From 059f7b212c3acb028b4e11eca7f40edf5dff154c Mon Sep 17 00:00:00 2001
From: Andy Li <1450947+andy1li@users.noreply.github.com>
Date: Fri, 6 Jun 2025 05:16:16 +0800
Subject: [PATCH 1/7] Add new test cases for complex patterns in stage
 alternation

---
 internal/stage_alternation.go | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/internal/stage_alternation.go b/internal/stage_alternation.go
index ab74d77..2a52ae4 100644
--- a/internal/stage_alternation.go
+++ b/internal/stage_alternation.go
@@ -11,16 +11,21 @@ func testAlternation(stageHarness *test_case_harness.TestCaseHarness) error {
 			Input:            "a cat",
 			ExpectedExitCode: 0,
 		},
-		{
-			Pattern:          "a (cat|dog) and (cat|dog)s",
-			Input:            "a dog and cats",
-			ExpectedExitCode: 0,
-		},
 		{
 			Pattern:          "a (cat|dog)",
 			Input:            "a cow",
 			ExpectedExitCode: 1,
 		},
+		{
+			Pattern:          "^((Buffalo|buffalo)[ ]?)+$",
+			Input:            "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo",
+			ExpectedExitCode: 0,
+		},
+		{
+			Pattern:          "^((W|w)ill(, | |'s )?)+$",
+			Input:            "Will, will Will will Will Will's will",
+			ExpectedExitCode: 0,
+		},
 	}
 
 	return RunTestCases(testCases, stageHarness)

From 55145d131e5a12c1e9beb289a5aadc5dc3535e7c Mon Sep 17 00:00:00 2001
From: Andy Li <1450947+andy1li@users.noreply.github.com>
Date: Fri, 6 Jun 2025 05:18:00 +0800
Subject: [PATCH 2/7] Add new test cases for complex patterns in stage
 backreferences

---
 internal/test_helpers/fixtures/alternation/success       | 9 ++++++---
 .../fixtures/backreferences_multiple/success             | 9 ++++++---
 .../test_helpers/fixtures/backreferences_nested/success  | 9 ++++++---
 .../test_helpers/fixtures/backreferences_single/success  | 9 ++++++---
 4 files changed, 24 insertions(+), 12 deletions(-)

diff --git a/internal/test_helpers/fixtures/alternation/success b/internal/test_helpers/fixtures/alternation/success
index e632809..0522897 100644
--- a/internal/test_helpers/fixtures/alternation/success
+++ b/internal/test_helpers/fixtures/alternation/success
@@ -2,11 +2,14 @@
 [stage-12] $ echo -n "a cat" | ./your_grep.sh -E "a (cat|dog)"
 [your_program] a cat
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "a dog and cats" | ./your_grep.sh -E "a (cat|dog) and (cat|dog)s"
-[your_program] a dog and cats
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
+[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[your_program] Will, will Will will Will Will's will
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_multiple/success b/internal/test_helpers/fixtures/backreferences_multiple/success
index 3eecd5e..71566da 100644
--- a/internal/test_helpers/fixtures/backreferences_multiple/success
+++ b/internal/test_helpers/fixtures/backreferences_multiple/success
@@ -84,11 +84,14 @@
 [stage-12] $ echo -n "a cat" | ./your_grep.sh -E "a (cat|dog)"
 [your_program] a cat
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "a dog and cats" | ./your_grep.sh -E "a (cat|dog) and (cat|dog)s"
-[your_program] a dog and cats
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
+[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[your_program] Will, will Will will Will Will's will
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_nested/success b/internal/test_helpers/fixtures/backreferences_nested/success
index 6948816..873b1c3 100644
--- a/internal/test_helpers/fixtures/backreferences_nested/success
+++ b/internal/test_helpers/fixtures/backreferences_nested/success
@@ -125,11 +125,14 @@
 [stage-12] $ echo -n "a cat" | ./your_grep.sh -E "a (cat|dog)"
 [your_program] a cat
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "a dog and cats" | ./your_grep.sh -E "a (cat|dog) and (cat|dog)s"
-[your_program] a dog and cats
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
+[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[your_program] Will, will Will will Will Will's will
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_single/success b/internal/test_helpers/fixtures/backreferences_single/success
index d2614ce..f368987 100644
--- a/internal/test_helpers/fixtures/backreferences_single/success
+++ b/internal/test_helpers/fixtures/backreferences_single/success
@@ -43,11 +43,14 @@
 [stage-12] $ echo -n "a cat" | ./your_grep.sh -E "a (cat|dog)"
 [your_program] a cat
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "a dog and cats" | ./your_grep.sh -E "a (cat|dog) and (cat|dog)s"
-[your_program] a dog and cats
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
+[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[your_program] Will, will Will will Will Will's will
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3

From 59dd45f62632a55045a0e5374018e7bb2f7fd774 Mon Sep 17 00:00:00 2001
From: Andy Li <1450947+andy1li@users.noreply.github.com>
Date: Fri, 6 Jun 2025 05:39:07 +0800
Subject: [PATCH 3/7] Update regex patterns in test cases for 'will' to be
 case-insensitive

---
 internal/stage_alternation.go                                  | 2 +-
 internal/test_helpers/fixtures/alternation/success             | 2 +-
 internal/test_helpers/fixtures/backreferences_multiple/success | 2 +-
 internal/test_helpers/fixtures/backreferences_nested/success   | 2 +-
 internal/test_helpers/fixtures/backreferences_single/success   | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/internal/stage_alternation.go b/internal/stage_alternation.go
index 2a52ae4..5f62a14 100644
--- a/internal/stage_alternation.go
+++ b/internal/stage_alternation.go
@@ -22,7 +22,7 @@ func testAlternation(stageHarness *test_case_harness.TestCaseHarness) error {
 			ExpectedExitCode: 0,
 		},
 		{
-			Pattern:          "^((W|w)ill(, | |'s )?)+$",
+			Pattern:          "^([Ww]ill(, | |'s )?)+$",
 			Input:            "Will, will Will will Will Will's will",
 			ExpectedExitCode: 0,
 		},
diff --git a/internal/test_helpers/fixtures/alternation/success b/internal/test_helpers/fixtures/alternation/success
index 0522897..86909cb 100644
--- a/internal/test_helpers/fixtures/alternation/success
+++ b/internal/test_helpers/fixtures/alternation/success
@@ -7,7 +7,7 @@
 [stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
 [your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
diff --git a/internal/test_helpers/fixtures/backreferences_multiple/success b/internal/test_helpers/fixtures/backreferences_multiple/success
index 71566da..35361fa 100644
--- a/internal/test_helpers/fixtures/backreferences_multiple/success
+++ b/internal/test_helpers/fixtures/backreferences_multiple/success
@@ -89,7 +89,7 @@
 [stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
 [your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
diff --git a/internal/test_helpers/fixtures/backreferences_nested/success b/internal/test_helpers/fixtures/backreferences_nested/success
index 873b1c3..4a441d6 100644
--- a/internal/test_helpers/fixtures/backreferences_nested/success
+++ b/internal/test_helpers/fixtures/backreferences_nested/success
@@ -130,7 +130,7 @@
 [stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
 [your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
diff --git a/internal/test_helpers/fixtures/backreferences_single/success b/internal/test_helpers/fixtures/backreferences_single/success
index f368987..6fc788b 100644
--- a/internal/test_helpers/fixtures/backreferences_single/success
+++ b/internal/test_helpers/fixtures/backreferences_single/success
@@ -48,7 +48,7 @@
 [stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
 [your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^((W|w)ill(, | |'s )?)+$"
+[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.

From 02e488065d0bc196eaf9ecc52e6d842dbb84f6f4 Mon Sep 17 00:00:00 2001
From: Andy Li <1450947+andy1li@users.noreply.github.com>
Date: Sat, 7 Jun 2025 04:15:31 +0800
Subject: [PATCH 4/7] Update test cases to use a simplified input for 'Buffalo'
 pattern matching

---
 internal/stage_alternation.go                                 | 2 +-
 internal/test_helpers/fixtures/alternation/success            | 4 ++--
 .../test_helpers/fixtures/backreferences_multiple/success     | 4 ++--
 internal/test_helpers/fixtures/backreferences_nested/success  | 4 ++--
 internal/test_helpers/fixtures/backreferences_single/success  | 4 ++--
 5 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/internal/stage_alternation.go b/internal/stage_alternation.go
index 5f62a14..ac9a4e4 100644
--- a/internal/stage_alternation.go
+++ b/internal/stage_alternation.go
@@ -18,7 +18,7 @@ func testAlternation(stageHarness *test_case_harness.TestCaseHarness) error {
 		},
 		{
 			Pattern:          "^((Buffalo|buffalo)[ ]?)+$",
-			Input:            "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo",
+			Input:            "Buffalo buffalo buffalo Buffalo buffalo",
 			ExpectedExitCode: 0,
 		},
 		{
diff --git a/internal/test_helpers/fixtures/alternation/success b/internal/test_helpers/fixtures/alternation/success
index 86909cb..a2fe85b 100644
--- a/internal/test_helpers/fixtures/alternation/success
+++ b/internal/test_helpers/fixtures/alternation/success
@@ -4,8 +4,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
diff --git a/internal/test_helpers/fixtures/backreferences_multiple/success b/internal/test_helpers/fixtures/backreferences_multiple/success
index 35361fa..a4981cb 100644
--- a/internal/test_helpers/fixtures/backreferences_multiple/success
+++ b/internal/test_helpers/fixtures/backreferences_multiple/success
@@ -86,8 +86,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
diff --git a/internal/test_helpers/fixtures/backreferences_nested/success b/internal/test_helpers/fixtures/backreferences_nested/success
index 4a441d6..5361b7a 100644
--- a/internal/test_helpers/fixtures/backreferences_nested/success
+++ b/internal/test_helpers/fixtures/backreferences_nested/success
@@ -127,8 +127,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
diff --git a/internal/test_helpers/fixtures/backreferences_single/success b/internal/test_helpers/fixtures/backreferences_single/success
index 6fc788b..3f28051 100644
--- a/internal/test_helpers/fixtures/backreferences_single/success
+++ b/internal/test_helpers/fixtures/backreferences_single/success
@@ -45,8 +45,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
+[your_program] Buffalo buffalo buffalo Buffalo buffalo
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will

From 83fb4138714df67548bab837c26862a5ea72ce1e Mon Sep 17 00:00:00 2001
From: Andy Li <1450947+andy1li@users.noreply.github.com>
Date: Sat, 7 Jun 2025 04:58:10 +0800
Subject: [PATCH 5/7] Update test cases to replace 'Buffalo' pattern with a new
 regex for counting animals

---
 internal/stage_alternation.go                                 | 4 ++--
 internal/test_helpers/fixtures/alternation/success            | 4 ++--
 .../test_helpers/fixtures/backreferences_multiple/success     | 4 ++--
 internal/test_helpers/fixtures/backreferences_nested/success  | 4 ++--
 internal/test_helpers/fixtures/backreferences_single/success  | 4 ++--
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/internal/stage_alternation.go b/internal/stage_alternation.go
index ac9a4e4..22f9b83 100644
--- a/internal/stage_alternation.go
+++ b/internal/stage_alternation.go
@@ -17,8 +17,8 @@ func testAlternation(stageHarness *test_case_harness.TestCaseHarness) error {
 			ExpectedExitCode: 1,
 		},
 		{
-			Pattern:          "^((Buffalo|buffalo)[ ]?)+$",
-			Input:            "Buffalo buffalo buffalo Buffalo buffalo",
+			Pattern:          "^I see (\\d (cat|dog|cow)s?(, | and )?)+$",
+			Input:            "I see 1 cat, 2 dogs and 3 cows",
 			ExpectedExitCode: 0,
 		},
 		{
diff --git a/internal/test_helpers/fixtures/alternation/success b/internal/test_helpers/fixtures/alternation/success
index a2fe85b..49657b5 100644
--- a/internal/test_helpers/fixtures/alternation/success
+++ b/internal/test_helpers/fixtures/alternation/success
@@ -4,8 +4,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
+[your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
diff --git a/internal/test_helpers/fixtures/backreferences_multiple/success b/internal/test_helpers/fixtures/backreferences_multiple/success
index a4981cb..98b5974 100644
--- a/internal/test_helpers/fixtures/backreferences_multiple/success
+++ b/internal/test_helpers/fixtures/backreferences_multiple/success
@@ -86,8 +86,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
+[your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
diff --git a/internal/test_helpers/fixtures/backreferences_nested/success b/internal/test_helpers/fixtures/backreferences_nested/success
index 5361b7a..48e1746 100644
--- a/internal/test_helpers/fixtures/backreferences_nested/success
+++ b/internal/test_helpers/fixtures/backreferences_nested/success
@@ -127,8 +127,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
+[your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
diff --git a/internal/test_helpers/fixtures/backreferences_single/success b/internal/test_helpers/fixtures/backreferences_single/success
index 3f28051..3c4042b 100644
--- a/internal/test_helpers/fixtures/backreferences_single/success
+++ b/internal/test_helpers/fixtures/backreferences_single/success
@@ -45,8 +45,8 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Buffalo buffalo buffalo Buffalo buffalo" | ./your_grep.sh -E "^((Buffalo|buffalo)[ ]?)+$"
-[your_program] Buffalo buffalo buffalo Buffalo buffalo
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
+[your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will

From 364abe46d0a505f6f17f80b686341f5e664b9e37 Mon Sep 17 00:00:00 2001
From: Andy Li <1450947+andy1li@users.noreply.github.com>
Date: Sat, 7 Jun 2025 04:58:10 +0800
Subject: [PATCH 6/7] Update test cases to replace 'Buffalo' pattern with a new
 regex for counting animals

---
 internal/stage_alternation.go                             | 8 ++++----
 internal/test_helpers/fixtures/alternation/success        | 6 +++---
 .../test_helpers/fixtures/backreferences_multiple/success | 6 +++---
 .../test_helpers/fixtures/backreferences_nested/success   | 6 +++---
 .../test_helpers/fixtures/backreferences_single/success   | 6 +++---
 5 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/internal/stage_alternation.go b/internal/stage_alternation.go
index 22f9b83..bbd0eec 100644
--- a/internal/stage_alternation.go
+++ b/internal/stage_alternation.go
@@ -17,13 +17,13 @@ func testAlternation(stageHarness *test_case_harness.TestCaseHarness) error {
 			ExpectedExitCode: 1,
 		},
 		{
-			Pattern:          "^I see (\\d (cat|dog|cow)s?(, | and )?)+$",
-			Input:            "I see 1 cat, 2 dogs and 3 cows",
+			Pattern:          "^([Ww]ill(, | |'s )?)+$",
+			Input:            "Will, will Will will Will Will's will",
 			ExpectedExitCode: 0,
 		},
 		{
-			Pattern:          "^([Ww]ill(, | |'s )?)+$",
-			Input:            "Will, will Will will Will Will's will",
+			Pattern:          "^I see (\\d (cat|dog|cow)s?(, | and )?)+$",
+			Input:            "I see 1 cat, 2 dogs and 3 cows",
 			ExpectedExitCode: 0,
 		},
 	}
diff --git a/internal/test_helpers/fixtures/alternation/success b/internal/test_helpers/fixtures/alternation/success
index 49657b5..1f79627 100644
--- a/internal/test_helpers/fixtures/alternation/success
+++ b/internal/test_helpers/fixtures/alternation/success
@@ -4,12 +4,12 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
-[your_program] I see 1 cat, 2 dogs and 3 cows
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
+[your_program] I see 1 cat, 2 dogs and 3 cows
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_multiple/success b/internal/test_helpers/fixtures/backreferences_multiple/success
index 98b5974..ed82daf 100644
--- a/internal/test_helpers/fixtures/backreferences_multiple/success
+++ b/internal/test_helpers/fixtures/backreferences_multiple/success
@@ -86,12 +86,12 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
-[your_program] I see 1 cat, 2 dogs and 3 cows
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
+[your_program] I see 1 cat, 2 dogs and 3 cows
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_nested/success b/internal/test_helpers/fixtures/backreferences_nested/success
index 48e1746..26b80a3 100644
--- a/internal/test_helpers/fixtures/backreferences_nested/success
+++ b/internal/test_helpers/fixtures/backreferences_nested/success
@@ -127,12 +127,12 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
-[your_program] I see 1 cat, 2 dogs and 3 cows
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
+[your_program] I see 1 cat, 2 dogs and 3 cows
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_single/success b/internal/test_helpers/fixtures/backreferences_single/success
index 3c4042b..26a5f52 100644
--- a/internal/test_helpers/fixtures/backreferences_single/success
+++ b/internal/test_helpers/fixtures/backreferences_single/success
@@ -45,12 +45,12 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "I see (\d (cat|dog|cow)s?(, | and )?)+"
-[your_program] I see 1 cat, 2 dogs and 3 cows
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
 [your_program] Will, will Will will Will Will's will
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
+[your_program] I see 1 cat, 2 dogs and 3 cows
+[stage-12] ✓ Received exit code 0.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3

From f0b0d3a45fa4f584bd9e377740b78aa72759cfb0 Mon Sep 17 00:00:00 2001
From: Andy Li <1450947+andy1li@users.noreply.github.com>
Date: Sat, 7 Jun 2025 05:11:02 +0800
Subject: [PATCH 7/7] Update test cases to modify regex patterns for animal
 counting and adjust expected exit codes

---
 internal/stage_alternation.go                             | 8 ++++----
 internal/test_helpers/fixtures/alternation/success        | 5 ++---
 .../test_helpers/fixtures/backreferences_multiple/success | 5 ++---
 .../test_helpers/fixtures/backreferences_nested/success   | 5 ++---
 .../test_helpers/fixtures/backreferences_single/success   | 5 ++---
 5 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/internal/stage_alternation.go b/internal/stage_alternation.go
index bbd0eec..508c5ae 100644
--- a/internal/stage_alternation.go
+++ b/internal/stage_alternation.go
@@ -17,14 +17,14 @@ func testAlternation(stageHarness *test_case_harness.TestCaseHarness) error {
 			ExpectedExitCode: 1,
 		},
 		{
-			Pattern:          "^([Ww]ill(, | |'s )?)+$",
-			Input:            "Will, will Will will Will Will's will",
+			Pattern:          "^I see (\\d (cat|dog|cow)s?(, | and )?)+$",
+			Input:            "I see 1 cat, 2 dogs and 3 cows",
 			ExpectedExitCode: 0,
 		},
 		{
-			Pattern:          "^I see (\\d (cat|dog|cow)s?(, | and )?)+$",
+			Pattern:          "^I see (\\d (cat|dog|cow)(, | and )?)+$",
 			Input:            "I see 1 cat, 2 dogs and 3 cows",
-			ExpectedExitCode: 0,
+			ExpectedExitCode: 1,
 		},
 	}
 
diff --git a/internal/test_helpers/fixtures/alternation/success b/internal/test_helpers/fixtures/alternation/success
index 1f79627..d8a3ce0 100644
--- a/internal/test_helpers/fixtures/alternation/success
+++ b/internal/test_helpers/fixtures/alternation/success
@@ -4,12 +4,11 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
-[your_program] Will, will Will will Will Will's will
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
 [your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)(, | and )?)+$"
+[stage-12] ✓ Received exit code 1.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_multiple/success b/internal/test_helpers/fixtures/backreferences_multiple/success
index ed82daf..51e280e 100644
--- a/internal/test_helpers/fixtures/backreferences_multiple/success
+++ b/internal/test_helpers/fixtures/backreferences_multiple/success
@@ -86,12 +86,11 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
-[your_program] Will, will Will will Will Will's will
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
 [your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)(, | and )?)+$"
+[stage-12] ✓ Received exit code 1.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_nested/success b/internal/test_helpers/fixtures/backreferences_nested/success
index 26b80a3..ff68f1c 100644
--- a/internal/test_helpers/fixtures/backreferences_nested/success
+++ b/internal/test_helpers/fixtures/backreferences_nested/success
@@ -127,12 +127,11 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
-[your_program] Will, will Will will Will Will's will
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
 [your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)(, | and )?)+$"
+[stage-12] ✓ Received exit code 1.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3
diff --git a/internal/test_helpers/fixtures/backreferences_single/success b/internal/test_helpers/fixtures/backreferences_single/success
index 26a5f52..8d9c904 100644
--- a/internal/test_helpers/fixtures/backreferences_single/success
+++ b/internal/test_helpers/fixtures/backreferences_single/success
@@ -45,12 +45,11 @@
 [stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "a cow" | ./your_grep.sh -E "a (cat|dog)"
 [stage-12] ✓ Received exit code 1.
-[stage-12] $ echo -n "Will, will Will will Will Will's will" | ./your_grep.sh -E "^([Ww]ill(, | |'s )?)+$"
-[your_program] Will, will Will will Will Will's will
-[stage-12] ✓ Received exit code 0.
 [stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)s?(, | and )?)+$"
 [your_program] I see 1 cat, 2 dogs and 3 cows
 [stage-12] ✓ Received exit code 0.
+[stage-12] $ echo -n "I see 1 cat, 2 dogs and 3 cows" | ./your_grep.sh -E "^I see (\d (cat|dog|cow)(, | and )?)+$"
+[stage-12] ✓ Received exit code 1.
 [stage-12] Test passed.
 
 [stage-11] Running tests for Stage #11: zb3