diff --git a/tests/by-util/test_seq.rs b/tests/by-util/test_seq.rs
index 1fae070f4..25b400864 100644
--- a/tests/by-util/test_seq.rs
+++ b/tests/by-util/test_seq.rs
@@ -4,7 +4,6 @@
 // file that was distributed with this source code.
 // spell-checker:ignore lmnop xlmnop
 use crate::common::util::TestScenario;
-use std::process::Stdio;
 
 #[test]
 fn test_invalid_arg() {
@@ -566,51 +565,52 @@ fn test_width_floats() {
         .stdout_only("09.0\n10.0\n");
 }
 
-// TODO This is duplicated from `test_yes.rs`; refactor them.
-/// Run `seq`, capture some of the output, close the pipe, and verify it.
-fn run(args: &[&str], expected: &[u8]) {
-    let mut cmd = new_ucmd!();
-    let mut child = cmd.args(args).set_stdout(Stdio::piped()).run_no_wait();
-    let buf = child.stdout_exact_bytes(expected.len());
-    child.close_stdout();
-    child.wait().unwrap().success();
-    assert_eq!(buf.as_slice(), expected);
-}
-
 #[test]
 fn test_neg_inf() {
-    run(&["--", "-inf", "0"], b"-inf\n-inf\n-inf\n");
+    new_ucmd!()
+        .args(&["--", "-inf", "0"])
+        .run_stdout_starts_with(b"-inf\n-inf\n-inf\n")
+        .success();
 }
 
 #[test]
 fn test_neg_infinity() {
-    run(&["--", "-infinity", "0"], b"-inf\n-inf\n-inf\n");
+    new_ucmd!()
+        .args(&["--", "-infinity", "0"])
+        .run_stdout_starts_with(b"-inf\n-inf\n-inf\n")
+        .success();
 }
 
 #[test]
 fn test_inf() {
-    run(&["inf"], b"1\n2\n3\n");
+    new_ucmd!()
+        .args(&["inf"])
+        .run_stdout_starts_with(b"1\n2\n3\n")
+        .success();
 }
 
 #[test]
 fn test_infinity() {
-    run(&["infinity"], b"1\n2\n3\n");
+    new_ucmd!()
+        .args(&["infinity"])
+        .run_stdout_starts_with(b"1\n2\n3\n")
+        .success();
 }
 
 #[test]
 fn test_inf_width() {
-    run(
-        &["-w", "1.000", "inf", "inf"],
-        b"1.000\n  inf\n  inf\n  inf\n",
-    );
+    new_ucmd!()
+        .args(&["-w", "1.000", "inf", "inf"])
+        .run_stdout_starts_with(b"1.000\n  inf\n  inf\n  inf\n")
+        .success();
 }
 
 #[test]
 fn test_neg_inf_width() {
-    run(
-        &["-w", "1.000", "-inf", "-inf"],
-        b"1.000\n -inf\n -inf\n -inf\n",
-    );
+    new_ucmd!()
+        .args(&["-w", "1.000", "-inf", "-inf"])
+        .run_stdout_starts_with(b"1.000\n -inf\n -inf\n -inf\n")
+        .success();
 }
 
 #[test]
diff --git a/tests/by-util/test_yes.rs b/tests/by-util/test_yes.rs
index 26a7b14ac..9f5f84ed8 100644
--- a/tests/by-util/test_yes.rs
+++ b/tests/by-util/test_yes.rs
@@ -3,7 +3,7 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 use std::ffi::OsStr;
-use std::process::{ExitStatus, Stdio};
+use std::process::ExitStatus;
 
 #[cfg(unix)]
 use std::os::unix::process::ExitStatusExt;
@@ -22,15 +22,10 @@ fn check_termination(result: ExitStatus) {
 
 const NO_ARGS: &[&str] = &[];
 
-/// Run `yes`, capture some of the output, close the pipe, and verify it.
+/// Run `yes`, capture some of the output, then check exit status.
 fn run(args: &[impl AsRef<OsStr>], expected: &[u8]) {
-    let mut cmd = new_ucmd!();
-    let mut child = cmd.args(args).set_stdout(Stdio::piped()).run_no_wait();
-    let buf = child.stdout_exact_bytes(expected.len());
-    child.close_stdout();
-
-    check_termination(child.wait().unwrap().exit_status());
-    assert_eq!(buf.as_slice(), expected);
+    let result = new_ucmd!().args(args).run_stdout_starts_with(expected);
+    check_termination(result.exit_status());
 }
 
 #[test]
diff --git a/tests/common/util.rs b/tests/common/util.rs
index d6352b993..ec332c046 100644
--- a/tests/common/util.rs
+++ b/tests/common/util.rs
@@ -1846,6 +1846,18 @@ impl UCommand {
         let tmpdir_path = self.tmpd.as_ref().unwrap().path();
         format!("{}/{file_rel_path}", tmpdir_path.to_str().unwrap())
     }
+
+    /// Runs the command, checks that the stdout starts with "expected",
+    /// then terminates the command.
+    #[track_caller]
+    pub fn run_stdout_starts_with(&mut self, expected: &[u8]) -> CmdResult {
+        let mut child = self.set_stdout(Stdio::piped()).run_no_wait();
+        let buf = child.stdout_exact_bytes(expected.len());
+        child.close_stdout();
+
+        assert_eq!(buf.as_slice(), expected);
+        child.wait().unwrap()
+    }
 }
 
 impl std::fmt::Display for UCommand {