You may use SQL*Plus to test queries with bind variables. Here is what you do before 12.2:

SQL> variable text char
SQL> exec :text:='X'

PL/SQL procedure successfully completed.

SQL> select * from DUAL where DUMMY=:text;

D
-
X

Now in 12.2 is so simple

SQL> variable text char='X'
SQL> select * from DUAL where DUMMY=:text;

D
-
X