Why does my simple function not display output

Shell Programming and Scripting
1

I type the following command:
echo "Hello World"
and get output

when I create a function to do the same display, I did not get output

here is my function:

testscript()
{
  echo "Hello World"
}
2

Welcome!
You have defined the function.
Now run it:

testscript

Note that in shell you run a function without ( )
A function behaves like a command.