diff --git a/src/uucore/src/lib/features/proc_info.rs b/src/uucore/src/lib/features/proc_info.rs
index 8345e7e0921..d36f5d0100b 100644
--- a/src/uucore/src/lib/features/proc_info.rs
+++ b/src/uucore/src/lib/features/proc_info.rs
@@ -465,11 +465,16 @@ mod tests {
             .flat_map(Teletype::try_from)
             .collect::<HashSet<_>>();
 
-        assert_eq!(result.len(), 1);
-        assert_eq!(
-            pid_entry.tty(),
-            Vec::from_iter(result.into_iter()).first().unwrap().clone()
-        );
+        // In CI environments or when running without a terminal, there may be no TTY
+        if result.is_empty() {
+            assert_eq!(pid_entry.tty(), Teletype::Unknown);
+        } else {
+            assert_eq!(result.len(), 1);
+            assert_eq!(
+                pid_entry.tty(),
+                Vec::from_iter(result.into_iter()).first().unwrap().clone()
+            );
+        }
     }
 
     #[test]
diff --git a/src/uucore/src/lib/features/process.rs b/src/uucore/src/lib/features/process.rs
index 55e8c36482b..043d4850d9b 100644
--- a/src/uucore/src/lib/features/process.rs
+++ b/src/uucore/src/lib/features/process.rs
@@ -67,13 +67,11 @@ pub fn getpid() -> pid_t {
 /// so some system such as redox doesn't supported.
 #[cfg(not(target_os = "redox"))]
 pub fn getsid(pid: i32) -> Result<pid_t, Errno> {
-    unsafe {
-        let result = libc::getsid(pid);
-        if Errno::last() == Errno::UnknownErrno {
-            Ok(result)
-        } else {
-            Err(Errno::last())
-        }
+    let result = unsafe { libc::getsid(pid) };
+    if result == -1 {
+        Err(Errno::last())
+    } else {
+        Ok(result)
     }
 }
 
diff --git a/tests/by-util/test_dd.rs b/tests/by-util/test_dd.rs
index 3e53f9a59e5..03c5bceebd6 100644
--- a/tests/by-util/test_dd.rs
+++ b/tests/by-util/test_dd.rs
@@ -1655,6 +1655,8 @@ fn test_reading_partial_blocks_from_fifo() {
         .stdout(Stdio::piped())
         .stderr(Stdio::piped())
         .env("LC_ALL", "C")
+        .env("LANG", "C")
+        .env("LANGUAGE", "C")
         .spawn()
         .unwrap();
 
@@ -1700,6 +1702,8 @@ fn test_reading_partial_blocks_from_fifo_unbuffered() {
         .stdout(Stdio::piped())
         .stderr(Stdio::piped())
         .env("LC_ALL", "C")
+        .env("LANG", "C")
+        .env("LANGUAGE", "C")
         .spawn()
         .unwrap();
 
diff --git a/util/build-run-test-coverage-linux.sh b/util/build-run-test-coverage-linux.sh
index 9dcfefed25c..8aba215304c 100755
--- a/util/build-run-test-coverage-linux.sh
+++ b/util/build-run-test-coverage-linux.sh
@@ -28,6 +28,8 @@
 set -e
 # Treat unset variables as errors
 set -u
+# Ensure pipeline failures are caught (not just the last command's exit code)
+set -o pipefail
 # Print expanded commands to stdout before running them
 set -x
 
@@ -39,7 +41,12 @@ REPO_main_dir="$(dirname -- "${ME_dir}")"
 FEATURES_OPTION=${FEATURES_OPTION:-"--features=feat_os_unix"}
 COVERAGE_DIR=${COVERAGE_DIR:-"${REPO_main_dir}/coverage"}
 
-LLVM_PROFDATA="$(find "$(rustc --print sysroot)" -name llvm-profdata)"
+# Find llvm-profdata in the nightly toolchain (which is used for coverage builds)
+LLVM_PROFDATA="$(find "$(RUSTUP_TOOLCHAIN=nightly-gnu rustc --print sysroot)" -name llvm-profdata)"
+if [ -z "${LLVM_PROFDATA}" ]; then
+    echo "Error: llvm-profdata not found. Install it with: rustup +nightly-gnu component add llvm-tools"
+    exit 1
+fi
 
 PROFRAW_DIR="${COVERAGE_DIR}/traces"
 PROFDATA_DIR="${COVERAGE_DIR}/data"