

Red-Green-Refactor Commit Discipline

Every feature branch this week followed tagged commits so the TDD flow is auditable from the git history alone.

PPL: Test-Driven Development in a FastAPI Project [Sprint 1, Week 2]

Wed, 04 Mar 2026 00:00:00 +0700

TDD forces you to think about the interface before the implementation. This post covers how it was applied in the Smart Invoice Reminder AI (SIRA) backend for Sprint 1.

Test Distribution

The API currently has 51 test functions across 4 files:

File	Tests	Scope
`tests/test_auth.py`	14	JWT validation, RBAC, DB queries
`tests/test_payments.py`	24	Payment CRUD, business logic, edge cases
`tests/test_db_schema_and_seed.py`	6	Migration integrity, seed validation
`tests/test_logging_middleware.py`	7	HTTP access logging, request/response capture

Red-Green-Refactor

The authentication feature (SIRA-26) followed strict TDD commit discipline. Each backend function got its own RED commit (failing test) followed by a GREEN commit (passing implementation) before any cleanup.

Testing on Daffa Abhipraya

PPL: Mutation Testing, From Setup to Score [Sprint 2, Week 3]

# What I Worked On

PPL: When 91% Test Coverage Means Nothing

PPL: TDD [Sprint 2, Week 2]

# What I Worked On

# Session Management: Testing Stateful Logic with Mocks

PPL: Beyond Unit Tests [Sprint 2, Week 1]

# What I Worked On

PPL: When 91% Test Coverage Means Nothing

PPL: Test-Driven Development [Sprint 1, Week 3]

# What I Worked On

# Red-Green-Refactor Commit Discipline

PPL: Test-Driven Development in a FastAPI Project [Sprint 1, Week 2]

# Test Distribution

# Red-Green-Refactor

What I Worked On

What I Worked On

Session Management: Testing Stateful Logic with Mocks

What I Worked On

What I Worked On

Red-Green-Refactor Commit Discipline

Test Distribution

Red-Green-Refactor