From babda9037c16e3224416314806baa1cf2ce96e71 Mon Sep 17 00:00:00 2001
From: Sven van Heugten <sven@memcmp.org>
Date: Thu, 5 Mar 2026 20:15:19 +0100
Subject: [PATCH] Add a test where only a part of the line is replaced

---
 test/mechanicaldiff.bats | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/test/mechanicaldiff.bats b/test/mechanicaldiff.bats
index b00f234..ed5bbd2 100755
--- a/test/mechanicaldiff.bats
+++ b/test/mechanicaldiff.bats
@@ -138,3 +138,19 @@ setup() {
   assert_success
   assert_output "$(cat "$BATS_TEST_TMPDIR/diff")"
 }
+
+@test "replaces a substring within a line" {
+  cat >"$BATS_TEST_TMPDIR/old" <<-'EOF'
+	prefix foo suffix
+	EOF
+  cat >"$BATS_TEST_TMPDIR/new" <<-'EOF'
+	prefix bar suffix
+	EOF
+
+  git diff --no-index "$BATS_TEST_TMPDIR/old" "$BATS_TEST_TMPDIR/new" \
+    >"$BATS_TEST_TMPDIR/diff" || true
+
+  run mechanicaldiff.py foo bar <"$BATS_TEST_TMPDIR/diff"
+  assert_success
+  assert_output "$(cat "$BATS_TEST_TMPDIR/diff")"
+}