tests/util: Improve UChild. Cleanup redundant functions in util.rs.

A short summary of changes:

* Add some basic tests for UChild and the run methods.
* Try more often in a fixed interval to create the tempfile for CapturedOutput.
* Fix drop order of struct fields for better cleanup of temporary files/dirs.
* Mark UChild::wait_with_output and UChild::pipe_in_and_wait_with_output deprecated
* Make CapturedOutput private
* Panic in stdout_all, stdout_all_bytes etc. if output is not captured.
* Rename some methods, refactor, clean up, fix documentation, add try_... methods

tests/by-util/test_rm.rs

@@ -374,12 +374,12 @@ fn test_rm_descend_directory() {
     at.touch(file_2);
 
     let mut child = scene.ucmd().arg("-ri").arg("a").run_no_wait();
-    child.write_in(yes.as_bytes()).unwrap();
-    child.write_in(yes.as_bytes()).unwrap();
-    child.write_in(yes.as_bytes()).unwrap();
-    child.write_in(yes.as_bytes()).unwrap();
-    child.write_in(yes.as_bytes()).unwrap();
-    child.write_in(yes.as_bytes()).unwrap();
+    child.try_write_in(yes.as_bytes()).unwrap();
+    child.try_write_in(yes.as_bytes()).unwrap();
+    child.try_write_in(yes.as_bytes()).unwrap();
+    child.try_write_in(yes.as_bytes()).unwrap();
+    child.try_write_in(yes.as_bytes()).unwrap();
+    child.try_write_in(yes.as_bytes()).unwrap();
 
     child.wait().unwrap();
 
@@ -447,7 +447,7 @@ fn test_rm_prompts() {
 
     let mut child = scene.ucmd().arg("-ri").arg("a").run_no_wait();
     for _ in 0..9 {
-        child.write_in(yes.as_bytes()).unwrap();
+        child.try_write_in(yes.as_bytes()).unwrap();
     }
 
     let result = child.wait().unwrap();
@@ -487,7 +487,7 @@ fn test_rm_force_prompts_order() {
 
     // This should cause rm to prompt to remove regular empty file
     let mut child = scene.ucmd().arg("-fi").arg(empty_file).run_no_wait();
-    child.write_in(yes.as_bytes()).unwrap();
+    child.try_write_in(yes.as_bytes()).unwrap();
 
     let result = child.wait().unwrap();
     let string_output = result.stderr_str();

tests/by-util/test_tail.rs

@@ -512,7 +512,7 @@ fn test_follow_non_utf8_bytes() {
         .run_no_wait();
 
     child
-        .make_assertion_with_delay(100)
+        .make_assertion_with_delay(500)
         .is_alive()
         .with_current_output()
         .stdout_only_fixture("foobar_single_default.expected");
@@ -712,7 +712,7 @@ fn test_follow_with_pid() {
         .run_no_wait();
 
     child
-        .make_assertion_with_delay(100)
+        .make_assertion_with_delay(500)
         .is_alive()
         .with_current_output()
         .stdout_only_fixture("foobar_follow_multiple.expected");
@@ -1392,9 +1392,8 @@ fn test_retry5() {
         at.mkdir(missing);
         p.delay(delay);
 
-        p.make_assertion().is_not_alive();
-        p.kill()
-            .make_assertion()
+        p.make_assertion()
+            .is_not_alive()
             .with_all_output()
             .stderr_only(expected_stderr)
             .failure();
@@ -1895,9 +1894,8 @@ fn test_follow_name_remove() {
         p.delay(delay);
 
         if i == 0 {
-            p.make_assertion().is_not_alive();
-            p.kill()
-                .make_assertion()
+            p.make_assertion()
+                .is_not_alive()
                 .with_all_output()
                 .stdout_is(&expected_stdout)
                 .stderr_is(&expected_stderr[i])
@@ -2299,9 +2297,8 @@ fn test_follow_name_move1() {
                 .stderr_is(&expected_stderr[i])
                 .stdout_is(&expected_stdout);
         } else {
-            p.make_assertion().is_not_alive();
-            p.kill()
-                .make_assertion()
+            p.make_assertion()
+                .is_not_alive()
                 .with_all_output()
                 .stderr_is(&expected_stderr[i])
                 .stdout_is(&expected_stdout)

tests/by-util/test_tee.rs

@@ -131,6 +131,8 @@ mod linux_only {
 
     fn run_tee(proc: &mut UCommand) -> (String, Output) {
         let content = (1..=100000).map(|x| format!("{}\n", x)).collect::<String>();
+
+        #[allow(deprecated)]
         let output = proc
             .run_no_wait()
             .pipe_in_and_wait_with_output(content.as_bytes());

tests/by-util/test_yes.rs

@@ -21,6 +21,8 @@ fn run(args: &[&str], expected: &[u8]) {
     let mut child = cmd.args(args).set_stdout(Stdio::piped()).run_no_wait();
     let buf = child.stdout_exact_bytes(expected.len());
     child.close_stdout();
+
+    #[allow(deprecated)]
     check_termination(&child.wait_with_output().unwrap().status);
     assert_eq!(buf.as_slice(), expected);
 }