From 6ce077d4c1669c5cb092fd28e24bd30c93a004c4 Mon Sep 17 00:00:00 2001
From: Martin Paulsen <43757366+georgepaulsen@users.noreply.github.com>
Date: Wed, 31 Dec 2025 11:57:05 -0500
Subject: [PATCH 1/2] Check for three-string comparison in test

---
 src/uu/test/src/parser.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/uu/test/src/parser.rs b/src/uu/test/src/parser.rs
index 167bf77023a..c1c06e4c581 100644
--- a/src/uu/test/src/parser.rs
+++ b/src/uu/test/src/parser.rs
@@ -188,7 +188,16 @@ impl Parser {
         match symbol {
             Symbol::LParen => self.lparen()?,
             Symbol::Bang => self.bang()?,
-            Symbol::UnaryOp(_) => self.uop(symbol),
+            Symbol::UnaryOp(_) => {
+                // Three-argument string comparison: `-f = a` means "-f" = "a", not file test
+                let is_string_cmp = matches!(self.peek(), Symbol::Op(Operator::String(_)))
+                    && !matches!(Symbol::new(self.tokens.clone().nth(1)), Symbol::None);
+                if is_string_cmp {
+                    self.literal(symbol.into_literal())?;
+                } else {
+                    self.uop(symbol);
+                }
+            }
             Symbol::None => self.stack.push(symbol),
             literal => self.literal(literal)?,
         }

From 7bece70d9a88f24c8c626b0df301caa0035efb55 Mon Sep 17 00:00:00 2001
From: Martin Paulsen <43757366+georgepaulsen@users.noreply.github.com>
Date: Wed, 31 Dec 2025 11:59:48 -0500
Subject: [PATCH 2/2] Add regression tests for unary operator in three-arg form

---
 tests/by-util/test_test.rs | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tests/by-util/test_test.rs b/tests/by-util/test_test.rs
index 4b5460cfd4a..21ea1893e99 100644
--- a/tests/by-util/test_test.rs
+++ b/tests/by-util/test_test.rs
@@ -1027,3 +1027,10 @@ fn test_string_lt_gt_operator() {
         .fails_with_code(1)
         .no_output();
 }
+
+#[test]
+fn test_unary_op_as_literal_in_three_arg_form() {
+    // `-f = a` is string comparison "-f" = "a", not file test
+    new_ucmd!().args(&["-f", "=", "a"]).fails_with_code(1);
+    new_ucmd!().args(&["-f", "=", "a", "-o", "b"]).succeeds();
+}