Auto merge of rust-lang#112390 - MoskalykA:move-two-tests-from-library-to-tests, r=workingjubilee

Move two tests from `tests/ui/std` to `library/std/tests`

Hi, there,
This pull request comes from this issue (rust-lang#99417), sorry I made some mistakes creating the pull request, it's my first one.

Author: bors

std/tests/process_spawning.rs

@@ -0,0 +1,36 @@
+use std::env;
+use std::fs;
+use std::process;
+use std::str;
+
+mod common;
+
+#[test]
+fn issue_15149() {
+    // If we're the parent, copy our own binary to a new directory.
+    let my_path = env::current_exe().unwrap();
+
+    let temp = common::tmpdir();
+    let child_dir = temp.join("issue-15140-child");
+    fs::create_dir_all(&child_dir).unwrap();
+
+    let child_path = child_dir.join(&format!("mytest{}", env::consts::EXE_SUFFIX));
+    fs::copy(&my_path, &child_path).unwrap();
+
+    // Append the new directory to our own PATH.
+    let path = {
+        let mut paths: Vec<_> = env::split_paths(&env::var_os("PATH").unwrap()).collect();
+        paths.push(child_dir.to_path_buf());
+        env::join_paths(paths).unwrap()
+    };
+
+    let child_output =
+        process::Command::new("mytest").env("PATH", &path).arg("child").output().unwrap();
+
+    assert!(
+        child_output.status.success(),
+        "child assertion failed\n child stdout:\n {}\n child stderr:\n {}",
+        str::from_utf8(&child_output.stdout).unwrap(),
+        str::from_utf8(&child_output.stderr).unwrap()
+    );
+}

std/tests/switch-stdout.rs

@@ -0,0 +1,53 @@
+#[cfg(any(target_family = "unix", target_family = "windows"))]
+
+use std::fs::File;
+use std::io::{Read, Write};
+
+mod common;
+
+#[cfg(unix)]
+fn switch_stdout_to(file: File) {
+    use std::os::unix::prelude::*;
+
+    extern "C" {
+        fn dup2(old: i32, new: i32) -> i32;
+    }
+
+    unsafe {
+        assert_eq!(dup2(file.as_raw_fd(), 1), 1);
+    }
+}
+
+#[cfg(windows)]
+fn switch_stdout_to(file: File) {
+    use std::os::windows::prelude::*;
+
+    extern "system" {
+        fn SetStdHandle(nStdHandle: u32, handle: *mut u8) -> i32;
+    }
+
+    const STD_OUTPUT_HANDLE: u32 = (-11i32) as u32;
+
+    unsafe {
+        let rc = SetStdHandle(STD_OUTPUT_HANDLE, file.into_raw_handle() as *mut _);
+        assert!(rc != 0);
+    }
+}
+
+#[test]
+fn switch_stdout() {
+    let temp = common::tmpdir();
+    let path = temp.join("switch-stdout-output");
+    let f = File::create(&path).unwrap();
+
+    let mut stdout = std::io::stdout();
+    stdout.write(b"foo\n").unwrap();
+    stdout.flush().unwrap();
+    switch_stdout_to(f);
+    stdout.write(b"bar\n").unwrap();
+    stdout.flush().unwrap();
+
+    let mut contents = String::new();
+    File::open(&path).unwrap().read_to_string(&mut contents).unwrap();
+    assert_eq!(contents, "bar\n");
+}