How to test a Grunt task? Understanding and best practices

I'm a bit stuck with understanding how to write complicated Gruntfile.js and use it with tests. Am I using Grunt in a right way? I would like to ask community for help and contribute in an other way.

I'm writing a new task for Grunt and want to roll it out for wide audience on Github and npm. I want to make automated testing for this task (and I want to learn how to do it properly!).

I want to test different options combinations (about 15 by now). So, I should multiple times:

• run cleanup
• run my task with next options set
• run tests and pass options object to the test

Some non-working code to look at for better understanding:

Gruntfile:

grunt.initConfig({

    test_my_task: {
        testBasic: {
            options: {
                 //first set
            }
        },
        testIgnore: {
            options: {
                //another set
            }
        },

        //...
    }

    clean: {
        tests: ['tmp'] // mmm... clean test directory
    },

    // mmm... unit tests.
    nodeunit: {
        tests: ['test/*.js']  //tests code is in 'tests/' dir
    }
});

grunt.registerTask('test', ['test_my_task']);

I know how to check if tmp/ folder is in desired state when options object given.

The problem is putting things together.

I would ask just for template code as an answer, npo need to put working example.

PS: you can propose another testing tool, nodeunit is not a must.

PPS: crap, I could have written this in plain javascript by now! Maybe I'm doing wrong that I want to put Grunt into the unit tests? But I want to test how my task works in real environment with different options passed from Grunt...