tests: remove "extern crate x"

tests/exec_unit_tests.rs

@@ -8,9 +8,6 @@
 /// ! But as the tests require running an external executable, they need to be run
 /// ! as integration tests so we can ensure that our testing-commandline binary
 /// ! has been built.
-extern crate findutils;
-extern crate walkdir;
-
 use std::env;
 use std::fs::File;
 use std::io::Read;

tests/find_exec_tests.rs

@@ -9,10 +9,6 @@
 /// ! But as the tests require running an external executable, they need to be run
 /// ! as integration tests so we can ensure that our testing-commandline binary
 /// ! has been built.
-extern crate findutils;
-extern crate tempfile;
-extern crate walkdir;
-
 use std::env;
 use std::fs::File;
 use std::io::Read;

tests/xargs_tests.rs

@@ -6,9 +6,6 @@
 
 /// ! This file contains integration tests for xargs, separate from the unit
 /// ! tests so that testing-commandline can be built first.
-extern crate findutils;
-extern crate tempfile;
-
 use std::io::{Seek, SeekFrom, Write};
 
 use assert_cmd::Command;