Simulate timeout with enough details in case no mock could be found

Author: Colin-b

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Changed
+- The `httpx.HTTPError` message issued in case no mock could be found is now a `httpx.TimeoutException` containing all information required to fix the test case (if needed).
 
 ## [0.6.0] - 2020-08-07
 ### Changed

README.md

@@ -393,6 +393,21 @@ def test_exception_raising(httpx_mock: HTTPXMock):
 
 ```
 
+Note that default behavior is to send an `httpx.TimeoutException` in case no response can be found. You can then test this kind of exception this way:
+
+```python
+import httpx
+import pytest
+from pytest_httpx import HTTPXMock
+
+
+def test_timeout(httpx_mock: HTTPXMock):
+    with httpx.Client() as client:
+        with pytest.raises(httpx.TimeoutException):
+            client.get("http://test_url")
+
+```
+
 ### How callback is selected
 
 In case more than one callback match request, the first one not yet executed (according to the registration order) will be executed.

pytest_httpx/_httpx_mock.py

@@ -94,6 +94,18 @@ def _content_match(self, request: httpx.Request) -> bool:
 
         return request.read() == self.content
 
+    def __str__(self) -> str:
+        matcher_description = f"Match {self.method or 'all'} requests"
+        if self.url:
+            matcher_description += f" on {self.url}"
+        if self.headers:
+            matcher_description += f" with {self.headers} headers"
+            if self.content is not None:
+                matcher_description += f" and {self.content} body"
+        elif self.content is not None:
+            matcher_description += f" with {self.content} body"
+        return matcher_description
+
 
 class HTTPXMock:
     def __init__(self):
@@ -170,10 +182,43 @@ def _handle_request(
         if callback:
             return callback(request=request, timeout=timeout)
 
-        raise httpx.HTTPError(
-            f"No mock can be found for {request.method} request on {request.url}.",
-            request=request,
+        raise httpx.TimeoutException(
+            self._explain_that_no_response_was_found(request), request=request
+        )
+
+    def _explain_that_no_response_was_found(self, request: httpx.Request) -> str:
+        expect_headers = set(
+            [
+                header
+                for matcher, _ in self._responses + self._callbacks
+                if matcher.headers
+                for header in matcher.headers
+            ]
         )
+        expect_body = any(
+            [
+                matcher.content is not None
+                for matcher, _ in self._responses + self._callbacks
+            ]
+        )
+
+        request_description = f"{request.method} request on {request.url}"
+        if expect_headers:
+            request_description += f" with {dict({name: value for name, value in request.headers.items() if name in expect_headers})} headers"
+            if expect_body:
+                request_description += f" and {request.read()} body"
+        elif expect_body:
+            request_description += f" with {request.read()} body"
+
+        matchers_description = "\n".join(
+            [str(matcher) for matcher, _ in self._responses + self._callbacks]
+        )
+
+        message = f"No response can be found for {request_description}"
+        if matchers_description:
+            message += f" amongst:\n{matchers_description}"
+
+        return message
 
     def _get_response(self, request: httpx.Request) -> Optional[Response]:
         responses = [