mitgliederverwaltung/docs/test-slow-suite.md

# Slow Test Suite Documentation

**Date:** 2026-01-28  
**Status:** ✅ Active

---

## Overview

The Slow Test Suite contains performance tests that explicitly validate performance characteristics of the application. These tests are intentionally slower because they use larger datasets or test performance-critical paths (e.g., N+1 query prevention, filter performance with many records).

These tests are marked with `@tag :slow` or `@moduletag :slow` and are excluded from standard test runs to improve developer feedback loops while maintaining comprehensive coverage.

---

## Purpose

Performance tests serve to:

1. **Validate Performance Characteristics:** Ensure queries and operations perform within acceptable time limits
2. **Prevent Regressions:** Catch performance regressions before they reach production
3. **Test Scalability:** Verify that the application handles larger datasets efficiently
4. **N+1 Query Prevention:** Ensure proper preloading and query optimization

---

## Identified Performance Tests

### 1. Member LiveView - Boolean Filter Performance

**File:** `test/mv_web/member_live/index_test.exs`  
**Test:** `"boolean filter performance with 150 members"`  
**Duration:** ~3.8 seconds  
**Purpose:** Validates that boolean custom field filtering performs efficiently with 150 members

**What it tests:**
- Creates 150 members (75 with `true`, 75 with `false` for a boolean custom field)
- Tests filter performance (< 1 second requirement)
- Verifies correct filtering behavior

### 2. Group LiveView - Index Performance

**File:** `test/mv_web/live/group_live/index_test.exs`  
**Describe Block:** `"performance"`  
**Tests:** 2 tests  
**Purpose:** Validates efficient page loading and member count calculation

**What it tests:**
- Page loads efficiently with many groups (no N+1 queries)
- Member count calculation is efficient

### 3. Group LiveView - Show Performance

**File:** `test/mv_web/live/group_live/show_test.exs`  
**Describe Block:** `"performance"`  
**Tests:** 2 tests  
**Purpose:** Validates efficient member list loading and slug lookup

**What it tests:**
- Member list is loaded efficiently (no N+1 queries)
- Slug lookup uses unique_slug index efficiently

### 4. Member LiveView - Membership Fee Status Performance

**File:** `test/mv_web/member_live/index_membership_fee_status_test.exs`  
**Describe Block:** `"performance"`  
**Tests:** 1 test  
**Purpose:** Validates efficient cycle loading without N+1 queries

**What it tests:**
- Cycles are loaded efficiently without N+1 queries
- Multiple members with cycles render without performance issues

### 5. Group Integration - Query Performance

**File:** `test/membership/group_integration_test.exs`  
**Describe Block:** `"Query Performance"`  
**Tests:** 1 test  
**Purpose:** Validates N+1 query prevention for group-member relationships

**What it tests:**
- Preloading groups with members avoids N+1 queries
- Query optimization for many-to-many relationships

---

## Running Slow Tests

### Local Development

**Run only fast tests (default):**
```bash
just test-fast
# or
mix test --exclude slow

# With specific files or options
just test-fast test/membership/member_test.exs
just test-fast --seed 123
```

**Run only performance tests:**
```bash
just test-slow
# or
mix test --only slow

# With specific files or options
just test-slow test/mv_web/member_live/index_test.exs
just test-slow --seed 123
```

**Run all tests (fast + slow):**
```bash
just test
# or
mix test

# With specific files or options
just test-all test/mv_web/
just test-all --max-failures 5
```

**Note:** All suite commands (`test-fast`, `test-slow`, `test-all`) support additional arguments. The suite semantics (tags) are always preserved - additional arguments are appended to the command.

### CI/CD

**Standard CI Pipeline:**
- Runs `mix test --exclude slow` for faster feedback
- Executes on every push to any branch

**Nightly Pipeline:**
- Runs `mix test --only slow` for comprehensive performance coverage
- Executes daily at 2 AM via cron trigger
- Pipeline name: `nightly-tests`

---

## Best Practices for New Performance Tests

### When to Tag as `:slow`

Tag tests as `:slow` when they:

1. **Explicitly test performance:** Tests that measure execution time or validate performance characteristics
2. **Use large datasets:** Tests that create many records (e.g., 50+ members, 100+ records)
3. **Test scalability:** Tests that verify the application handles larger workloads
4. **Validate query optimization:** Tests that ensure N+1 queries are prevented

### When NOT to Tag as `:slow`

Do NOT tag tests as `:slow` if they are:

1. **Simply slow by accident:** Tests that are slow due to inefficient setup, not intentional performance testing
2. **Slow due to bugs:** Tests that are slow because of actual performance bugs (fix the bug instead)
3. **Integration tests:** Integration tests should be tagged separately if needed (`@tag :integration`)

### Tagging Guidelines

**For single tests:**
```elixir
@tag :slow
test "boolean filter performance with 150 members" do
  # test implementation
end
```

**For describe blocks (all tests in block):**
```elixir
@moduletag :slow
describe "performance" do
  test "page loads efficiently" do
    # test implementation
  end
  
  test "member count is efficient" do
    # test implementation
  end
end
```

---

## Performance Test Structure

### Recommended Structure

```elixir
defmodule MvWeb.SomeLiveViewTest do
  use MvWeb.ConnCase, async: true
  
  # Regular tests here (not tagged)
  
  @moduletag :slow
  describe "performance" do
    test "loads efficiently without N+1 queries" do
      # Create test data
      # Measure/validate performance
      # Assert correct behavior
    end
    
    test "handles large datasets efficiently" do
      # Create large dataset
      # Measure performance
      # Assert performance requirements
    end
  end
end
```

### Performance Assertions

Performance tests should include explicit performance assertions:

```elixir
# Example: Time-based assertion
start_time = System.monotonic_time(:millisecond)
# ... perform operation ...
end_time = System.monotonic_time(:millisecond)
duration = end_time - start_time

assert duration < 1000, "Operation took #{duration}ms, expected < 1000ms"
```

```elixir
# Example: Query count assertion (using Ecto query logging)
# Verify no N+1 queries by checking query count
```

---

## Monitoring and Maintenance

### Regular Review

- **Quarterly Review:** Review slow tests quarterly to ensure they're still relevant
- **Performance Baselines:** Update performance assertions if legitimate performance improvements occur
- **Test Cleanup:** Remove or optimize tests that become redundant

### Success Metrics

- ✅ Performance tests catch regressions before production
- ✅ Standard test runs complete in < 3 minutes
- ✅ Nightly builds complete successfully
- ✅ No false positives in performance tests

### Troubleshooting

**If a performance test fails:**

1. **Check if it's a real regression:** Compare with previous runs
2. **Check CI environment:** Ensure CI has adequate resources
3. **Review test data:** Ensure test data setup is correct
4. **Check for flakiness:** Run test multiple times to verify consistency

**If a performance test is too slow:**

1. **Review test implementation:** Look for inefficiencies in test setup
2. **Consider reducing dataset size:** If still representative
3. **Split into smaller tests:** If testing multiple concerns

---

## Related Documentation

- **Test Optimization Summary:** `docs/test-optimization-summary.md`
- **Seeds Test Optimization:** `docs/test-optimization-seeds.md`
- **Testing Standards:** `CODE_GUIDELINES.md` - Section 4 (Testing Standards)
- **CI/CD Configuration:** `.drone.yml`

---

## Changelog

### 2026-01-28: Initial Setup
- Marked 5 performance test suites with `@tag :slow` or `@moduletag :slow`
- Added `test-fast`, `test-slow`, and `test-all` commands to Justfile
- Updated CI to exclude slow tests from standard runs
- Added nightly CI pipeline for slow tests
- Created this documentation