feat(test): test_package_not_rebuilt_across_sessions_when_no_files_changed FAILED when pixi run test-fast

[xflcx1991]

Checks

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pixi, using pixi --version.

Reproducible example

Commands I ran and their output:

pixi run test-fast

    thread 'test_package_not_rebuilt_across_sessions_when_no_files_changed' panicked at crates/pixi_command_dispatcher/tests/integration/main.rs:1329:5:
    No packages should be rebuilt across sessions when no files changed, but got: ["package-b"]
    note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

  Cancelling due to test failure: 15 tests still running

pixi.toml/pyproject.toml file that reproduces my issue:
no need. just use pixi project main branch and run pixi run test-fast

pixi info output:

System
------------
       Pixi version: 0.62.2
        TLS backend: rustls
           Platform: linux-64
   Virtual packages: __unix=0=0
                   : __linux=6.18.0=0
                   : __glibc=2.42=0
                   : __cuda=13.1=0
                   : __archspec=1=zen4
          Cache dir: /home/xffish/.cache/rattler/cache
       Auth storage: /home/xffish/.rattler/credentials.json
   Config locations: /home/xffish/.config/pixi/config.toml

Global
------------
            Bin dir: /home/xffish/.pixi/bin
    Environment dir: /home/xffish/.pixi/envs
       Manifest dir: /home/xffish/.pixi/manifests/pixi-global.toml

Workspace
------------
               Name: rattler
      Manifest file: /home/xffish/github/rattler/pixi.toml
       Last updated: 03-01-2026 19:49:25

Environments
------------
        Environment: default
           Features: default
           Channels: https://prefix.dev/conda-forge
   Dependency count: 11
       Dependencies: cxx-compiler, openssl, make, pkg-config, rust, cmake, cargo-nextest, rust-src, clang, compilers, mold
   Target platforms: osx-arm64, linux-64, osx-64, win-64
    Prefix location: /home/xffish/github/rattler/.pixi/envs/default
              Tasks: rattler, build, doc, test, check

        Environment: lint
           Features: lint, default
        Solve group: default
           Channels: https://prefix.dev/conda-forge
   Dependency count: 17
       Dependencies: ruff, typos, dprint, lefthook, actionlint, shellcheck, cxx-compiler, openssl, make, pkg-config, rust, cmake, cargo-nextest, rust-src, clang, compilers, mold
   Target platforms: linux-64, osx-arm64, win-64, osx-64
    Prefix location: /home/xffish/github/rattler/.pixi/envs/lint
              Tasks: rattler, build, doc, test, check, lint, cargo-clippy, lint-fast, lefthook, typos, pre-commit-install, pre-commit-install-minimal, ruff-lint, dprint-check, ruff-format, actionlint, lint-slow, cargo-fmt, dprint-fmt

        Environment: minio
           Features: minio
           Channels: https://prefix.dev/conda-forge
   Dependency count: 5
       Dependencies: minio-server, minio-client, rattler_index, rattler, nushell
   Target platforms: osx-64, linux-64, win-64, osx-arm64
    Prefix location: /home/xffish/github/rattler/.pixi/envs/minio
              Tasks: e2e-s3-minio

        Environment: s3
           Features: s3
           Channels: https://prefix.dev/conda-forge
   Dependency count: 4
       Dependencies: awscli, rattler_index, rattler, nushell
   Target platforms: linux-64, osx-arm64, win-64, osx-64
    Prefix location: /home/xffish/github/rattler/.pixi/envs/s3
              Tasks: e2e-s3-aws

Issue description

No response

Expected behavior

test PASS

[xflcx1991]

When I run pixi run cargo nextest run --package pixi_command_dispatcher 'test_package_not_rebuilt_across_sessions_when_no_files_changed', the test passes in isolation. However, it consistently fails when running pixi run test-fast.

❯ pixi run cargo nextest run --package pixi_command_dispatcher 'test_package_not_rebuilt_across_sessions_when_no_files_changed'
    Finished `test` profile [unoptimized + debuginfo] target(s) in 0.32s
────────────
 Nextest run ID 71e64594-162b-405a-9ff3-dfe73684b613 with nextest profile: default
    Starting 1 test across 2 binaries (49 tests skipped)
        PASS [   0.216s] pixi_command_dispatcher::integration test_package_not_rebuilt_across_sessions_when_no_files_changed
────────────
     Summary [   0.217s] 1 test run: 1 passed, 49 skipped

After careful analysis, I believe the root cause is a race condition where multiple integration tests run concurrently and share the same cache/source directories, causing state pollution between tests.

I'm submitting a PR that adds a nextest.toml configuration file to run the affected tests serially, which resolves this issue.