I have a swift packet with UIKit import. Unfortunately there is no way to build it using swift build. That's why tried 3 different ways to use mull-xctests.

1. I generate a project from a SPM with swift package generate-xcodeproj. Then I build it with xcodebuild build-for-testing -project PSBCore.xcodeproj -scheme PSBCore-Package -destination "platform=iOS Simulator,name=iPhone 11 Pro" OTHER_SWIFT_FLAGS="\$(inherited) -embed-bitcode" OTHER_CFLAGS="\$(inherited) -fembed-bitcode" LD="$(which mull-ld)" OTHER_LDFLAGS="\$(inherited) -Xmull --linker=clang -Xmull --linker-flavor=clang". It succeed. Then when I run mull-xctestrun -Xxcodebuild -destination -Xxcodebuild "platform=iOS Simulator,name=iPhone 11 Pro" --test-target PSBCoreTests /path/to/Library/Developer/Xcode/DerivedData/PSBCore-btiytljcqmsisacjtlzuldouejsz/Build/Products/PSBCore-Package_iphonesimulator15.0-x86_64.xctestrun and get [info] No mutants found. Mutation score: infinitely high
2. I even tried to test the project if the command similar to above, but if test instead of building-for-testing. After that I tried mull-xctest /path/to/Library/Developer/Xcode/DerivedData/PSBCore-btiytljcqmsisacjtlzuldouejsz/Build/Products/Debug-iphonesimulator/PSBCoreTests.xctest. It also gives me following:

[info] Warm up run (threads: 1)
       [################################] 1/1. Finished in 45ms
[info] Baseline run (threads: 1)
       [################################] 1/1. Finished in 41ms
[info] No mutants found. Mutation score: infinitely high

3. I've also tried to build a SPM with the command from the 1st, but without generating a Project file. This gives me an error:

x86_64-apple-ios11.0-simulator: No such file or directory
Command Ld failed with a nonzero exit code

why is there x86_64-apple-ios11.0-simulator? I'm using Xcode 13.0, which doesn't seem to have ios11 simulator.

What I'm doing wrong? Pls, help me.

Getting error on mull-ld launch and during xcodebuild setup:

dyld: Library not loaded: /usr/local/opt/llvm/lib/libLLVM.dylib
  Referenced from: /usr/local/bin/mull-ld
  Reason: image not found
Command Ld failed with a nonzero exit code

We are looking for a tool to implement Mutation Tests on iOS side in huge project. Do you guys have any ETA about releasing this library? Is this already usable?

I build your test project StubKit with command

xcodebuild build-for-testing \
  -project StubKit.xcodeproj -scheme StubKit-Package \
  -destination "platform=iOS Simulator,name=iPhone 8" \
  OTHER_SWIFT_FLAGS="\$(inherited) -embed-bitcode" \
  OTHER_CFLAGS="\$(inherited) -fembed-bitcode" \
  LD="$(which mull-ld)" \
  OTHER_LDFLAGS="\$(inherited) \
    -Xmull --linker=clang \
    -Xmull --linker-flavor=clang"

Then I try to find mutation with the following different --workers= values: 1, 2,4, 8, 9, 10. and finally, no parameter at all. Like follows:

mull-xctestrun \              
  -Xxcodebuild -destination \
  -Xxcodebuild "platform=iOS Simulator,name=iPhone 8" \
  --test-target StubKitTests /Path/to/Library/Developer/Xcode/DerivedData/StubKit-errbmrafikpnlmgukqsogexfeeyk/Build/Products/StubKit-Package_iphonesimulator14.1-x86_64.xctestrun 
 --workers=1

all of them produces different Mutation scores corresponding: 0%, 55%, 66%, 77%, 44%, 77%.

It seems like workers don't continue to get the scheduled jobs. And the correct result is only available, when the number of workers are equal to number of mutants found. That become an issue for projects having more than 16 mutants ^.^

It seems like there is a bug. Could you fix it or explain, how I could fix it by myself?