I knew you could use dummy hashes with John the Ripper (to test rules, for example), I’ve seen it mentioned in the help. It took me some time however to figure out the exact format of a dummy hash.
It’s like this:
$dummy$48336c6c30
48336c6c30 is the hexadecimal representation of string H3ll0.
The hexadecimal string following $dummy$ has to use lowercase letters. If you use uppercase letters, you’ll get the dreaded “No password hashes loaded (see FAQ)”.
Here is an example using l33t rules:
Didier Stevens 
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