# Phase 9: Update Tests for Virtual Time

## Current State

All 226 existing tests pass (142 unit tests, 16 fibonacci tests, 62 integration tests, 5 simple tests, 15 doc-tests). No tests are broken by the virtual time migration — the existing tests use `update()` (without virtual time) and direct component manipulation, which still works.

## Plan

### 1. Update `tests/lib.rs` — Add Virtual Time Test Utilities

Add helper functions to the `test_utils` module:
- `create_maxspeed_clock()` — Creates a VirtualClock in MaxSpeed mode with a 333ns tick size
- `create_singlestep_clock()` — Creates a VirtualClock in SingleStep mode
- `spawn_governor()` — Spawns a RealTimeGovernor thread for a given clock
- `stop_and_wait()` — Stops the clock and waits for governor thread to finish

### 2. New Test File: `tests/virtual_time_tests.rs`

#### MaxSpeed Mode Tests
- `test_maxspeed_clock_advances` — Verify VirtualClock advances in MaxSpeed mode with governor
- `test_maxspeed_component_updates` — Verify Intel4001 updates correctly at virtual time
- `test_maxspeed_rom_access_timing` — Verify ROM data is valid after access_time elapsed in virtual time

#### SingleStep Mode Tests
- `test_singlestep_advances_one_tick` — Verify each trigger_step() advances exactly one tick
- `test_singlestep_rom_state_at_specific_time` — Verify ROM state at specific virtual times:
  - Before access_time: data not ready
  - After access_time: data valid

#### Overclocking Tests
- `test_overclocking_rom_fails_at_2mhz` — Set 2 MHz clock (250ns phase), verify ROM (500ns access) fails
- `test_overclocking_ram_fails_at_2mhz` — Same for RAM
- `test_shift_register_works_at_higher_freq` — Intel4003 (200ns access) works at 2 MHz (250ns phase >= 200ns)
- `test_component_timing_check_access_time` — Direct ComponentTiming API tests

#### Virtual Clock Integration Tests
- `test_configurable_system_creates_virtual_clock` — Verify ConfigurableSystem has a VirtualClock
- `test_configurable_system_maxspeed_execution` — Run system in MaxSpeed mode briefly, verify it works
- `test_virtual_clock_stop_exits_threads` — Verify clock.stop() causes governor to exit
- `test_pause_resume_behavior` — Verify pause stops time advancement, resume continues

### 3. Implementation Notes

- All new tests go in a separate file to avoid modifying existing passing tests
- Tests use `Arc<VirtualClock>` and `RealTimeGovernor` directly (not through ConfigurableSystem) for precise control
- Overclocking tests use `ComponentTiming::check_access_time()` directly since component-internal timing checks happen via `update_at_time()` which requires the full component thread infrastructure
- Tests that spawn governor threads must ensure proper cleanup (stop + join)