Add test for request params behavior changes (#3364) (#3440)

Co-authored-by: Tom Christie <tom@tomchristie.com>

CHANGELOG.md

@@ -28,6 +28,7 @@ Our revised [SSL documentation](docs/advanced/ssl.md) covers how to implement th
 * Ensure `certifi` and `httpcore` are only imported if required. (#3377)
 * Treat `socks5h` as a valid proxy scheme. (#3178)
 * Cleanup `Request()` method signature in line with `client.request()` and `httpx.request()`. (#3378)
+* Bugfix: When passing `params={}`, always strictly update rather than merge with an existing querystring. (#3364)
 
 ## 0.27.2 (27th August, 2024)
 

tests/models/test_requests.py

@@ -226,3 +226,16 @@ def test_request_generator_content_picklable():
     request.read()
     pickle_request = pickle.loads(pickle.dumps(request))
     assert pickle_request.content == b"test 123"
+
+
+def test_request_params():
+    request = httpx.Request("GET", "http://example.com", params={})
+    assert str(request.url) == "http://example.com"
+
+    request = httpx.Request(
+        "GET", "http://example.com?c=3", params={"a": "1", "b": "2"}
+    )
+    assert str(request.url) == "http://example.com?a=1&b=2"
+
+    request = httpx.Request("GET", "http://example.com?a=1", params={})
+    assert str(request.url) == "http://example.com"