Start testing how the MSYS env var is customized

Author: EliahKagan

tests/tools/src/lib.rs

@@ -872,6 +872,7 @@ impl<'a> Drop for Env<'a> {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::ffi::OsStr;
 
     #[test]
     fn parse_version() {
@@ -932,4 +933,44 @@ mod tests {
         assert_eq!(lines, Vec::<&str>::new(), "should be no config variables from files");
         assert_eq!(status, 0, "reading the config should succeed");
     }
+
+    #[test]
+    fn configure_command_msys() {
+        let temp = tempfile::TempDir::new().expect("can create temp dir");
+        let mut cmd = std::process::Command::new("not-actually-run");
+
+        let msys_option = configure_command(&mut cmd, &[], temp.path())
+            .get_envs()
+            .find(|(k, _)| *k == OsStr::new("MSYS"))
+            .expect("should customize MSYS variable")
+            .1
+            .expect("should set, not unset, MSYS variable")
+            .to_str()
+            .expect("valid UTF-8")
+            .trim_matches(' ');
+
+        assert_eq!(msys_option, "winsymlinks:nativestrict");
+    }
+
+    #[test]
+    fn configure_command_msys_extends() {
+        let old_msys = r"error_start:C:\gdb.exe";
+        let temp = tempfile::TempDir::new().expect("can create temp dir");
+        let mut cmd = std::process::Command::new("not-actually-run");
+        cmd.env("MSYS", old_msys);
+
+        let msys_options = configure_command(&mut cmd, &[], temp.path())
+            .get_envs()
+            .find(|(k, _)| *k == OsStr::new("MSYS"))
+            .expect("should customize MSYS variable")
+            .1
+            .expect("should set, not unset, MSYS variable")
+            .to_str()
+            .expect("valid UTF-8")
+            .split(' ') // Just spaces, not arbitrary whitespace.
+            .filter(|s| !s.is_empty())
+            .collect::<Vec<_>>();
+
+        assert_eq!(msys_options, vec![old_msys, "winsymlinks:nativestrict"]);
+    }
 }