Fix "coreutils manpage base64" bug

tests/by-util/test_base64.rs

@@ -185,3 +185,38 @@ cyBvdmVyIHRoZSBsYXp5IGRvZy4=
             // cSpell:enable
         );
 }
+
+// Prevent regression to:
+//
+// ❯ coreutils manpage base64 | rg --fixed-strings -- 'base32'
+// The data are encoded as described for the base32 alphabet in RFC 4648.
+// to the bytes of the formal base32 alphabet. Use \-\-ignore\-garbage
+// The data are encoded as described for the base32 alphabet in RFC 4648.
+// to the bytes of the formal base32 alphabet. Use \-\-ignore\-garbage
+#[test]
+fn test_manpage() {
+    use std::process::{Command, Stdio};
+
+    let test_scenario = TestScenario::new("");
+
+    let child = Command::new(test_scenario.bin_path)
+        .arg("manpage")
+        .arg("base64")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .unwrap();
+
+    let output = child.wait_with_output().unwrap();
+
+    assert_eq!(output.status.code().unwrap(), 0);
+
+    assert!(output.stderr.is_empty());
+
+    let stdout_str = std::str::from_utf8(&output.stdout).unwrap();
+
+    assert!(stdout_str.contains("base64 alphabet"));
+
+    assert!(!stdout_str.to_ascii_lowercase().contains("base32"));
+}