fix clippy tests

tests/by-util/test_cat.rs

@@ -485,7 +485,7 @@ fn test_dev_random() {
 }
 
 /// Reading from /dev/full should return an infinite amount of zero bytes.
-/// Wikipedia says there is support on Linux, FreeBSD, and NetBSD.
+/// Wikipedia says there is support on Linux, FreeBSD, and `NetBSD`.
 #[test]
 #[cfg(any(target_os = "linux", target_os = "freebsd", target_os = "netbsd"))]
 fn test_dev_full() {

tests/by-util/test_chcon.rs

@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 // spell-checker:ignore (jargon) xattributes
-
+#![allow(clippy::missing_errors_doc, clippy::similar_names)]
 #![cfg(feature = "feat_selinux")]
 
 use std::ffi::CString;

tests/by-util/test_chmod.rs

@@ -2,6 +2,7 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
+
 use crate::common::util::{AtPath, TestScenario, UCommand};
 use std::fs::{metadata, set_permissions, OpenOptions, Permissions};
 use std::os::unix::fs::{OpenOptionsExt, PermissionsExt};
@@ -32,12 +33,14 @@ fn make_file(file: &str, mode: u32) {
 fn run_single_test(test: &TestCase, at: &AtPath, mut ucmd: UCommand) {
     make_file(&at.plus_as_string(TEST_FILE), test.before);
     let perms = at.metadata(TEST_FILE).permissions().mode();
-    if perms != test.before {
-        panic!(
-            "{}: expected: {:o} got: {:o}",
-            "setting permissions on test files before actual test run failed", test.after, perms
-        );
-    }
+
+    assert!(
+        perms == test.before,
+        "{}: expected: {:o} got: {:o}",
+        "setting permissions on test files before actual test run failed",
+        test.after,
+        perms
+    );
 
     for arg in &test.args {
         ucmd.arg(arg);
@@ -52,9 +55,13 @@ fn run_single_test(test: &TestCase, at: &AtPath, mut ucmd: UCommand) {
     }
 
     let perms = at.metadata(TEST_FILE).permissions().mode();
-    if perms != test.after {
-        panic!("{}: expected: {:o} got: {:o}", ucmd, test.after, perms);
-    }
+    assert!(
+        perms == test.after,
+        "{}: expected: {:o} got: {:o}",
+        ucmd,
+        test.after,
+        perms
+    );
 }
 
 fn run_tests(tests: Vec<TestCase>) {
@@ -128,6 +135,7 @@ fn test_chmod_octal() {
 
 #[test]
 #[allow(clippy::unreadable_literal)]
+#[allow(clippy::too_many_lines)]
 // spell-checker:disable-next-line
 fn test_chmod_ugoa() {
     let tests = vec![

tests/by-util/test_chown.rs

@@ -29,9 +29,8 @@ fn skipping_test_is_okay(result: &CmdResult, needle: &str) -> bool {
         if is_ci() && result.stderr_str().contains(needle) {
             println!("test skipped:");
             return true;
-        } else {
-            result.success();
         }
+        result.success();
     }
     false
 }

tests/by-util/test_cp.rs

@@ -2298,9 +2298,9 @@ fn test_closes_file_descriptors() {
 #[cfg(any(target_os = "linux", target_os = "android"))]
 #[test]
 fn test_cp_sparse_never_empty() {
+    const BUFFER_SIZE: usize = 4096 * 4;
     let (at, mut ucmd) = at_and_ucmd!();
 
-    const BUFFER_SIZE: usize = 4096 * 4;
     let buf: [u8; BUFFER_SIZE] = [0; BUFFER_SIZE];
 
     at.make_file("src_file1");
@@ -2318,10 +2318,10 @@ fn test_cp_sparse_never_empty() {
 #[cfg(any(target_os = "linux", target_os = "android"))]
 #[test]
 fn test_cp_sparse_always_empty() {
+    const BUFFER_SIZE: usize = 4096 * 4;
     for argument in ["--sparse=always", "--sparse=alway", "--sparse=al"] {
         let (at, mut ucmd) = at_and_ucmd!();
 
-        const BUFFER_SIZE: usize = 4096 * 4;
         let buf: [u8; BUFFER_SIZE] = [0; BUFFER_SIZE];
 
         at.make_file("src_file1");
@@ -2338,9 +2338,9 @@ fn test_cp_sparse_always_empty() {
 #[cfg(any(target_os = "linux", target_os = "android"))]
 #[test]
 fn test_cp_sparse_always_non_empty() {
+    const BUFFER_SIZE: usize = 4096 * 16 + 3;
     let (at, mut ucmd) = at_and_ucmd!();
 
-    const BUFFER_SIZE: usize = 4096 * 16 + 3;
     let mut buf: [u8; BUFFER_SIZE] = [0; BUFFER_SIZE];
     let blocks_to_touch = [buf.len() / 3, 2 * (buf.len() / 3)];
 
@@ -2408,12 +2408,11 @@ fn test_cp_sparse_never_reflink_always() {
 #[cfg(feature = "truncate")]
 #[test]
 fn test_cp_reflink_always_override() {
-    let scene = TestScenario::new(util_name!());
-
     const DISK: &str = "disk.img";
     const ROOTDIR: &str = "disk_root/";
     const USERDIR: &str = "dir/";
     const MOUNTPOINT: &str = "mountpoint/";
+    let scene = TestScenario::new(util_name!());
 
     let src1_path: &str = &[MOUNTPOINT, USERDIR, "src1"].concat();
     let src2_path: &str = &[MOUNTPOINT, USERDIR, "src2"].concat();
@@ -2545,12 +2544,12 @@ fn test_no_preserve_mode() {
     let umask: u16 = 0o022;
     ucmd.arg("file")
         .arg("dest")
-        .umask(umask as libc::mode_t)
+        .umask(libc::mode_t::from(umask))
         .succeeds()
         .no_stderr()
         .no_stdout();
     // remove sticky bit, setuid and setgid bit; apply umask
-    let expected_perms = PERMS_ALL & !0o7000 & !umask as u32;
+    let expected_perms = PERMS_ALL & !0o7000 & u32::from(!umask);
     assert_eq!(
         at.plus("dest").metadata().unwrap().mode() & 0o7777,
         expected_perms
@@ -5477,16 +5476,17 @@ fn test_dir_perm_race_with_preserve_mode_and_ownership() {
         let start_time = std::time::Instant::now();
         // wait for cp to create dirs
         loop {
-            if start_time.elapsed() >= timeout {
-                panic!("timed out: cp took too long to create destination directory")
-            }
+            assert!(
+                start_time.elapsed() < timeout,
+                "timed out: cp took too long to create destination directory"
+            );
             if at.dir_exists(&format!("{}/{}", DEST_DIR, SRC_DIR)) {
                 break;
             }
             std::thread::sleep(Duration::from_millis(100));
         }
         let mode = at.metadata(&format!("{}/{}", DEST_DIR, SRC_DIR)).mode();
-        #[allow(clippy::unnecessary_cast)]
+        #[allow(clippy::unnecessary_cast, clippy::cast_lossless)]
         let mask = if attr == "mode" {
             libc::S_IWGRP | libc::S_IWOTH
         } else {

tests/by-util/test_date.rs

@@ -263,7 +263,7 @@ fn test_date_set_mac_unavailable() {
 
 #[test]
 #[cfg(all(unix, not(target_os = "macos")))]
-/// TODO: expected to fail currently; change to succeeds() when required.
+/// TODO: expected to fail currently; change to `succeeds()` when required.
 fn test_date_set_valid_2() {
     if geteuid() == 0 {
         let result = new_ucmd!()
@@ -288,10 +288,11 @@ fn test_date_for_invalid_file() {
 #[test]
 #[cfg(unix)]
 fn test_date_for_no_permission_file() {
-    let (at, mut ucmd) = at_and_ucmd!();
+    use std::os::unix::fs::PermissionsExt;
     const FILE: &str = "file-no-perm-1";
 
-    use std::os::unix::fs::PermissionsExt;
+    let (at, mut ucmd) = at_and_ucmd!();
+
     let file = std::fs::OpenOptions::new()
         .create(true)
         .truncate(true)
@@ -328,7 +329,7 @@ fn test_date_for_file() {
 
 #[test]
 #[cfg(all(unix, not(target_os = "macos")))]
-/// TODO: expected to fail currently; change to succeeds() when required.
+/// TODO: expected to fail currently; change to `succeeds()` when required.
 fn test_date_set_valid_3() {
     if geteuid() == 0 {
         let result = new_ucmd!()
@@ -342,7 +343,7 @@ fn test_date_set_valid_3() {
 
 #[test]
 #[cfg(all(unix, not(target_os = "macos")))]
-/// TODO: expected to fail currently; change to succeeds() when required.
+/// TODO: expected to fail currently; change to `succeeds()` when required.
 fn test_date_set_valid_4() {
     if geteuid() == 0 {
         let result = new_ucmd!()
@@ -412,8 +413,8 @@ fn test_date_overflow() {
 
 #[test]
 fn test_date_parse_from_format() {
-    let (at, mut ucmd) = at_and_ucmd!();
     const FILE: &str = "file-with-dates";
+    let (at, mut ucmd) = at_and_ucmd!();
 
     at.write(
         FILE,

tests/by-util/test_df.rs

@@ -3,6 +3,13 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 // spell-checker:ignore udev pcent iuse itotal iused ipcent
+#![allow(
+    clippy::similar_names,
+    clippy::cast_possible_truncation,
+    clippy::cast_sign_loss,
+    clippy::float_cmp
+)]
+
 use std::collections::HashSet;
 
 use crate::common::util::TestScenario;

tests/by-util/test_dircolors.rs

@@ -200,15 +200,15 @@ TERM {term_pattern}
             .no_stderr();
     }
 
-    let expectation_if_match = r#"
+    let expectation_if_match = r"
 LS_COLORS='*.term_matching=00;38;5;61:';
 export LS_COLORS
-"#
+"
     .trim_start();
-    let expectation_if_no_match = r#"
+    let expectation_if_no_match = r"
 LS_COLORS='';
 export LS_COLORS
-"#
+"
     .trim_start();
 
     // sanity checks

tests/by-util/test_du.rs

@@ -545,7 +545,7 @@ fn test_du_h_flag_empty_file() {
 #[test]
 fn test_du_h_precision() {
     let test_cases = [
-        (133456345, "128M"),
+        (133_456_345, "128M"),
         (12 * 1024 * 1024, "12M"),
         (8500, "8.4K"),
     ];

tests/by-util/test_env.rs

@@ -3,6 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 // spell-checker:ignore (words) bamf chdir rlimit prlimit COMSPEC cout cerr FFFD
+#![allow(clippy::missing_errors_doc)]
 
 use crate::common::util::TestScenario;
 #[cfg(unix)]
@@ -555,28 +556,28 @@ fn test_env_parsing_errors() {
         .stderr_is("env: invalid sequence '\\a' in -S\n");
 
     ts.ucmd()
-        .arg(r#"-S\|\&\;"#) // no quotes, invalid escape sequence |
+        .arg(r"-S\|\&\;") // no quotes, invalid escape sequence |
         .fails()
         .code_is(125)
         .no_stdout()
         .stderr_is("env: invalid sequence '\\|' in -S\n");
 
     ts.ucmd()
-        .arg(r#"-S\<\&\;"#) // no quotes, invalid escape sequence <
+        .arg(r"-S\<\&\;") // no quotes, invalid escape sequence <
         .fails()
         .code_is(125)
         .no_stdout()
         .stderr_is("env: invalid sequence '\\<' in -S\n");
 
     ts.ucmd()
-        .arg(r#"-S\>\&\;"#) // no quotes, invalid escape sequence >
+        .arg(r"-S\>\&\;") // no quotes, invalid escape sequence >
         .fails()
         .code_is(125)
         .no_stdout()
         .stderr_is("env: invalid sequence '\\>' in -S\n");
 
     ts.ucmd()
-        .arg(r#"-S\`\&\;"#) // no quotes, invalid escape sequence `
+        .arg(r"-S\`\&\;") // no quotes, invalid escape sequence `
         .fails()
         .code_is(125)
         .no_stdout()
@@ -590,14 +591,14 @@ fn test_env_parsing_errors() {
         .stderr_is("env: invalid sequence '\\`' in -S\n");
 
     ts.ucmd()
-        .arg(r#"-S'\`\&\;'"#) // single quotes, invalid escape sequence `
+        .arg(r"-S'\`\&\;'") // single quotes, invalid escape sequence `
         .fails()
         .code_is(125)
         .no_stdout()
         .stderr_is("env: invalid sequence '\\`' in -S\n");
 
     ts.ucmd()
-        .arg(r#"-S\`"#) // ` escaped without quotes
+        .arg(r"-S\`") // ` escaped without quotes
         .fails()
         .code_is(125)
         .no_stdout()
@@ -611,14 +612,14 @@ fn test_env_parsing_errors() {
         .stderr_is("env: invalid sequence '\\`' in -S\n");
 
     ts.ucmd()
-        .arg(r#"-S'\`'"#) // ` escaped in single quotes
+        .arg(r"-S'\`'") // ` escaped in single quotes
         .fails()
         .code_is(125)
         .no_stdout()
         .stderr_is("env: invalid sequence '\\`' in -S\n");
 
     ts.ucmd()
-        .args(&[r#"-S\🦉"#]) // ` escaped in single quotes
+        .args(&[r"-S\🦉"]) // ` escaped in single quotes
         .fails()
         .code_is(125)
         .no_stdout()
@@ -1068,11 +1069,11 @@ mod tests_split_iterator {
     #[test]
     fn split_single_quotes() {
         split_ok(&[
-            (r#"''"#, &[r#""#]),
-            (r#"'a'"#, &[r#"a"#]),
-            (r#"'\\'"#, &[r#"\"#]),
-            (r#"' \\ '"#, &[r#" \ "#]),
-            (r#"'#'"#, &[r#"#"#]),
+            (r"''", &[r""]),
+            (r"'a'", &[r"a"]),
+            (r"'\\'", &[r"\"]),
+            (r"' \\ '", &[r" \ "]),
+            (r"'#'", &[r"#"]),
         ]);
     }
 
@@ -1094,12 +1095,12 @@ mod tests_split_iterator {
     #[test]
     fn split_unquoted() {
         split_ok(&[
-            (r#"\\|\\&\\;"#, &[r#"\|\&\;"#]),
-            (r#"\\<\\>"#, &[r#"\<\>"#]),
-            (r#"\\(\\)"#, &[r#"\(\)"#]),
-            (r#"\$"#, &[r#"$"#]),
+            (r"\\|\\&\\;", &[r"\|\&\;"]),
+            (r"\\<\\>", &[r"\<\>"]),
+            (r"\\(\\)", &[r"\(\)"]),
+            (r"\$", &[r"$"]),
             (r#"\""#, &[r#"""#]),
-            (r#"\'"#, &[r#"'"#]),
+            (r"\'", &[r"'"]),
             ("\\\n", &[]),
             (" \\\n \n", &[]),
             ("a\nb\nc", &["a", "b", "c"]),
@@ -1179,7 +1180,7 @@ mod tests_split_iterator {
             Err(ParseError::InvalidSequenceBackslashXInMinusS { pos: 2, c: 'a' })
         );
         assert_eq!(
-            split(r#"\🦉"#),
+            split(r"\🦉"),
             Err(ParseError::InvalidSequenceBackslashXInMinusS {
                 pos: 1,
                 c: '\u{FFFD}'
@@ -1190,9 +1191,9 @@ mod tests_split_iterator {
     #[test]
     fn split_comments() {
         split_ok(&[
-            (r#" x # comment "#, &["x"]),
-            (r#" w1#w2 "#, &["w1#w2"]),
-            (r#"'not really a # comment'"#, &["not really a # comment"]),
+            (r" x # comment ", &["x"]),
+            (r" w1#w2 ", &["w1#w2"]),
+            (r"'not really a # comment'", &["not really a # comment"]),
             (" a # very long comment \n b # another comment", &["a", "b"]),
         ]);
     }

tests/by-util/test_id.rs

@@ -16,11 +16,12 @@ fn test_invalid_arg() {
 
 #[test]
 #[cfg(unix)]
+#[allow(unused_mut)]
 fn test_id_no_specified_user() {
     let ts = TestScenario::new(util_name!());
     let result = ts.ucmd().run();
     let exp_result = unwrap_or_return!(expected_result(&ts, &[]));
-    let mut _exp_stdout = exp_result.stdout_str().to_string();
+    let mut exp_stdout = exp_result.stdout_str().to_string();
 
     #[cfg(not(feature = "feat_selinux"))]
     {
@@ -29,12 +30,12 @@ fn test_id_no_specified_user() {
         // uid=1001(runner) gid=121(docker) groups=121(docker),4(adm),101(systemd-journal) \
         // context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
         if let Some(context_offset) = exp_result.stdout_str().find(" context=") {
-            _exp_stdout.replace_range(context_offset.._exp_stdout.len() - 1, "");
+            exp_stdout.replace_range(context_offset..exp_stdout.len() - 1, "");
         }
     }
 
     result
-        .stdout_is(_exp_stdout)
+        .stdout_is(exp_stdout)
         .stderr_is(exp_result.stderr_str())
         .code_is(exp_result.code());
 }

tests/by-util/test_kill.rs

@@ -98,7 +98,7 @@ fn test_kill_table_lists_all_vertically() {
     let signals = command
         .stdout_str()
         .split('\n')
-        .flat_map(|line| line.trim().split(' ').nth(1))
+        .filter_map(|line| line.trim().split(' ').nth(1))
         .collect::<Vec<&str>>();
 
     assert!(signals.contains(&"KILL"));

tests/by-util/test_ln.rs

@@ -2,6 +2,8 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
+#![allow(clippy::similar_names)]
+
 use crate::common::util::TestScenario;
 use std::path::PathBuf;
 

tests/by-util/test_ls.rs

@@ -3,6 +3,11 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 // spell-checker:ignore (words) READMECAREFULLY birthtime doesntexist oneline somebackup lrwx somefile somegroup somehiddenbackup somehiddenfile tabsize aaaaaaaa bbbb cccc dddddddd ncccc neee naaaaa nbcdef nfffff dired subdired tmpfs mdir COLORTERM mexe bcdef mfoo
+#![allow(
+    clippy::similar_names,
+    clippy::too_many_lines,
+    clippy::cast_possible_truncation
+)]
 
 #[cfg(any(unix, feature = "feat_selinux"))]
 use crate::common::util::expected_result;
@@ -160,7 +165,7 @@ fn get_filesystem_type(scene: &TestScenario, path: &Path) -> String {
     let output = cmd.succeeds();
     let stdout_str = String::from_utf8_lossy(output.stdout());
     println!("output of stat call ({cmd:?}):\n{stdout_str}");
-    let regex_str = r#"Filesystem\s+Type\s+.+[\r\n]+([^\s]+)\s+(?<fstype>[^\s]+)\s+"#;
+    let regex_str = r"Filesystem\s+Type\s+.+[\r\n]+([^\s]+)\s+(?<fstype>[^\s]+)\s+";
     let regex = Regex::new(regex_str).unwrap();
     let m = regex.captures(&stdout_str).unwrap();
     let fstype = m["fstype"].to_owned();
@@ -1150,6 +1155,7 @@ fn test_ls_long_padding_of_size_column_with_multiple_files() {
 #[cfg(all(feature = "ln", feature = "mkdir", feature = "touch"))]
 #[test]
 #[cfg(all(feature = "ln", feature = "mkdir", feature = "touch"))]
+#[allow(clippy::items_after_statements)]
 fn test_ls_long_symlink_color() {
     // If you break this test after breaking mkdir, touch, or ln, do not be alarmed!
     // This test is made for ls, but it attempts to run those utils in the process.
@@ -1378,7 +1384,7 @@ fn test_ls_long_symlink_color() {
 
 /// This test is for "ls -l --color=auto|--color=always"
 /// We use "--color=always" as the colors are the same regardless of the color option being "auto" or "always"
-/// tests whether the specific color of the target and the dangling_symlink are equal and checks
+/// tests whether the specific color of the target and the `dangling_symlink` are equal and checks
 /// whether checks whether ls outputs the correct path for the symlink and the file it points to and applies the color code to it.
 #[test]
 fn test_ls_long_dangling_symlink_color() {

tests/by-util/test_mkdir.rs

@@ -2,6 +2,8 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
+#![allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
+
 use crate::common::util::TestScenario;
 #[cfg(not(windows))]
 use libc::mode_t;

tests/by-util/test_od.rs

@@ -560,8 +560,8 @@ fn test_dec_offset() {
 
 #[test]
 fn test_no_offset() {
-    let input = [0u8; 31];
     const LINE: &str = " 00000000 00000000 00000000 00000000\n";
+    let input = [0u8; 31];
     let expected_output = [LINE, LINE, LINE, LINE].join("");
 
     new_ucmd!()

tests/by-util/test_paste.rs

@@ -167,9 +167,9 @@ fn test_delimiter_list_ending_with_escaped_backslash() {
     for d in ["-d", "--delimiters"] {
         let (at, mut ucmd) = at_and_ucmd!();
         let mut ins = vec![];
-        for (i, _in) in ["a\n", "b\n"].iter().enumerate() {
+        for (i, one_in) in ["a\n", "b\n"].iter().enumerate() {
             let file = format!("in{}", i);
-            at.write(&file, _in);
+            at.write(&file, one_in);
             ins.push(file);
         }
         ucmd.args(&[d, "\\\\"])
@@ -198,9 +198,9 @@ fn test_data() {
     for example in EXAMPLE_DATA {
         let (at, mut ucmd) = at_and_ucmd!();
         let mut ins = vec![];
-        for (i, _in) in example.ins.iter().enumerate() {
+        for (i, one_in) in example.ins.iter().enumerate() {
             let file = format!("in{i}");
-            at.write(&file, _in);
+            at.write(&file, one_in);
             ins.push(file);
         }
         println!("{}", example.name);

tests/by-util/test_rm.rs

@@ -2,6 +2,8 @@
 //
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
+#![allow(clippy::stable_sort_primitive)]
+
 use std::process::Stdio;
 
 use crate::common::util::TestScenario;

tests/by-util/test_shuf.rs

@@ -106,7 +106,7 @@ fn test_very_large_range() {
         .collect();
     assert_eq!(result_seq.len(), num_samples, "Miscounted output length!");
     assert!(
-        result_seq.iter().all(|x| (0..=1234567890).contains(x)),
+        result_seq.iter().all(|x| (0..=1_234_567_890).contains(x)),
         "Output includes element not from range: {}",
         result.stdout_str()
     );
@@ -132,7 +132,7 @@ fn test_very_large_range_offset() {
     assert!(
         result_seq
             .iter()
-            .all(|x| (1234567890..=2147483647).contains(x)),
+            .all(|x| (1_234_567_890..=2_147_483_647).contains(x)),
         "Output includes element not from range: {}",
         result.stdout_str()
     );
@@ -234,7 +234,13 @@ fn test_range_permute_no_overflow_0_max() {
 #[test]
 fn test_very_high_range_full() {
     let input_seq = vec![
-        2147483641, 2147483642, 2147483643, 2147483644, 2147483645, 2147483646, 2147483647,
+        2_147_483_641,
+        2_147_483_642,
+        2_147_483_643,
+        2_147_483_644,
+        2_147_483_645,
+        2_147_483_646,
+        2_147_483_647,
     ];
     let result = new_ucmd!().arg("-i2147483641-2147483647").succeeds();
     result.no_stderr();
@@ -320,7 +326,7 @@ fn test_echo_multi() {
         .stdout_str()
         .split('\n')
         .filter(|x| !x.is_empty())
-        .map(|x| x.into())
+        .map(std::convert::Into::into)
         .collect();
     result_seq.sort_unstable();
     assert_eq!(result_seq, ["a", "b", "c"], "Output is not a permutation");
@@ -335,7 +341,7 @@ fn test_echo_postfix() {
         .stdout_str()
         .split('\n')
         .filter(|x| !x.is_empty())
-        .map(|x| x.into())
+        .map(std::convert::Into::into)
         .collect();
     result_seq.sort_unstable();
     assert_eq!(result_seq, ["a", "b", "c"], "Output is not a permutation");