test: add tests for either FastMCP implementation #5075

constantinius · 2025-11-06T08:47:18Z

Issues

Closes https://linear.app/getsentry/issue/TET-1329/fastmcp-tests

Reminders

Please add tests to validate your changes, and lint your code using tox -e linters.
Add GH Issue ID & Linear ID (if applicable)
PR title should use conventional commit style (feat:, fix:, ref:, meta:)
For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

linear · 2025-11-06T08:47:21Z

TET-1329 FastMCP: tests

codecov · 2025-11-06T08:52:56Z

❌ 7 Tests Failed:

Tests completed	Failed	Passed	Skipped
27892	7	27885	2255

View the top 3 failed test(s) by shortest run time

tests.tracing.test_decorator::test_trace_decorator_no_trx

Stack Traces | 0.014s run time

tests/tracing/test_decorator.py:47: in test_trace_decorator_no_trx
    fake_debug.assert_called_once_with(
.../hostedtoolcache/Python/3.14.0.../x64/lib/python3.14/unittest/mock.py:996: in assert_called_once_with
    raise AssertionError(msg)
E   AssertionError: Expected 'mock' to be called once. Called 2 times.
E   Calls: [call('Cannot create a child span for %s. Please start a Sentry transaction before calling this function.', 'test_decorator.my_example_function'),
E    call('Cannot create a child span for %s. Please start a Sentry transaction before calling this function.', 'time.sleep')].

tests.integrations.fastmcp.test_fastmcp::test_fastmcp_mixed_sync_async_tools[fastmcp]

Stack Traces | 0.111s run time

.../integrations/fastmcp/test_fastmcp.py:1133: in test_fastmcp_mixed_sync_async_tools
    assert result1["result"] == 7
           ^^^^^^^^^^^^^^^^^
E   TypeError: 'int' object is not subscriptable

tests.integrations.fastmcp.test_fastmcp::test_fastmcp_tool_with_no_arguments[fastmcp]

Stack Traces | 0.112s run time

.../integrations/fastmcp/test_fastmcp.py:1054: in test_fastmcp_tool_with_no_arguments
    assert result["result"] == "success"
           ^^^^^^^^^^^^^^^^
E   TypeError: string indices must be integers, not 'str'

tests.integrations.fastmcp.test_fastmcp::test_fastmcp_multiple_tools[fastmcp]

Stack Traces | 0.128s run time

.../integrations/fastmcp/test_fastmcp.py:490: in test_fastmcp_multiple_tools
    result2 = call_tool_through_mcp(mcp, "tool_two", {"y": result1["result"]})
                                                           ^^^^^^^^^^^^^^^^^
E   TypeError: 'int' object is not subscriptable

tests.integrations.fastmcp.test_fastmcp::test_fastmcp_tool_with_no_arguments[fastmcp]

Stack Traces | 0.134s run time

.../integrations/fastmcp/test_fastmcp.py:1054: in test_fastmcp_tool_with_no_arguments
    assert result["result"] == "success"
           ^^^^^^^^^^^^^^^^
E   TypeError: string indices must be integers, not 'str'

tests.integrations.fastmcp.test_fastmcp::test_fastmcp_multiple_tools[fastmcp]

Stack Traces | 0.17s run time

.../integrations/fastmcp/test_fastmcp.py:490: in test_fastmcp_multiple_tools
    result2 = call_tool_through_mcp(mcp, "tool_two", {"y": result1["result"]})
                                                           ^^^^^^^^^^^^^^^^^
E   TypeError: 'int' object is not subscriptable

tests.integrations.fastmcp.test_fastmcp::test_fastmcp_mixed_sync_async_tools[fastmcp]

Stack Traces | 0.173s run time

.../integrations/fastmcp/test_fastmcp.py:1133: in test_fastmcp_mixed_sync_async_tools
    assert result1["result"] == 7
           ^^^^^^^^^^^^^^^^^
E   TypeError: 'int' object is not subscriptable

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tox.ini

sentry · 2025-11-06T10:13:29Z

tox.ini

    dramatiq: TESTPATH=tests/integrations/dramatiq
    falcon: TESTPATH=tests/integrations/falcon
    fastapi: TESTPATH=tests/integrations/fastapi
+    fastmcp: TESTPATH=tests/integrations/fastmcp


Bug: The fastmcp tox environment's TESTPATH in tox.ini line 808 points to a non-existent directory, preventing test discovery.
_{Severity: HIGH | Confidence: 1.00}

🔍 Detailed Analysis

The fastmcp tox environment's TESTPATH is incorrectly configured in tox.ini at line 808. It points to tests/integrations/fastmcp, a non-existent directory. The actual test file, test_fastmcp.py, resides in tests/integrations/mcp. This misconfiguration prevents pytest from discovering and executing any tests for the fastmcp integration suite, resulting in a silent failure where no tests are run.

💡 Suggested Fix

Update tox.ini line 808 to set fastmcp: TESTPATH=tests/integrations/mcp. This will correctly direct pytest to the location of the fastmcp integration tests.

🤖 Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not valid. Location: tox.ini#L808 Potential issue: The `fastmcp` tox environment's `TESTPATH` is incorrectly configured in `tox.ini` at line 808. It points to `tests/integrations/fastmcp`, a non-existent directory. The actual test file, `test_fastmcp.py`, resides in `tests/integrations/mcp`. This misconfiguration prevents `pytest` from discovering and executing any tests for the `fastmcp` integration suite, resulting in a silent failure where no tests are run.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

I would put the new tests in a new tests/integrations/fastmcp directory.

If we changed the TESTPATH of the fastmcp entry to be tests/integrations/mcp, then we would be running mcp tests twice in our CI.

tests/integrations/fastmcp/__init__.py

alexander-alderman-webb · 2025-11-07T14:19:10Z

There are CI failures due to version bumps picked up by generate_tox.py. We're fixing them

alexander-alderman-webb · 2025-11-13T12:35:58Z

tests/integrations/fastmcp/test_fastmcp.py

+    if len(tool_spans) > 0:
+        span = tool_spans[0]
+        assert span["op"] == OP.MCP_SERVER
+        assert span["origin"] == "auto.ai.mcp"
+        assert span["data"][SPANDATA.MCP_METHOD_NAME] == "tools/call"


When running locally I see len(tool_spans) == 0. Do we expect spans here?

The same applies to other assertions in the the suite. I think it would be good to ensure the assertions run so that we can catch regressions.

cursor · 2025-11-14T11:01:05Z

scripts/populate_tox/config.py

+        "deps": {
+            "*": ["pytest-asyncio"],
+        },
+    },


Bug: Python versioning breaks CI compatibility.

The fastmcp configuration is missing a Python version constraint. All fastmcp package versions require Python >=3.10 (visible in releases.jsonl), but the configuration doesn't specify "python": ">=3.10". This causes the GitHub Actions workflow to attempt running fastmcp tests on Python 3.8 and 3.9, which will fail since those tox environments don't exist (tox.ini only generates environments for Python 3.10+). The missing constraint also means tests might attempt to install incompatible package versions.

test: add tests for either FastMCP implementation

d306c01

test: add fastmcp to tox population script

52f09d3

constantinius marked this pull request as ready for review November 6, 2025 10:11

constantinius requested a review from a team as a code owner November 6, 2025 10:11

cursor bot reviewed Nov 6, 2025

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sentry bot reviewed Nov 6, 2025

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fix: moving fastmcp tests to separate directory

7e75235

cursor bot reviewed Nov 7, 2025

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tests/integrations/fastmcp/__init__.py Show resolved Hide resolved

Merge branch 'master' into constantinius/test/integrations/fastmcp

40ec863

constantinius requested a review from alexander-alderman-webb November 13, 2025 08:49

constantinius enabled auto-merge (squash) November 13, 2025 10:29

Run split_tox_gh_actions

029891a

alexander-alderman-webb requested changes Nov 13, 2025

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test: fix fastmcp tests

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constantinius commented Nov 6, 2025

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❌ 7 Tests Failed:

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Bug: Python versioning breaks CI compatibility.

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