diff --git a/pyproject.toml b/pyproject.toml
index 51b9805..aebc3e3 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -30,6 +30,12 @@ deployml = "deployml.cli.cli:main"
 [tool.poetry]
 packages = [{include = "deployml", from = "src"}]
 
+[tool.poetry.group.dev.dependencies]
+pytest = "^8.0"
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+
 [tool.setuptools]
 include-package-data = true
 
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..0a6ba24
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1 @@
+# Pytest auto-discovers this file. Shared fixtures go here when we need them.
diff --git a/tests/test_helpers.py b/tests/test_helpers.py
new file mode 100644
index 0000000..709f75c
--- /dev/null
+++ b/tests/test_helpers.py
@@ -0,0 +1,84 @@
+"""Unit tests for src/deployml/utils/helpers.py.
+
+First batch — covers three patterns:
+  1. Pure functions (no mocks needed)         → generate_bucket_name
+  2. Functions that call out to the OS        → check_command  (uses mocks)
+  3. Functions that parse text                → estimate_terraform_time
+"""
+
+from unittest.mock import patch
+
+from deployml.utils.helpers import (
+    check_command,
+    estimate_terraform_time,
+    generate_bucket_name,
+)
+
+
+# ---------------------------------------------------------------------------
+# generate_bucket_name — pure function, no I/O, easiest possible test
+# ---------------------------------------------------------------------------
+
+def test_generate_bucket_name_basic():
+    # Arrange + Act
+    name = generate_bucket_name("my-project-123")
+    # Assert
+    assert name == "mlflow-artifacts-my-project-123"
+
+
+def test_generate_bucket_name_replaces_underscores():
+    # GCS bucket names disallow underscores. The helper must convert them
+    # to hyphens — otherwise a project ID like "my_project" would produce
+    # an invalid bucket name and deploy would fail at apply time.
+    name = generate_bucket_name("my_project_123")
+    assert name == "mlflow-artifacts-my-project-123"
+    assert "_" not in name
+
+
+# ---------------------------------------------------------------------------
+# check_command — calls shutil.which under the hood. We mock it so the test
+# doesn't depend on what's installed on the machine running the suite.
+# ---------------------------------------------------------------------------
+
+def test_check_command_returns_true_when_found():
+    with patch("deployml.utils.helpers.shutil.which", return_value="/usr/bin/terraform"):
+        assert check_command("terraform") is True
+
+
+def test_check_command_returns_false_when_missing():
+    with patch("deployml.utils.helpers.shutil.which", return_value=None):
+        assert check_command("nonexistent-cmd") is False
+
+
+# ---------------------------------------------------------------------------
+# estimate_terraform_time — parses terraform plan output with regex.
+# We feed it realistic snippets and assert on the returned string.
+# ---------------------------------------------------------------------------
+
+def test_estimate_terraform_time_detects_cloud_sql():
+    # Cloud SQL gets a special 20-min-per-instance estimate because
+    # provisioning a Postgres instance is the slowest part of a deploy.
+    plan_output = """
+    Terraform will perform the following actions:
+
+      # google_sql_database_instance.main will be created
+      + resource "google_sql_database_instance" "main" {
+        name = "mlflow-db"
+      }
+    """
+    result = estimate_terraform_time(plan_output)
+    assert "20 minutes" in result
+    assert "Cloud SQL" in result
+
+
+def test_estimate_terraform_time_small_stack_without_cloud_sql():
+    # Two non-SQL resources → falls into the generic resource-count branch.
+    # 2 resources × 0.5 min avg = 1 minute (clamped by max(1, ...)).
+    plan_output = """
+      # google_cloud_run_service.mlflow will be created
+      # google_cloud_run_service.fastapi will be created
+    """
+    result = estimate_terraform_time(plan_output)
+    assert result.startswith("~")
+    assert "minute" in result
+    assert "Cloud SQL" not in result