diff --git a/DEVELOPMENT.md b/DEVELOPMENT.md
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+# python-termii — Local Setup Guide
+
+A clean and lightweight Python SDK for [Termii](https://termii.com) — send SMS, OTPs, and voice messages effortlessly.
+
+---
+
+## Prerequisites
+
+Before anything else, you'll need:
+
+- A [Termii account](https://accounts.termii.com/#/register) (free to sign up)
+- Your **Termii API Key** — found in your dashboard under **Settings → API Keys**
+- Git installed on your machine
+- Python 3.8 or higher
+
+---
+
+## Step 1 — Install Python
+
+### Windows
+
+1. Go to [https://www.python.org/downloads/](https://www.python.org/downloads/)
+2. Download the latest Python 3.x installer
+3. Run the installer — **check the box that says "Add Python to PATH"** before clicking Install
+4. Verify the installation:
+
+```bash
+python --version
+```
+
+### macOS
+
+macOS ships with Python 2 (don't touch it). Install Python 3 via Homebrew:
+
+```bash
+# Install Homebrew if you don't have it
+/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
+
+# Install Python
+brew install python
+
+# Verify
+python3 --version
+```
+
+### Linux (Ubuntu/Debian)
+
+```bash
+sudo apt update
+sudo apt install python3 python3-pip python3-venv -y
+
+# Verify
+python3 --version
+```
+
+---
+
+## Step 2 — Clone the Repository
+
+```bash
+git clone https://github.com/samdoghor/python-termii.git
+cd python-termii
+```
+
+---
+
+## Step 3 — Create a Virtual Environment
+
+A virtual environment keeps your project dependencies isolated — no global pollution, no version conflicts.
+
+### Windows
+
+```bash
+python -m venv venv
+source venv/Scripts/activate
+```
+
+### macOS / Linux
+
+```bash
+python3 -m venv venv
+source venv/bin/activate
+```
+
+You'll know it's active when your terminal prompt shows `(venv)` at the front. To deactivate later, just run
+`deactivate`.
+
+---
+
+## Step 4 — Install Dependencies
+
+With the virtual environment active, install the project and its dependencies:
+
+The project has a `requirements.txt`, run this:
+
+```bash
+pip install -r requirements.txt
+```
+
+If you want to install the package itself in editable mode (so you can import it in your scripts), run:
+
+```bash
+pip install -e .
+```
+
+The `-e` flag installs it in **editable mode**, meaning changes you make to the source code are reflected immediately
+without reinstalling.
+
+---
+
+## Step 5 — Set Up Your API Key
+
+Never hardcode your API key in source files. Use an environment variable instead.
+
+### Use a `.env` file (recommended)
+
+Create a `.env` file in the project root:
+
+```
+TERMII_API_KEY=your_api_key_here
+TERMII_BASE_URL=your_base_url_here
+```
+
+> ⚠️ The `.gitignore` already excludes `.env` files. Do **not** commit your API key to version control.
+
+---
+
+## Step 6 — Run the  (Ignoring tests for now)
+
+Ignore this as test case are not yet pushed to the repo.
+
+The project includes a `test/` directory and a `test_data.py` file. Run the tests to confirm everything is wired up
+correctly:
+
+```bash
+python -m pytest test/
+```
+
+Or run the test data file directly:
+
+```bash
+python test_data.py
+```
+
+If `pytest` isn't installed:
+
+```bash
+pip install pytest
+python -m pytest test/
+```
+
+---
+
+## Step 7 — Using the SDK
+
+Here's a quick example of what using `python-termii` looks like in practice:
+
+create a file named `example.py` in the project root with the following content:
+
+```python
+import os
+from termii_py import Termii  # adjust import based on actual module structure
+
+# Initialize with your API key
+client = Termii(api_key=os.environ.get("TERMII_API_KEY"), base_url=os.environ.get("TERMII_BASE_URL"))
+
+# Send an SMS
+response = client.message.send_message(
+    to="2348012345678",  # recipient phone number (international format)
+    from_="YourSenderID",  # approved sender ID from your Termii dashboard
+    message="Hello from python-termii!",
+    type="plain",
+    channel="generic"
+)
+
+print(response)
+```
+
+```bash
+python example.py
+```
+
+there is an already a `test_data.py` file in the repo that you can use as a reference for how to call the SDK methods.
+
+```bash
+python test_data.py
+```
+
+> **Note:** Phone numbers must be in international format **without** the `+` sign (e.g., `2348012345678` for a Nigerian
+> number).
+
+---
+
+## Project Structure
+
+```
+python-termii/
+├── termii_py/          # Core SDK source code
+├── test/               # Test files
+├── test_data.py        # Sample test data / quick test runner
+├── pyproject.toml      # Project metadata and build config
+├── .gitignore
+└── LICENSE
+```
+
+---
+
+## Common Issues
+
+**`ModuleNotFoundError: No module named 'termii_py'`**
+Make sure you ran `pip install -e .` from the project root with your virtual environment active.
+
+**`python: command not found` (macOS/Linux)**
+Use `python3` instead of `python`. You can alias it: `alias python=python3`
+
+**API key not being read**
+Double-check that you exported the environment variable in the **same terminal session** you're running the script from.
+Each new terminal session starts fresh.
+
+**Invalid sender ID**
+Sender IDs must be pre-registered and approved in your Termii dashboard before use.
+
+---
+
+## Resources
+
+- [Termii API Documentation](https://developers.termii.com)
+- [Termii Dashboard](https://accounts.termii.com)
+- [Repository](https://github.com/samdoghor/python-termii)
+- [MIT License](./LICENSE)
+
+---
+
+*Built by [Samuel Doghor](https://github.com/samdoghor)*
diff --git a/termii_py/client.py b/termii_py/client.py
index 67650c1..cfe562d 100644
--- a/termii_py/client.py
+++ b/termii_py/client.py
@@ -42,6 +42,12 @@ class TermiiClient:
     def __init__(self, api_key: str = None, base_url: str = None):
         self.api_key = api_key or config.TERMII_API_KEY
         self.base_url = base_url or config.TERMII_BASE_URL
+
+        if not self.api_key:
+            raise ValueError("api_key is required. Pass it directly or set TERMII_API_KEY in your environment.")
+        if not self.base_url:
+            raise ValueError("base_url is required. Pass it directly or set TERMII_BASE_URL in your environment.")
+
         self.http = RequestHandler(self.api_key, self.base_url)
         self.sender_id = SenderIDService(self.http)
         self.message = MessageService(self.http)
diff --git a/test_data.py b/test_data.py
new file mode 100644
index 0000000..02c26f7
--- /dev/null
+++ b/test_data.py
@@ -0,0 +1,36 @@
+from termii_py import TermiiClient
+
+client = TermiiClient()  # when you initialize the client without parameters, it will automatically fetch the API key and base URL from the environment variables if they are set as TERMII_API_KEY and TERMII_BASE_URL respectively.
+# client = TermiiClient(api_key="your_api_key", base_url="your_base_url")  # you can also initialize the client with your API key and base URL
+
+# message_service = client.phonebook.fetch_phonebooks()
+
+message_service = client.message.send_message(
+    sent_to="2348031390921",
+    sent_from="CompanyName",
+    message="This is a test message",
+    channel="generic",
+    type="plain"
+
+)
+
+print(message_service.status_code)
+print(message_service.status)
+print(message_service.message)
+
+# message_service = client.template.send_message(
+#     sent_to="2348031390921",
+#     device_id="f3f4f7b0-52d8-40bc-91fc-120da11ff936",
+#     template_id="1493-csdn3-ns34w-sd3434-dfdf",
+#     data={
+#         "product_name": "Termii",
+#         "otp": 120435,
+#         "expiry_time": "10 minutes"
+#     },
+#     caption="We are excited to have you on board!",
+#     url="https://example.com/welcome-image.jpg"
+# )
+#
+# print(message_service.status_code)
+# print(message_service.status)
+# print(message_service.message)