Gradle: using the TestReport task with different XML file - unit-testing

Question

I have a gradle task that produces a test report as XML file.
build
└── test-results
   ├── test // result of the regular unit tests
   │   ├── TEST-SomeTest.xml
   │   └── binary
   │   ├── output.bin
   │   ├── output.bin.idx
  │   └── results.bin
  └── testCustom // result of my custom task
  └── TEST-my-lib-1.0.0.SNAPSHOT.xml
I would like to use the standard TestReport feature of gradle (test reporting) to generate an HTML report for my XML result.
def testCustom = tasks.register('testCustom') {
// This is producing the XML test result.
}
tasks.register('testCustomReport', TestReport) {
dependsOn testCustom
destinationDir = file("$buildDir/reports/tests/testCustom")
testResultDirs.from(file("$buildDir/test-results/testCustom/"))
}
tasks.named('check') {
dependsOn testCustom, testCustomReport
}
With this I get an empty reports/tests/testCustom folder:
build
└── reports
   └── tests
   ├── test
   │   ├── classes
   │   │   └── ... .html
   │   ├── css
   │   │   ├── base-style.css
   │   │   └── style.css
   │   ├── index.html
   │   ├── js
   │   │   └── report.js
   │   └── packages
   │   └── ... .html
   └── testCustom
I guess my custom TestReport task is wrongly configured.

Answer 1

I found the reason and a solution in others StackOverflow posts:
Gradle TestReport task seems to be dependent on the binary output files generated by "test" task
From source
So there is no way it will work with my XML created by my customTest task.
The alternative is to use the ant-junit library to create the report, and it works.