# Simulator Unit Tests

Unit tests for the `Simulator` class are implemented in `src/g2_2025_odometry_pkg/test/test_simulator.cpp` using Google Test and ROS2 test utilities. The tests validate interval-based value generation with different interpolation types.

## Test Cases

### 1. ConstantInterval

**Description:** Verifies constant interpolation returns the same value throughout the interval.

- **Test Configuration:**
  - Single interval: t=[0, 10], y_start=5.0
  - Type: constant
- **Expected Result:**
  - Value is 5.0 at t=0, t=5, t=10
  - Value holds at 5.0 after interval (t=15)

### 2. LinearInterval

**Description:** Tests linear interpolation between start and end values.

- **Test Configuration:**
  - Single interval: t=[0, 10], y_start=0.0, y_end=10.0
  - Type: linear
- **Expected Result:**
  - Value is 0.0 at t=0
  - Value is 5.0 at t=5
  - Value is 10.0 at t=10
  - Value holds at 10.0 after interval (t=15)

### 3. QuadraticInterval

**Description:** Tests quadratic (Lagrange) interpolation through 3 points.

- **Test Configuration:**
  - Single interval: t=[0, 10], y_start=0.0, y_end=0.0, t_mid=5.0, y_mid=10.0
  - Type: quadratic
- **Expected Result:**
  - Value is 0.0 at t=0
  - Value is 10.0 at t=5 (peak)
  - Value is 0.0 at t=10
  - Value holds at 0.0 after interval (t=15)

### 4. MultipleIntervals

**Description:** Tests behavior with multiple non-overlapping intervals and gaps.

- **Test Configuration:**
  - Interval 0: t=[0, 5], constant 5.0
  - Interval 1: t=[10, 15], constant 10.0
  - Gap between t=5 and t=10
- **Expected Result:**
  - Value is 5.0 at t=2.5 (first interval)
  - Value holds at 5.0 in gap (t=7.5)
  - Value is 10.0 at t=12.5 (second interval)
  - Value holds at 10.0 after all intervals (t=20)

### 5. ValueBeforeIntervals

**Description:** Tests behavior when querying time before any interval starts.

- **Test Configuration:**
  - Single interval: t=[10, 20]
- **Expected Result:**
  - Value is 0.0 at t=5 (before interval starts)

### 6. NonExistentChannel

**Description:** Tests graceful handling of queries for unconfigured channels.

- **Test Action:** Query `get_object_value("nonexistent_channel", 5.0)`
- **Expected Result:** Returns 0.0

### 7. OverlappingIntervalsThrowsException

**Description:** Verifies that overlapping intervals are detected and rejected.

- **Test Configuration:**
  - Interval 0: t=[0, 10]
  - Interval 1: t=[5, 15] (overlaps)
- **Expected Result:** Constructor throws `std::runtime_error`

### 8. MaxIntervalsLimit

**Description:** Tests that `max_intervals` parameter limits loaded intervals.

- **Test Configuration:**
  - max_intervals=2
  - num_intervals=3 (defines 3 intervals)
- **Expected Result:**
  - Only first 2 intervals are loaded
  - Third interval values default to holding second interval's end value

## Test Infrastructure

The test class `SimulatorTest` provides:
- Static `SetUpTestSuite()` and `TearDownTestSuite()` for ROS2 init/shutdown
- Helper method `createNodeWithParams()` for creating nodes with parameter overrides