In reply to Ankelih:
There are many typos in the code that you have shown. When debugging issues with uvm_config_db, every character counts.
You are doing the set() to the context “uvm_test_top_env.agt0”, but the get() is from the context “uvm_test_top”.
In the set(), the null string replaces
uvm_root::get()
In the get(), “uvm_test_top.” replaces
this.
You probably want:
uvm_config_db#(virtual v_interface)::set(null,"uvm_test_top", "vif", if0);