Customize icon given regex on vscode-icon

I am trying to differentiate icons for my test files on a golang project on vscode. For a given file xxx.go, the test pattern is xxx_test.go

Is there a way to accomplish that on vscode-icons ?

I've tried things like: (with no luck)

 "vsicons.associations.files": [
        { "icon": "asciidoc", "extensions": ["**/*_test.go"], "format": "svg", "filename": true },
        { "icon": "asciidoc", "extensions": ["*_test.go"], "format": "svg", "filename": true },
        { "icon": "asciidoc", "extensions": ["_test.go"], "format": "svg", "filename": true },
    ],

Thanks