# Wheel Data Simulator Unit Tests

Unit tests for the `DataSimulator` (Wheel) node are implemented in `src/g2_2025_odometry_pkg/test/test_wheel_simulator.cpp` using Google Test and ROS2 test utilities. The tests validate node initialization, message publishing, array structure, and data correctness.

## Test Cases

### 1. NodeInitialization

**Description:** Verifies that the Wheel DataSimulator node can be created without errors.

- **Test Action:** Create DataSimulator instance
- **Expected Result:** No exceptions thrown during construction

### 2. WheelDataPublishing

**Description:** Tests that wheel data messages are published on the correct topic.

- **Test Action:**
  - Create subscription to `simulated_wheel_data` topic
  - Create DataSimulator node
  - Spin both nodes for a short period
- **Expected Result:** At least one `std_msgs/msg/Float64MultiArray` message is received

### 3. WheelDataArraySize

**Description:** Verifies that the published array contains the correct number of wheel values.

- **Test Action:**
  - Subscribe to `simulated_wheel_data`
  - Receive a message
  - Check array size
- **Expected Result:** `data.size()` equals 4 (FL, FR, RL, RR)

### 4. ValidVelocityValues

**Description:** Tests that all wheel velocity values are valid (finite numbers).

- **Test Action:**
  - Subscribe and receive wheel data message
  - Check each value in the array
- **Expected Result:** All 4 values are finite numbers

### 5. MultipleMessagesReceived

**Description:** Tests that multiple messages are published over time.

- **Test Action:**
  - Subscribe and count received messages
  - Spin for a short duration
- **Expected Result:** Message count is greater than 0

## Test Infrastructure

The test class `WheelSimulatorTest` provides:
- Static `SetUpTestSuite()` and `TearDownTestSuite()` for ROS2 init/shutdown
- Helper method `setupBasicWheelParams()` for setting up default test parameters

## ROS2 Topics Used

| Topic | Message Type | Direction |
|-------|--------------|-----------|
| `simulated_wheel_data` | std_msgs/msg/Float64MultiArray | Published by node under test |

## Data Array Format

The published Float64MultiArray contains wheel values in the following order:

| Index | Wheel |
|-------|-------|
| 0 | Front Left (FL) |
| 1 | Front Right (FR) |
| 2 | Rear Left (RL) |
| 3 | Rear Right (RR) |