@@ -13,6 +13,7 @@ htmlcov
 .pytest_cache/
 .mypy_cache/
 .ruff_cache/
+*.egg-info
 
 # Visual Studio Code
 .vscode/
 
@@ -0,0 +1,36 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+# Call block to block the commit with a message.
+block() {
+  echo "$@"
+  echo "Commit blocked - see errors above."
+  exit 1
+}
+
+# Add all check functions to this space separated list.
+# They are executed in this order (see end of file).
+CHECKS="fmt lint"
+
+# Run fmt against changed files compared to origin/main
+fmt() {
+  echo "==> Running fmt on all files"
+  make fmt || block "Formatting failed"
+
+  # Re-add any files that were changed by the fixers
+  git add -u
+}
+
+lint() {
+  echo "==> Running lint on all files"
+  make lint || block "Linting failed"
+
+  # Re-add any files that were changed by the fixers
+  git add -u
+}
+
+for CHECK in $CHECKS; do
+  # Force each check into a subshell to avoid crosstalk.
+  ( $CHECK ) || exit $?
+done
@@ -1,7 +1,7 @@
 .PHONY: help fmt fmt-check lint check test install dev-install type-check clean all venv activate
 
 PYTHON := python3
-SRC_DIR := src
+SRC_DIR := tfe
 TEST_DIR := tests
 VENV := .venv
 VENV_PYTHON := $(VENV)/bin/python
@@ -59,7 +59,7 @@ type-check:
 	$(VENV_PYTHON) -m mypy $(SRC_DIR)
 
 test:
-	$(VENV_PYTHON) -m pytest
+	$(VENV_PYTHON) -m pytest -v
 
 clean:
 	find . -type f -name "*.pyc" -delete
 
@@ -13,16 +13,22 @@ requires-python = ">=3.10"
 dependencies = ["requests>=2.25.0"]
 
 [project.optional-dependencies]
-dev = ["pytest>=7.0.0", "mypy>=1.17.1", "ruff>=0.12.10"]
+dev = [
+    "pytest>=7.0.0",
+    "pytest-mock>=3.14.1",
+    "mypy>=1.17.1",
+    "ruff>=0.12.10",
+    "types-requests>=2.32.4.20250809",
+]
 
 [project.urls]
 Repository = "https://github.com/hashicorp/python-tfe"
 
 [tool.setuptools.packages.find]
-where = ["src"]
+where = ["tfe"]
 
 [tool.setuptools.package-dir]
-"" = "src"
+"" = "tfe"
 
 # Ruff configuration
 [tool.ruff]
 
@@ -0,0 +1,104 @@
+from unittest.mock import Mock, patch
+
+import pytest
+
+from tfe import client, config
+
+
+@pytest.fixture
+def test_config():
+    return config.Config(address="https://app.terraform.io", token="test-token")
+
+
+@pytest.fixture
+def mock_response():
+    response = Mock()
+    response.headers = {
+        "TFP-API-Version": "2.5.0",
+        "X-TFE-Version": "v202308-1",
+        "TFP-AppName": "HCP Terraform",
+    }
+    response.raise_for_status.return_value = None
+    return response
+
+
+class TestClient:
+    @patch("requests.Session.get")
+    def test_client_initialization(self, mock_get, test_config, mock_response):
+        """Test basic client setup works."""
+        mock_get.return_value = mock_response
+
+        client_instance = client.Client(config=test_config)
+
+        assert client_instance.config.address == "https://app.terraform.io"
+        assert client_instance.config.token == "test-token"
+        assert client_instance.base_url == "https://app.terraform.io/api/v2/"
+        assert (
+            client_instance.registry_base_url
+            == "https://app.terraform.io/api/registry/"
+        )
+
+    @patch("requests.Session.get")
+    def test_url_normalization(self, mock_get, mock_response):
+        """Test that paths get normalized with trailing slashes."""
+        mock_get.return_value = mock_response
+
+        cfg = config.Config(
+            address="https://example.com",
+            token="test",
+            base_path="/custom/api",  # no trailing slash
+            registry_base_path="/registry",  # no trailing slash
+        )
+
+        client_instance = client.Client(config=cfg)
+
+        assert client_instance.base_url == "https://example.com/custom/api/"
+        assert client_instance.registry_base_url == "https://example.com/registry/"
+
+    @patch("requests.Session.get")
+    def test_api_metadata_extraction(self, mock_get, test_config, mock_response):
+        """Test that API metadata gets extracted from response headers."""
+        mock_get.return_value = mock_response
+
+        client_instance = client.Client(config=test_config)
+
+        assert client_instance.remote_api_version == "2.5.0"
+        assert client_instance.remote_tfe_version == "v202308-1"
+        assert client_instance.app_name == "HCP Terraform"
+
+    @patch("requests.Session.get")
+    def test_cloud_vs_enterprise_detection(self, mock_get, test_config):
+        """Test detection between cloud and enterprise instances."""
+        # Test HCP Terraform (cloud)
+        cloud_response = Mock()
+        cloud_response.headers = {"TFP-AppName": "HCP Terraform"}
+        cloud_response.raise_for_status.return_value = None
+        mock_get.return_value = cloud_response
+
+        cloud_client = client.Client(config=test_config)
+        assert cloud_client.is_cloud() is True
+        assert cloud_client.is_enterprise() is False
+
+        # Test Terraform Enterprise
+        enterprise_response = Mock()
+        enterprise_response.headers = {"TFP-AppName": "Terraform Enterprise"}
+        enterprise_response.raise_for_status.return_value = None
+        mock_get.return_value = enterprise_response
+
+        enterprise_client = client.Client(config=test_config)
+        assert enterprise_client.is_cloud() is False
+        assert enterprise_client.is_enterprise() is True
+
+    @patch("requests.Session.get")
+    def test_fake_api_version_for_testing(self, mock_get, test_config, mock_response):
+        """Test the fake API version setter for testing scenarios."""
+        mock_get.return_value = mock_response
+
+        client_instance = client.Client(config=test_config)
+
+        # Original version from mock
+        assert client_instance.remote_api_version == "2.5.0"
+
+        # Set fake version
+        client_instance.set_fake_remote_api_version("3.0.0")
+        assert client_instance.remote_api_version == "3.0.0"
@@ -0,0 +1,97 @@
+import pytest
+import requests
+
+from tfe import config
+
+
+@pytest.fixture(autouse=True)
+def reset_environment(monkeypatch):
+    """Reset environment variables before each test."""
+    monkeypatch.delenv("TFE_ADDRESS", raising=False)
+    monkeypatch.delenv("TFE_TOKEN", raising=False)
+    monkeypatch.delenv("TFE_HOST", raising=False)
+    monkeypatch.setenv("TFE_TOKEN", "abc123")
+    yield
+
+
+@pytest.fixture
+def cfg():
+    """Provide a fresh Config instance with clean environment."""
+    return config.Config()
+
+
+@pytest.fixture
+def test_session():
+    """Provide a clean requests session without default headers."""
+    session = requests.Session()
+    session.headers["User-Agent"] = "test"
+    session.headers["Authorization"] = "Bearer test"
+    return session
+
+
+class TestConfig:
+    def test_default_config(self, cfg):
+        """Test that default configuration values are set correctly."""
+        assert cfg.address == config.DEFAULT_ADDRESS
+        assert cfg.base_path == config.DEFAULT_BASE_PATH
+        assert cfg.registry_base_path == config.DEFAULT_REGISTRY_PATH
+        assert isinstance(cfg.http_client, requests.Session)
+        assert "User-Agent" in cfg.http_client.headers
+        assert cfg.retry_log_hook is None
+        assert cfg.retry_server_errors is False
+
+    def test_env_address_and_token(self, monkeypatch):
+        """Test that environment variables TFE_ADDRESS and TFE_TOKEN are read correctly."""
+        monkeypatch.setenv("TFE_ADDRESS", "https://custom.tfe")
+        cfg = config.Config()
+        assert cfg.address == "https://custom.tfe"
+        assert cfg.token == "abc123"
+
+    def test_env_host_fallback(self, monkeypatch):
+        """Test that TFE_HOST is used as fallback when TFE_ADDRESS is not set."""
+        monkeypatch.setenv("TFE_HOST", "host.tfe")
+        cfg = config.Config()
+        assert cfg.address == "https://host.tfe"
+
+    def test_explicit_address_override(self):
+        """Test that explicitly passed address overrides environment variables."""
+        cfg = config.Config(address="https://explicit.tfe")
+        assert cfg.address == "https://explicit.tfe"
+
+    def test_headers_update(self):
+        """Test that custom headers are properly merged with default headers."""
+        custom_headers = {"Authorization": "Bearer testtoken", "X-Test": "yes"}
+        cfg = config.Config(headers=custom_headers)
+        assert "Authorization" in cfg.http_client.headers
+        assert cfg.http_client.headers["Authorization"] == "Bearer testtoken"
+        assert "X-Test" in cfg.http_client.headers
+        assert cfg.http_client.headers["X-Test"] == "yes"
+        assert "User-Agent" in cfg.http_client.headers
+
+    def test_retry_log_hook_and_server_errors(self):
+        """Test that retry configuration is properly set."""
+
+        def dummy_hook(retries, response):
+            pass
+
+        cfg = config.Config(retry_log_hook=dummy_hook, retry_server_errors=True)
+        assert cfg.retry_log_hook == dummy_hook
+        assert cfg.retry_server_errors is True
+
+    def test_custom_session(self, test_session):
+        """Test that User-Agent is set when session has no default User-Agent."""
+        cfg = config.Config(http_client=test_session)
+        assert "User-Agent" in cfg.http_client.headers
+        assert cfg.http_client.headers["User-Agent"] == "test"
+        assert cfg.http_client.headers["Authorization"] == "Bearer test"
+
+    def test_validate_config(self, monkeypatch):
+        """Test that configuration validation works as expected."""
+        with pytest.raises(ValueError, match="API token is required") as _:
+            monkeypatch.setenv("TFE_TOKEN", "")
+            _ = config.Config(token="")
+
+        with pytest.raises(ValueError, match="Address must include protocol") as _:
+            monkeypatch.setenv("TFE_TOKEN", "test-token")
+            monkeypatch.setenv("TFE_ADDRESS", "test.foo.bar")
+            _ = config.Config()
@@ -6,6 +6,7 @@
 workspaces, runs, state files, and other TFE/TFC resources.
 """
 
-from .client import TerraformEnterpriseClient
+from tfe.client import Client, TFEClientError
+from tfe.config import Config
 
-__all__ = ["TerraformEnterpriseClient"]
+__all__ = ["Client", "TFEClientError", "Config"]