1103 - '%s' ('%s') is a '%s', which does not describe a file.

Description
A Function parameter which can only reference a node which results in a file output references a non-file output node.
Example
Config:
Unity( 'Test' ) { .UnityInputPath = 'Code/' .UnityOutputPath = 'tmp/' } Test( 'RunTest' ) { .TestOutput = 'tmp/' .TestExecutable = 'Test' }
Output:
c:\Test\fbuild.bff(6):(1) FASTBuild Error #1103 - Test() - 'TestExecutable' ('Test') is a 'Unity', which does not describe a file. Test( 'RunTest' ) ^ \--here
Fix:
Executable( 'Test' ) { .Libraries = { 'tmp/libs/mylib.lib' } // Assume a previously define Library .LinkerOutput = 'tmp/myexe.exe' } Test( 'RunTest' ) { .TestOutput = 'tmp/' .TestExecutable = 'Test' }