XUnitTestEngine produces a command line which does not work if full path of runner contains whitespaces.
Here is a patch for src/unit/engine/XUnitTestEngine.php:
$xunit = $this->projectRoot.DIRECTORY_SEPARATOR.$this->xunitHintPath; if (file_exists($xunit) && $this->xunitHintPath !== null) { - $this->testEngine = Filesystem::resolvePath($xunit); + $this->testEngine = '"'.Filesystem::resolvePath($xunit).'"'; } else if (Filesystem::binaryExists('xunit.console.clr4.exe')) { $this->testEngine = 'xunit.console.clr4.exe';