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..7513c31
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,27 @@
+import os
+import pytest
+
+os.environ["DATABASE_URL"] = "sqlite:///:memory:"
+
+from app import create_app, db as _db
+
+
+@pytest.fixture()
+def app():
+    app = create_app()
+    app.config["TESTING"] = True
+    with app.app_context():
+        _db.create_all()
+        yield app
+        _db.session.remove()
+        _db.drop_all()
+
+
+@pytest.fixture()
+def client(app):
+    return app.test_client()
+
+
+@pytest.fixture()
+def db(app):
+    return _db
diff --git a/tests/test_health.py b/tests/test_health.py
new file mode 100644
index 0000000..74d01d7
--- /dev/null
+++ b/tests/test_health.py
@@ -0,0 +1,4 @@
+def test_health(client):
+    resp = client.get("/health")
+    assert resp.status_code == 200
+    assert resp.get_json() == {"status": "healthy"}
diff --git a/tests/test_inventory.py b/tests/test_inventory.py
new file mode 100644
index 0000000..fc4be91
--- /dev/null
+++ b/tests/test_inventory.py
@@ -0,0 +1,85 @@
+ITEM = {"sku": "SKU-001", "name": "Widget", "price": 9.99}
+
+
+def _create(client, data=None):
+    return client.post("/api/inventory/", json=data or ITEM)
+
+
+class TestCreateItem:
+    def test_success(self, client):
+        resp = _create(client)
+        assert resp.status_code == 201
+        body = resp.get_json()
+        assert body["sku"] == ITEM["sku"]
+        assert body["name"] == ITEM["name"]
+        assert body["quantity"] == 0
+
+    def test_with_optional_fields(self, client):
+        resp = _create(client, {**ITEM, "quantity": 5, "category": "tools"})
+        body = resp.get_json()
+        assert body["quantity"] == 5
+        assert body["category"] == "tools"
+
+    def test_missing_fields(self, client):
+        assert client.post("/api/inventory/", json={}).status_code == 400
+        assert client.post("/api/inventory/", json={"sku": "X", "name": "Y"}).status_code == 400
+
+    def test_duplicate_sku(self, client):
+        _create(client)
+        assert _create(client).status_code == 409
+
+
+class TestListItems:
+    def test_empty(self, client):
+        assert client.get("/api/inventory/").get_json() == []
+
+    def test_returns_all(self, client):
+        _create(client, {"sku": "A", "name": "A", "price": 1})
+        _create(client, {"sku": "B", "name": "B", "price": 2})
+        assert len(client.get("/api/inventory/").get_json()) == 2
+
+    def test_filter_by_category(self, client):
+        _create(client, {"sku": "A", "name": "A", "price": 1, "category": "tools"})
+        _create(client, {"sku": "B", "name": "B", "price": 2, "category": "parts"})
+        _create(client, {"sku": "C", "name": "C", "price": 3, "category": "tools"})
+        result = client.get("/api/inventory/?category=tools").get_json()
+        assert len(result) == 2
+        assert all(i["category"] == "tools" for i in result)
+
+    def test_filter_no_match(self, client):
+        _create(client)
+        assert client.get("/api/inventory/?category=nope").get_json() == []
+
+
+class TestGetItem:
+    def test_found(self, client):
+        iid = _create(client).get_json()["id"]
+        resp = client.get(f"/api/inventory/{iid}")
+        assert resp.status_code == 200
+        assert resp.get_json()["sku"] == ITEM["sku"]
+
+    def test_not_found(self, client):
+        assert client.get("/api/inventory/999").status_code == 404
+
+
+class TestUpdateItem:
+    def test_update_fields(self, client):
+        iid = _create(client).get_json()["id"]
+        resp = client.put(f"/api/inventory/{iid}", json={"quantity": 10, "price": 19.99})
+        assert resp.status_code == 200
+        body = resp.get_json()
+        assert body["quantity"] == 10
+        assert body["price"] == "19.99"
+
+    def test_not_found(self, client):
+        assert client.put("/api/inventory/999", json={"quantity": 1}).status_code == 404
+
+
+class TestDeleteItem:
+    def test_success(self, client):
+        iid = _create(client).get_json()["id"]
+        assert client.delete(f"/api/inventory/{iid}").status_code == 204
+        assert client.get(f"/api/inventory/{iid}").status_code == 404
+
+    def test_not_found(self, client):
+        assert client.delete("/api/inventory/999").status_code == 404
diff --git a/tests/test_members.py b/tests/test_members.py
new file mode 100644
index 0000000..c729e08
--- /dev/null
+++ b/tests/test_members.py
@@ -0,0 +1,76 @@
+import pytest
+
+
+MEMBER = {"email": "a@b.com", "name": "Alice"}
+
+
+def _create(client, data=None):
+    return client.post("/api/members/", json=data or MEMBER)
+
+
+class TestCreateMember:
+    def test_success(self, client):
+        resp = _create(client)
+        assert resp.status_code == 201
+        body = resp.get_json()
+        assert body["email"] == MEMBER["email"]
+        assert body["name"] == MEMBER["name"]
+        assert body["tier"] == "basic"
+        assert body["active"] is True
+
+    def test_custom_tier(self, client):
+        resp = _create(client, {**MEMBER, "tier": "vip"})
+        assert resp.get_json()["tier"] == "vip"
+
+    def test_missing_fields(self, client):
+        assert client.post("/api/members/", json={}).status_code == 400
+        assert client.post("/api/members/", json={"email": "x"}).status_code == 400
+        assert client.post("/api/members/", json={"name": "x"}).status_code == 400
+
+    def test_duplicate_email(self, client):
+        _create(client)
+        assert _create(client).status_code == 409
+
+
+class TestListMembers:
+    def test_empty(self, client):
+        assert client.get("/api/members/").get_json() == []
+
+    def test_returns_all(self, client):
+        _create(client, {"email": "a@b.com", "name": "A"})
+        _create(client, {"email": "b@b.com", "name": "B"})
+        assert len(client.get("/api/members/").get_json()) == 2
+
+
+class TestGetMember:
+    def test_found(self, client):
+        mid = _create(client).get_json()["id"]
+        resp = client.get(f"/api/members/{mid}")
+        assert resp.status_code == 200
+        assert resp.get_json()["email"] == MEMBER["email"]
+
+    def test_not_found(self, client):
+        assert client.get("/api/members/999").status_code == 404
+
+
+class TestUpdateMember:
+    def test_update_fields(self, client):
+        mid = _create(client).get_json()["id"]
+        resp = client.put(f"/api/members/{mid}", json={"name": "Bob", "tier": "premium"})
+        assert resp.status_code == 200
+        body = resp.get_json()
+        assert body["name"] == "Bob"
+        assert body["tier"] == "premium"
+
+    def test_not_found(self, client):
+        assert client.put("/api/members/999", json={"name": "X"}).status_code == 404
+
+
+class TestDeleteMember:
+    def test_success(self, client):
+        mid = _create(client).get_json()["id"]
+        assert client.delete(f"/api/members/{mid}").status_code == 204
+        assert client.get(f"/api/members/{mid}").status_code == 404
+
+    def test_not_found(self, client):
+        assert client.delete("/api/members/999").status_code == 404
diff --git a/tests/test_models.py b/tests/test_models.py
new file mode 100644
index 0000000..ab8aa8f
--- /dev/null
+++ b/tests/test_models.py
@@ -0,0 +1,57 @@
+from app.models.member import Member
+from app.models.inventory import InventoryItem
+
+
+class TestMemberModel:
+    def test_create_and_defaults(self, db, app):
+        m = Member(email="a@b.com", name="Alice")
+        db.session.add(m)
+        db.session.commit()
+        assert m.id is not None
+        assert m.tier == "basic"
+        assert m.active is True
+        assert m.created_at is not None
+
+    def test_to_dict(self, db, app):
+        m = Member(email="a@b.com", name="Alice", tier="vip")
+        db.session.add(m)
+        db.session.commit()
+        d = m.to_dict()
+        assert d["email"] == "a@b.com"
+        assert d["tier"] == "vip"
+        assert "created_at" in d
+
+    def test_unique_email(self, db, app):
+        import pytest
+        db.session.add(Member(email="dup@b.com", name="A"))
+        db.session.commit()
+        db.session.add(Member(email="dup@b.com", name="B"))
+        with pytest.raises(Exception):
+            db.session.commit()
+
+
+class TestInventoryItemModel:
+    def test_create_and_defaults(self, db, app):
+        i = InventoryItem(sku="SKU-1", name="Widget", price=9.99)
+        db.session.add(i)
+        db.session.commit()
+        assert i.id is not None
+        assert i.quantity == 0
+        assert i.created_at is not None
+
+    def test_to_dict(self, db, app):
+        i = InventoryItem(sku="SKU-1", name="Widget", price=9.99, category="tools")
+        db.session.add(i)
+        db.session.commit()
+        d = i.to_dict()
+        assert d["sku"] == "SKU-1"
+        assert d["price"] == "9.99"
+        assert d["category"] == "tools"
+
+    def test_unique_sku(self, db, app):
+        import pytest
+        db.session.add(InventoryItem(sku="DUP", name="A", price=1))
+        db.session.commit()
+        db.session.add(InventoryItem(sku="DUP", name="B", price=2))
+        with pytest.raises(Exception):
+            db.session.commit()