How to Pass a Form to a Handler in Ratpack unit test

Question

How do I pass a mocked Form object to a Handler in a unit test? Here's the reference I got so far:

https://ratpack.io/manual/current/testing.html

https://danhyun.github.io/2016-gr8confus-testing-ratpack-apps/

Here is the code for my Handler:

void handle(Context context) throws Exception
{
    def queryParams = context.request.queryParams
    context.parse(Form).then {form ->
        String mnemonic = queryParams ['mnemonic']
        String series = queryParams ['series']
        String volume = queryParams ['volume']
        String issue = queryParams ['issue']
        UploadedFile cover = form.file("cover")
    ...
}

This is a snippet of the unit test so far:

def form = Mock(Form)
form.file(_) >> Mock(UploadedFile)
def result = GroovyRequestFixture.handle(handler) {
        RequestFixture fixture ->
          fixture.uri("/task/node-asset/update-cover-image?"+
          "mnemonic=$mnemonic&series=$mnemonic&volume=$volume&issue=$issue")
          //Pass Mock Form
}