fix: add rule to prevent test files from having the same name

[dmadisetti]

📝 Summary

A common flaky failure pattern is:

ERROR tests/_messaging/test_variables.py - import file mismatch:
imported module 'test_variables' has this __file__ attribute:
  /home/runner/work/marimo/marimo/tests/_ast/test_variables.py
which is not the same as the test file we want to collect:
  /home/runner/work/marimo/marimo/tests/_messaging/test_variables.py
HINT: remove __pycache__ / .pyc files and/or use a unique basename for your test file modules

Which occurs because we have test files named the same thing (e.g. test_variables.py here).

This PR moves some of these existing files, and adds a pre commit rule to stop users duplicating additional tests.

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Project	Deployment	Actions	Updated (UTC)
marimo-docs	Ready	Preview, Comment	May 22, 2026 5:46pm

[cubic-dev-ai]

No issues found across 6 files

Architecture diagram

sequenceDiagram
    participant Dev as Developer
    participant Git as Git Hook (pre-commit)
    participant Script as check_test_filenames.py
    participant Fs as tests/ Directory
    participant Ignore as Ignored Paths

    Note over Dev,Ignore: Pre-commit Hook Flow

    Dev->>Git: git commit
    Git->>Script: python scripts/check_test_filenames.py
    Script->>Fs: Walk tests/ for test_*.py files
    Fs-->>Script: List of file paths

    Script->>Script: Check if path is ignored
    alt Path in IGNORED_PREFIXES
        Script->>Ignore: Skip path
    end

    Script->>Script: Group by filename (e.g., test_variables.py)
    Script->>Script: Check for duplicate basenames

    alt Duplicate basenames found
        Script-->>Git: Non-zero exit (1)
        Git-->>Dev: Reject commit, print duplicate names
    else No duplicates
        Script-->>Git: Zero exit (0)
        Git-->>Dev: Allow commit to proceed
    end

    Note over Dev,Ignore: Pytest Collection Context

    Dev->>Fs: Run pytest
    Fs->>Fs: Collect test files
    alt Duplicate basenames exist (blocked by hook)
        Fs->>Fs: Import clobbering occurs
        Fs-->>Dev: Import file mismatch error
    else Unique basenames (enforced by hook)
        Fs-->>Dev: Successful test collection
    end

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_{Re-trigger cubic}

[Copilot]

Pull request overview

This PR addresses a recurring pytest collection flake caused by duplicate test module basenames (pytest’s default import mode imports test files as top-level modules). It introduces a pre-commit check to enforce unique test filenames and adds/relocates several tests under new, non-colliding filenames.

Changes:

• Added a repository script to detect duplicate test basenames under tests/ and fail fast.
• Wired the duplicate-filename check into pre-commit via a local hook.
• Added/relocated multiple test modules (session/notebook, session/managers, code_mode) under unique basenames.

Reviewed changes

Copilot reviewed 2 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/_session/notebook/test_filesystem_storage.py	Adds FilesystemStorage coverage; includes a couple tests intending to validate string-path handling.
tests/_session/notebook/test_app_file_manager.py	Adds tests for load_notebook / new_notebook helpers and path resolution behavior.
tests/_session/managers/test_app_host_kernel_manager.py	Adds unit tests for AppHost kernel/queue manager adapters.
tests/_code_mode/test_code_mode_context.py	Adds/relocates comprehensive tests for AsyncCodeModeContext transaction behavior.
scripts/check_test_filenames.py	New enforcement script to prevent duplicate test basenames (core of the flake fix).
.pre-commit-config.yaml	Adds a local pre-commit hook to run the new test-filename check.

[github-actions]

🚀 Development release published. You may be able to view the changes at https://marimo.app?v=0.23.9-dev2