1 files changed, 53 insertions, 0 deletions
diff --git a/library/std/tests/switch-stdout.rs b/library/std/tests/switch-stdout.rs
new file mode 100644
index 00000000000..2605664d289
--- /dev/null
+++ b/library/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");
+}