test is a command-line utility found in Unix, Plan 9, and Unix-like operating systems that evaluates conditional expressions.
test was turned into a shell builtin command in 1981 with UNIX System III and at the same time made available under the alternate name [.
The version of test bundled in GNU coreutils was written by Kevin Braunsdorf and Matthew Bradburn.
[2] The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities.
In portable shell scripts, the same effect may be achieved by connecting multiple invocations of test together with the && and || operators and parentheses.