diff --git a/tests/test_dimo.py b/tests/test_dimo.py
index 282ab2f..a0d6590 100644
--- a/tests/test_dimo.py
+++ b/tests/test_dimo.py
@@ -13,10 +13,10 @@ def test_get_full_path_with_params():
     client = DIMO(env="Dev")
     result = client._get_full_path(
         "Telemetry",
-        "/items/:item_id",
-        {"item_id": 123, "detail_id": "abc"},
+        "/items/{item_id}",
+        {"item_id": 123},
     )
-    assert result == "https://telemetry-api.dev.dimo.zone/query/items/123"
+    assert result == "https://telemetry-api.dev.dimo.zone/items/123"
 
 
 def test_get_auth_headers():
diff --git a/tests/test_request.py b/tests/test_request.py
new file mode 100644
index 0000000..b99c20e
--- /dev/null
+++ b/tests/test_request.py
@@ -0,0 +1,90 @@
+import json
+import pytest
+from requests import RequestException
+from unittest.mock import Mock
+
+from dimo.request import Request, HTTPError
+
+
+class DummyResponse:
+    def __init__(
+        self, status_code=200, headers=None, json_data=None, content=b"", txt=""
+    ):
+        self.status_code = status_code
+        self.headers = headers or {}
+        self._json_data = json_data
+        self.content = content
+        self.txt = txt
+        # .raise_for_status will be set per-test via side_effect
+
+    def json(self):
+        if isinstance(self._json_data, Exception):
+            raise self._json_data
+        return self._json_data
+
+
+@pytest.fixture
+def session():
+    return Mock()
+
+
+def make_request(session, **kwargs):
+    req = Request("POST", "https://api.example.com/endpoint", session)
+    return req(**kwargs)
+
+
+def test_json_request_body_is_serialized_and_passed_through(session):
+    data = {"foo": "bar"}
+    headers = {"Content-Type": "application/json"}
+    resp = DummyResponse(
+        status_code=200,
+        headers={"Content-Type": "application/json"},
+        json_data={"ok": True},
+    )
+    resp.raise_for_status = Mock()
+    session.request.return_value = resp
+
+    result = make_request(session, headers=headers, data=data)
+
+    # ensure data was JSON-dumped
+    _, call_kwargs = session.request.call_args
+    assert call_kwargs["data"] == json.dumps(data)
+
+    # ensure we got the parsed JSON back
+    assert result == {"ok": True}
+
+
+def test_non_json_response_returns_raw_content(session):
+    resp = DummyResponse(
+        status_code=200,
+        headers={"Content-Type": "text/plain"},
+        content=b"hello world",
+    )
+    resp.raise_for_status = Mock()
+    session.request.return_value = resp
+
+    result = make_request(session)
+    assert result == b"hello world"
+
+
+def test_http_error_wraps_json_body(session):
+    # prepare a RequestException with a response whose .json() returns a dict
+    err_resp = DummyResponse(
+        status_code=400,
+        json_data={"error": "Bad things"},
+        txt="Bad things text",
+    )
+    exc = RequestException("Bad Request")
+    exc.response = err_resp
+
+    # have raise_for_status raise that exception
+    good_resp = DummyResponse()
+    good_resp.raise_for_status = Mock(side_effect=exc)
+    session.request.return_value = good_resp
+
+    with pytest.raises(HTTPError) as ei:
+        make_request(session)
+    err = ei.value
+    assert err.status == 400
+    assert err.body == {"error": "Bad things"}
+    assert "Bad Request" in str(err)