Hi I have a method that accepts a List<String> param as a parameter. I'm writing a JUnit test which needs to be able to accept the parameters as a String and then it needs converted to a List<String>
The JUnit code is:

 public void testMethodName(String params, String expectedResult){
        final String testCollection = instance.MethodName(params);
        if (null == expectedResult){
            assertNull("Should return null for unspecified value", testCollection);
            assertEquals("Should return expected value", expectedResult, testCollection);

    public Object[] parametersForTestMappingCollection(){
        final List<Object> testCases = new ArrayList<Object>();

        testCases.add(JUnitParamsRunner.$("Company Request-Other than Non Payment", "UR")); 

Its basically to test a hashmap to make sure the key returns the correct value. So I basically wanted to know how I can convert each of the strings to a List<String> so that it can be passed to the method.

JUnit tests don't take parameters.

JUnit tetsts are supposed to test existing units, not to create new untested units.

I'm not sure it that is right because when I google JUnit parameter test it gives examples of it online. It's just that I need to be able to convert it from a string to a List<String>.

There are ways and libraries that allow you to do so, but you'll need to configure it in your annotation. So far, I don't see any annotations on your method. If there aren't any, it's not a JUnit test anyway.
In any case, it would make this part pointless:

if (null == expectedResult){

since you have to configure the value of expectedResult in your testclass.

There are annotations, I just didn't include all of the code the two annotations above the method are @Test and @Parameters. The expectedResult value is the "UR" part of testCases.add(JUnitParamsRunner.$("Company Request-Other than Non Payment", "UR"));