Adds README file for libcan/test directory

test/README.md

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+
+# libcan/tests README
+
+This README provides an overview of the main test files and directories in the `libcan/tests` folder. It summarizes the purpose and key logic of each test, focusing on files and directories with meaningful content.
+
+---
+
+## core/src/main.cpp
+- Sets up and runs Google Test suite for core CAN frame logic.
+- `addInput`: Creates CAN CC frames, handles edge cases (e.g., DLC > 8), and checks frame validity.
+- Uses `testing::InitGoogleTest(&argc, argv)` to initialize and run all tests.
+
+## core/fuzz/src/protocol_frame_fuzz_test.cpp
+- Fuzz tests for CAN protocol frame handling.
+- Generates frames with all valid data sizes, especially for DLC > 8.
+- Ensures byte size is capped at 8 and asserts correct frame value handling.
+
+## isotp/send.py
+- Python test for sending CAN messages using the `isotp` library.
+- Opens a socket on a virtual CAN interface (`vcan`), sets RX and TX addresses.
+- Sends a message that fits into a single CAN frame.
+
+## isotp/canfd.py
+- Python test for sending CAN FD messages.
+- Specifies arbitration ID and uses SocketCAN on `vcan0` channel.
+- Sends messages over the bus using the defined interface.
+
+## linux/socketcan/src/main.cpp
+- Entry point for running all SocketCAN-related tests using Google Test.
+
+## linux/socketcan/src/soc_shutdown_test.cpp
+- Simulates SoC (State of Charge) shutdown sequence for OrionBMS 2 via SocketCAN and `vcan0`.
+- Sets up test suite, simulates SoC from 100% to 0%, sends messages, and checks assertions.
+- Detects low battery (18% SoC), triggers shutdown signal to motor controller/inverter.
+- Handles shutdown messaging and checks for CAN frame acknowledgements from Sevcon Gen4 controller.
+
+## rp2040/mcp2515/src/main.cpp
+- Runs all tests for MCP2515 CAN controller on RP2040 platform.
+
+## rp2040/mcp2515/src/provider_test.cpp
+- Sets up provider tests for SPI communication (init, set, read, write).
+- Registers raw IRQ handler on current core for testing interrupt handling.
+
+## rp2040/stubs/include/hardware/gpio.stub.h
+- Stub for Pico SDK hardware GPIO header.
+- Simulates GPIO IRQ levels and pin behavior for host-based tests.
+
+---
+
+
+### Test Cases Summary
+
+Below is a list of the main test cases covered in this directory:
+
+- **Core CAN Frame Tests**
+	- Valid CAN CC frame
+	- Valid CAN CC frame (extended ID)
+	- Edge-case: DLC above 8 (truncation)
+	- Invalid CAN FD remote frame
+	- Invalid CC frame with DLC overflow
+	- Invalid CC frame with extended ID but no IDE bit
+	- Valid CAN FD frame
+
+- **Fuzz Tests**
+	- All valid data sizes for CAN CC frames
+	- All valid data sizes with DLC above 8
+
+- **ISOTP Python Tests**
+	- Single-frame message send/receive
+
+- **CAN FD Python Tests**
+	- CAN FD message send with custom arbitration ID and DLC
+
+- **SocketCAN Tests (Linux)**
+	- Linear SoC depletion and shutdown trigger simulation
+		- Simulates OrionBMS 2 sending SoC from 100% to 0%
+		- Detects low battery (≤18%) and sends shutdown signal
+		- Sends SDO shutdown command to Sevcon Gen4 motor controller
+		- Checks for CAN frame acknowledgement from Sevcon
+
+- **RP2040 MCP2515 Provider Tests**
+	- SPI initialization, format, read/write
+	- Register raw IRQ handler on current core
+
+- **RP2040 GPIO Stub**
+	- Simulates GPIO IRQ levels and pin behavior for host-based tests
+
+---
+This summary provides a quick reference to the types of tests implemented in the directory. For details, see the relevant test source files.