How to use "swift test last"?

schafdog · July 30, 2026, 7:11am

I was looking for a similar feature in maven to only run failed test when I stumbled over this. But it only says "No existing test output found." So how do I trigger "swift test" to save test results that it can use?

smontgomery · August 6, 2026, 9:57pm

It turns out this last subcommand was intended to be an experimental feature, but was incorrectly included in the help/usage by default instead of being hidden. I've filed an issue to hide it for now:

github.com/swiftlang/swift-package-manager

The 'swift test last' subcommand isn't hidden by default

opened 09:42PM - 06 Aug 26 UTC

stmontgomery

bug documentation swift test

### Is it reproducible with SwiftPM command-line tools: `swift build`, `swift te…st`, `swift package` etc? - [x] Confirmed reproduction steps with SwiftPM CLI. The description text _must_ include reproduction steps with either of command-line SwiftPM commands, `swift build`, `swift test`, `swift package` etc. ### Description There is a `last` subcommand to `swift test`, and I believe it was intended as an experimental feature but it was accidentally left un-hidden, i.e. shown to users by default in the help output: ``` ⇒ swift help test | tail -5 SUBCOMMANDS: list Lists test methods in specifier format last See 'swift help test <subcommand>' for detailed help. ⇒ swift help test last USAGE: swift test last OPTIONS: --version Show the version. -h, -help, --help Show help information. ``` It was added in https://github.com/swiftlang/swift-package-manager/pull/6861 A user on the Swift Forums recently asked about it here: > https://forums.swift.org/t/how-to-use-swift-test-last/88648 ### Expected behavior If the feature is experimental, undocumented, and incomplete, I think it should be hidden by default in the help usage; this issue tracks that. ### Actual behavior The `swift test last` subcommand is shown in help usage. ### Steps to reproduce 1. Run `swift help test` 2. See `last` included in the subcommands list, without documentation ### Swift Package Manager version/commit hash _No response_ ### Swift & OS version (output of `swift --version ; uname -a`) Swift 6.4

Finagolfin · August 7, 2026, 3:04am

You can't, as far as I know. What you can do is run all the tests, fix the ones that are failing, then if you want to just check that one you fixed named say testExitSignal, run swift test --filter testExitSignal.

schafdog · August 7, 2026, 7:29am

Well Finding the failed ones IS the issue among +500. the default is running in parallel (the help is wrong here too as it says: default is --no-parallel) which garbles the output. The work-around is to run --no-parallel or grep for the "x" which I think works

Finagolfin · August 7, 2026, 7:58am

It is worse than that: XCTest tests are run serially by default, while Testing tests are run in parallel! I argued against this crazy default, but they chose to keep it.

Yeah, pipe the output to a log file, best way to examine it.