Debian runs tests with stdin/stdout/stderr not connected to terminals, so testing against
the users terminal doesn't work, we instead create a pseudo terminal specifically to use
for testing.
Index: terminal-size/src/unix.rs
===================================================================
--- terminal-size.orig/src/unix.rs
+++ terminal-size/src/unix.rs
@@ -42,6 +42,29 @@ fn compare_with_stty() {
     use std::process::Command;
     use std::process::Stdio;
 
+    //in debian the tests run without a terminal, create one for testing
+    let slavename;
+    let slavefd;
+    unsafe {
+        use libc::{posix_openpt,O_RDWR,O_NOCTTY,grantpt,unlockpt,ptsname_r,winsize,ioctl,TIOCSWINSZ,open,c_char};
+        use std::ffi::CStr;
+        let masterfd = posix_openpt(O_RDWR | O_NOCTTY);
+        if masterfd < 0 {panic!("posix_openpt failed");}
+        if grantpt(masterfd) < 0 {panic!("grantpt failed");}
+        if unlockpt(masterfd) < 0 {panic!("unlockpt failed");}
+        let mut slavenamearr:[c_char;1024] = [0;1024];
+        if ptsname_r(masterfd,slavenamearr.as_mut_ptr(),1024) != 0 {panic!("ptsname_r failed");}
+        slavename = CStr::from_ptr(slavenamearr.as_mut_ptr()).to_str().unwrap();
+        let ws = winsize {
+            ws_row: 123,
+            ws_col: 456,
+            ws_xpixel: 0,
+            ws_ypixel: 0,
+        };
+        if ioctl(masterfd,TIOCSWINSZ,&ws) != 0 {panic!("TIOCSWINSZ failed")}
+        slavefd = open(slavenamearr.as_mut_ptr(), O_RDWR|O_NOCTTY);
+    }
+
     let (rows, cols) = if cfg!(target_os = "illumos") {
         // illumos stty(1) does not accept a device argument, instead using
         // stdin unconditionally:
@@ -77,14 +100,14 @@ fn compare_with_stty() {
             Command::new("stty")
                 .arg("size")
                 .arg("-F")
-                .arg("/dev/stderr")
+                .arg(slavename)
                 .stderr(Stdio::inherit())
                 .output()
                 .unwrap()
         } else {
             Command::new("stty")
                 .arg("-f")
-                .arg("/dev/stderr")
+                .arg(slavename)
                 .arg("size")
                 .stderr(Stdio::inherit())
                 .output()
@@ -102,7 +125,7 @@ fn compare_with_stty() {
     };
     println!("{} {}", rows, cols);
 
-    if let Some((Width(w), Height(h))) = terminal_size() {
+    if let Some((Width(w), Height(h))) = terminal_size_using_fd(slavefd) {
         assert_eq!(rows, h);
         assert_eq!(cols, w);
     } else {
Index: terminal-size/Cargo.toml
===================================================================
--- terminal-size.orig/Cargo.toml
+++ terminal-size/Cargo.toml
@@ -31,6 +31,9 @@ repository = "https://github.com/eminenc
 version = "0.35.7"
 features = ["termios"]
 
+[target."cfg(not(windows))".dev-dependencies.libc]
+version = "0.2"
+
 [target."cfg(windows)".dependencies.windows-sys]
 version = "0.36.0"
 features = [