Finally create a working test-case for #119

Assisted-by: Cursor

Author: twaugh

tests/interdiff-color-context/run-test

@@ -2,48 +2,113 @@
 
 # This is an interdiff(1) testcase.
 # Test: --color option should not break context trimming
+#
+# The bug: When --color is passed to internal diff, ANSI escape codes
+# break trim_context()'s ability to detect and strip "unline" content.
+# This test verifies the bug is fixed by ensuring --color doesn't break interdiff.
 
 . ${top_srcdir-.}/tests/common.sh
 
-# Create test files
-cat << EOF > file
+# Create test files that will generate interdiff output
+cat << EOF > original.txt
 line1
 line2
 line3
+line4
+line5
+line6
+line7
+line8
+line9
 line10
-line11
-line12
 EOF
 
-# First patch
-cat << EOF > patch1
---- file
-+++ file
-@@ -1,3 +1,3 @@
+# Create patches that modify overlapping regions to force interdiff generation
+cat << EOF > patch1.patch
+--- original.txt
++++ version1.txt
+@@ -1,6 +1,6 @@
  line1
--line2
-+MODIFIED2
- line3
+ line2
+-line3
++MODIFIED3
+ line4
+ line5
+ line6
+@@ -7,4 +7,4 @@
+ line7
+ line8
+-line9
++MODIFIED9
+ line10
 EOF
 
-# Second patch
-cat << EOF > patch2
---- file
-+++ file
-@@ -4,3 +4,3 @@
- line10
--line11
-+MODIFIED11
- line12
+cat << EOF > patch2.patch
+--- original.txt
++++ version2.txt
+@@ -2,6 +2,6 @@
+ line2
+ line3
+ line4
+-line5
++CHANGED5
+ line6
+ line7
+@@ -8,3 +8,3 @@
+ line8
+ line9
+-line10
++CHANGED10
 EOF
 
-# Generate interdiff with --color=always
-${INTERDIFF} --color=always patch1 patch2 2>errors >result || { cat errors; exit 1; }
+# Test the key requirement: --color should not break interdiff functionality
+# The original bug would cause interdiff to fail or produce incorrect output
+
+# First, test without color to establish baseline
+${INTERDIFF} patch1.patch patch2.patch >baseline.out 2>baseline.err
+baseline_exit=$?
+
+# Then test with --color=always
+${INTERDIFF} --color=always patch1.patch patch2.patch >color.out 2>color.err
+color_exit=$?
+
+# Key test 1: Both should have the same exit status
+if [ $baseline_exit -ne $color_exit ]; then
+    echo "ERROR: --color option changes interdiff exit status"
+    echo "Baseline exit: $baseline_exit, Color exit: $color_exit"
+    exit 1
+fi
+
+# Key test 2: If baseline succeeded, color version should also produce reasonable output
+if [ $baseline_exit -eq 0 ]; then
+    # Strip ANSI codes from color output for comparison
+    sed 's/\x1b\[[0-9;]*m//g' color.out > color_stripped.out
+
+    # The semantic content should be equivalent
+    if ! diff baseline.out color_stripped.out >/dev/null 2>&1; then
+        echo "ERROR: --color option changes interdiff semantic output"
+        echo "This indicates the color implementation interferes with diff processing"
+        echo
+        echo "=== Baseline output ==="
+        cat baseline.out
+        echo
+        echo "=== Color output (stripped) ==="
+        cat color_stripped.out
+        echo
+        echo "=== Difference ==="
+        diff baseline.out color_stripped.out || true
+        exit 1
+    fi
+fi
 
-# Apply patch1 to create the base state for testing the interdiff
-cp file file-with-patch1
-${PATCH} file-with-patch1 < patch1 || exit 1
+# Key test 3: The color output should not contain malformed content
+# Look for signs that trim_context() failed due to color codes
+if grep -E '^\x1b\[[0-9;]*m[!]+' color.out >/dev/null 2>&1; then
+    echo "ERROR: Found colored unline artifacts in output"
+    echo "This suggests trim_context() failed to strip artificial content"
+    echo "Raw output:"
+    cat -v color.out
+    exit 1
+fi
 
-# Test that the interdiff result can be applied cleanly
-cp file-with-patch1 file-test
-${PATCH} file-test < result || exit 1
+echo "SUCCESS: --color option does not break interdiff context trimming"