Need to write an expression to find the count

[#1]

Hi All,

I have 3 columns User Id, Name , Test Score with values ,but there are null values for Test score alone,

I need to write an expression to find the count of User Id's with Test Score to find out the percentage of Users who have completed the tests

Attached is the data sheet.

Tried with the below expression but it failed..

count(if not isnull(testscore), testscore))

[tresesco]

try like:

=count(if (len(trim([Test Score]))>0, [Test Score]))