From 78f8e1a3a016a39c06b3521f95dcb5aec4ac67b6 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:06:33 +0700
Subject: [PATCH 01/34] RED: test convert 1 to I

---
 test/roman_numerals_test.dart | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index ab73b3a..0dc4f81 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -1 +1,8 @@
-void main() {}
+import 'package:tdd_katas/roman_numerals.dart' as roman_numerals;
+import 'package:test/test.dart';
+
+void main() {
+  test('converts 1 to I', () {
+    expect(roman_numerals.integerToRoman(1), 'I');
+  });
+}

From 0faa1de47c9f97d7ac6d5fa24b9ebb0e53ea3023 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:08:35 +0700
Subject: [PATCH 02/34] GREEN: return hardcoded "I" for 1

---
 lib/roman_numerals.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 0cbc072..56b7b8e 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,3 +1,3 @@
 String integerToRoman(int number) {
-  throw UnimplementedError();
+  return 'I';
 }

From a4e668942781e58656c4d6849cd9d7e87d7acb41 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:10:32 +0700
Subject: [PATCH 03/34] RED: test converts 2 to II

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 0dc4f81..df86d16 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -5,4 +5,8 @@ void main() {
   test('converts 1 to I', () {
     expect(roman_numerals.integerToRoman(1), 'I');
   });
+
+  test('converts 2 to II', () {
+    expect(roman_numerals.integerToRoman(2), 'II');
+  });
 }

From 48b8967e0fd3102811ed794f17ba1f40e6fd9d7b Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:11:12 +0700
Subject: [PATCH 04/34] GREEN: return hardcoded "II" for 2

---
 lib/roman_numerals.dart | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 56b7b8e..af5a0c1 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,3 +1,10 @@
 String integerToRoman(int number) {
-  return 'I';
+  if (number == 1) {
+    return 'I';
+  }
+  if (number == 2) {
+    return 'II';
+  }
+
+  throw UnimplementedError('Conversion not implemented for $number');
 }

From 6f5b2ab2f5fe63852c6c04fa833dab948be47403 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:12:28 +0700
Subject: [PATCH 05/34] RED: test convert 3 to III

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index df86d16..c8f9f17 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -9,4 +9,8 @@ void main() {
   test('converts 2 to II', () {
     expect(roman_numerals.integerToRoman(2), 'II');
   });
+
+  test('converts 3 to III', () {
+    expect(roman_numerals.integerToRoman(3), 'III');
+  });
 }

From ba924edde7227b8e0a4f6e4da1daf1bf92ec5a13 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:14:06 +0700
Subject: [PATCH 06/34] GREEN: add simple logic to handle 1-3

---
 lib/roman_numerals.dart | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index af5a0c1..d41a455 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,10 +1,7 @@
 String integerToRoman(int number) {
-  if (number == 1) {
-    return 'I';
+  var result = '';
+  for (int i = 0; i < number; i++) {
+    result += 'I';
   }
-  if (number == 2) {
-    return 'II';
-  }
-
-  throw UnimplementedError('Conversion not implemented for $number');
+  return result;
 }

From 0de7f6708015b6de8952baadbb627c5c1609e7ca Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:17:06 +0700
Subject: [PATCH 07/34] RED: test convert 5 to V

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index c8f9f17..dd7fded 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -13,4 +13,8 @@ void main() {
   test('converts 3 to III', () {
     expect(roman_numerals.integerToRoman(3), 'III');
   });
+
+  test('converts 5 to V', () {
+    expect(roman_numerals.integerToRoman(5), 'V');
+  });
 }

From 1cfd2199ee32f8419a0ce2ed5efcfb5d1a2c5c5c Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:19:23 +0700
Subject: [PATCH 08/34] GREEN: return hardcoded "V" for 5

---
 lib/roman_numerals.dart | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index d41a455..ef9f436 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,6 +1,11 @@
 String integerToRoman(int number) {
   var result = '';
   for (int i = 0; i < number; i++) {
+    if (number == 5) {
+      result += 'V';
+      break;
+    }
+
     result += 'I';
   }
   return result;

From 87b7e7946239b33bded6f8ca109c150330b7f0e6 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:20:05 +0700
Subject: [PATCH 09/34] RED: test convert 4 to IV

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index dd7fded..324c4ea 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -17,4 +17,8 @@ void main() {
   test('converts 5 to V', () {
     expect(roman_numerals.integerToRoman(5), 'V');
   });
+
+  test('converts 4 to IV', () {
+    expect(roman_numerals.integerToRoman(4), 'IV');
+  });
 }

From 5c9962eb6102d4bd17915807188301bea62c0170 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:22:39 +0700
Subject: [PATCH 10/34] GREEN: return hardcoded "IV" for 4

---
 lib/roman_numerals.dart | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index ef9f436..a962a11 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -3,7 +3,12 @@ String integerToRoman(int number) {
   for (int i = 0; i < number; i++) {
     if (number == 5) {
       result += 'V';
-      break;
+      return result;
+    }
+
+    if (number == 4) {
+      result += 'IV';
+      return result;
     }
 
     result += 'I';

From c1a5ed7ed7dd018b055a12f96517cf2699704512 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:39:34 +0700
Subject: [PATCH 11/34] REFACTOR: extract logic and remove loop

---
 lib/roman_numerals.dart       | 26 +++++++++++++-------------
 test/roman_numerals_test.dart |  8 ++++----
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index a962a11..8bd07b5 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,17 +1,17 @@
 String integerToRoman(int number) {
-  var result = '';
-  for (int i = 0; i < number; i++) {
-    if (number == 5) {
-      result += 'V';
-      return result;
-    }
+  const romanSymbols = {5: 'V', 1: 'I'};
 
-    if (number == 4) {
-      result += 'IV';
-      return result;
-    }
-
-    result += 'I';
+  if (_isSubtractiveCase(number)) {
+    return romanSymbols[1]! + romanSymbols[5]!;
   }
-  return result;
+
+  if (_canRepeatSymbol(number)) {
+    return romanSymbols[1]! * number;
+  }
+
+  return romanSymbols[number] ?? '';
 }
+
+bool _isSubtractiveCase(int number) => number == 4;
+
+bool _canRepeatSymbol(int number) => number < 4;
diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 324c4ea..bc1732f 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -14,11 +14,11 @@ void main() {
     expect(roman_numerals.integerToRoman(3), 'III');
   });
 
-  test('converts 5 to V', () {
-    expect(roman_numerals.integerToRoman(5), 'V');
-  });
-
   test('converts 4 to IV', () {
     expect(roman_numerals.integerToRoman(4), 'IV');
   });
+
+  test('converts 5 to V', () {
+    expect(roman_numerals.integerToRoman(5), 'V');
+  });
 }

From dfa3b66ccb466a27709bfbbf289f61af84474cec Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:42:02 +0700
Subject: [PATCH 12/34] RED: test convert 6 to VI

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index bc1732f..f344ea0 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -21,4 +21,8 @@ void main() {
   test('converts 5 to V', () {
     expect(roman_numerals.integerToRoman(5), 'V');
   });
+
+  test('converts 6 to VI', () {
+    expect(roman_numerals.integerToRoman(6), 'VI');
+  });
 }

From 445ba862eefd668b9a323631e80da7eeefea8307 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:43:00 +0700
Subject: [PATCH 13/34] GREEN: add roman symbol for 6

---
 lib/roman_numerals.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 8bd07b5..75e27bc 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,5 @@
 String integerToRoman(int number) {
-  const romanSymbols = {5: 'V', 1: 'I'};
+  const romanSymbols = {6: 'VI', 5: 'V', 1: 'I'};
 
   if (_isSubtractiveCase(number)) {
     return romanSymbols[1]! + romanSymbols[5]!;

From 44845ed71b2f477d625f938af2432f4908ec72fd Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:43:57 +0700
Subject: [PATCH 14/34] RED: test convert 7 to VII

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index f344ea0..292247e 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -25,4 +25,8 @@ void main() {
   test('converts 6 to VI', () {
     expect(roman_numerals.integerToRoman(6), 'VI');
   });
+
+  test('converts 7 to VII', () {
+    expect(roman_numerals.integerToRoman(7), 'VII');
+  });
 }

From 6ad0556fcf5b606bc0cc386b3714b5b5ee918715 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:44:18 +0700
Subject: [PATCH 15/34] GREEN: add roman symbol for 7

---
 lib/roman_numerals.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 75e27bc..3476605 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,5 @@
 String integerToRoman(int number) {
-  const romanSymbols = {6: 'VI', 5: 'V', 1: 'I'};
+  const romanSymbols = {7: 'VII', 6: 'VI', 5: 'V', 1: 'I'};
 
   if (_isSubtractiveCase(number)) {
     return romanSymbols[1]! + romanSymbols[5]!;

From b5a216cceaee5983b6d70b0c26062348d80c1354 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:44:55 +0700
Subject: [PATCH 16/34] RED: test convert 8 to VIII

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 292247e..43f1869 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -29,4 +29,8 @@ void main() {
   test('converts 7 to VII', () {
     expect(roman_numerals.integerToRoman(7), 'VII');
   });
+
+  test('converts 8 to VIII', () {
+    expect(roman_numerals.integerToRoman(8), 'VIII');
+  });
 }

From f6d75f15e1d26a185396dc980434a657e9a8e42a Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:45:51 +0700
Subject: [PATCH 17/34] GREEN: add roman symbol for 8

---
 lib/roman_numerals.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 3476605..9ba01a9 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,5 @@
 String integerToRoman(int number) {
-  const romanSymbols = {7: 'VII', 6: 'VI', 5: 'V', 1: 'I'};
+  const romanSymbols = {8: 'VIII', 7: 'VII', 6: 'VI', 5: 'V', 1: 'I'};
 
   if (_isSubtractiveCase(number)) {
     return romanSymbols[1]! + romanSymbols[5]!;

From 0a87dc96cb8f16bb26ed15ca18f13b52aba2228a Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:48:59 +0700
Subject: [PATCH 18/34] RED: test convert 9 to IX

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 43f1869..5504e98 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -33,4 +33,8 @@ void main() {
   test('converts 8 to VIII', () {
     expect(roman_numerals.integerToRoman(8), 'VIII');
   });
+
+  test('converts 9 to IX', () {
+    expect(roman_numerals.integerToRoman(9), 'IX');
+  });
 }

From da8f7bbfb10057a36d8f203ccedc758212823f91 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:49:39 +0700
Subject: [PATCH 19/34] GREEN: add roman symbol for 9

---
 lib/roman_numerals.dart | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 9ba01a9..5c084ea 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,5 @@
 String integerToRoman(int number) {
-  const romanSymbols = {8: 'VIII', 7: 'VII', 6: 'VI', 5: 'V', 1: 'I'};
+  const romanSymbols = {9: 'IX', 8: 'VIII', 7: 'VII', 6: 'VI', 5: 'V', 1: 'I'};
 
   if (_isSubtractiveCase(number)) {
     return romanSymbols[1]! + romanSymbols[5]!;

From 2117e4c193b91e3e5fb9fbd1cc368531301f585e Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:50:33 +0700
Subject: [PATCH 20/34] RED: test convert 10 to X

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 5504e98..4bde3a0 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -37,4 +37,8 @@ void main() {
   test('converts 9 to IX', () {
     expect(roman_numerals.integerToRoman(9), 'IX');
   });
+
+  test('converts 10 to X', () {
+    expect(roman_numerals.integerToRoman(10), 'X');
+  });
 }

From 7eed3f8e2ace836ed7f88080d17bc80f852a6c74 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 08:50:50 +0700
Subject: [PATCH 21/34] GREEN: add roman symbol for 10

---
 lib/roman_numerals.dart | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 5c084ea..f4fbc57 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,13 @@
 String integerToRoman(int number) {
-  const romanSymbols = {9: 'IX', 8: 'VIII', 7: 'VII', 6: 'VI', 5: 'V', 1: 'I'};
+  const romanSymbols = {
+    10: 'X',
+    9: 'IX',
+    8: 'VIII',
+    7: 'VII',
+    6: 'VI',
+    5: 'V',
+    1: 'I',
+  };
 
   if (_isSubtractiveCase(number)) {
     return romanSymbols[1]! + romanSymbols[5]!;

From b12821147d95e606e665ddca68dc1168796be439 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:12:34 +0700
Subject: [PATCH 22/34] REFACTOR: apply DRY, remove  magic numbers, add
 `conversionRules` domain

---
 lib/roman_numerals.dart | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index f4fbc57..f4666c1 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,25 +1,15 @@
 String integerToRoman(int number) {
-  const romanSymbols = {
-    10: 'X',
-    9: 'IX',
-    8: 'VIII',
-    7: 'VII',
-    6: 'VI',
-    5: 'V',
-    1: 'I',
-  };
+  const conversionRules = [(10, 'X'), (9, 'IX'), (5, 'V'), (4, 'IV'), (1, 'I')];
 
-  if (_isSubtractiveCase(number)) {
-    return romanSymbols[1]! + romanSymbols[5]!;
+  final result = StringBuffer();
+  var remaining = number;
+
+  for (final (value, symbol) in conversionRules) {
+    while (remaining >= value) {
+      result.write(symbol);
+      remaining -= value;
+    }
   }
 
-  if (_canRepeatSymbol(number)) {
-    return romanSymbols[1]! * number;
-  }
-
-  return romanSymbols[number] ?? '';
+  return result.toString();
 }
-
-bool _isSubtractiveCase(int number) => number == 4;
-
-bool _canRepeatSymbol(int number) => number < 4;

From e411e38a314adb5ea8f518f16ebb56e8394be776 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:12:54 +0700
Subject: [PATCH 23/34] RED: test convert 40 to XL

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 4bde3a0..90d3e90 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -41,4 +41,8 @@ void main() {
   test('converts 10 to X', () {
     expect(roman_numerals.integerToRoman(10), 'X');
   });
+
+  test('converts 40 to XL', () {
+    expect(roman_numerals.integerToRoman(40), 'XL');
+  });
 }

From bef6a56d0621d8e5d131acb53fcef1c078d5449c Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:16:38 +0700
Subject: [PATCH 24/34] GREEN: add coversion rule for 40

---
 lib/roman_numerals.dart | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index f4666c1..abddc4d 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,12 @@
 String integerToRoman(int number) {
-  const conversionRules = [(10, 'X'), (9, 'IX'), (5, 'V'), (4, 'IV'), (1, 'I')];
+  const conversionRules = [
+    (40, 'XL'),
+    (10, 'X'),
+    (9, 'IX'),
+    (5, 'V'),
+    (4, 'IV'),
+    (1, 'I'),
+  ];
 
   final result = StringBuffer();
   var remaining = number;

From 44566369d0e8f8a7066bbc006f03f4637350a24a Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:18:11 +0700
Subject: [PATCH 25/34] RED: test convert 50 to L

---
 test/roman_numerals_test.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 90d3e90..da5dc7e 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -45,4 +45,8 @@ void main() {
   test('converts 40 to XL', () {
     expect(roman_numerals.integerToRoman(40), 'XL');
   });
+
+  test('converts 50 to L', () {
+    expect(roman_numerals.integerToRoman(50), 'L');
+  });
 }

From dc6728bea5446b028340b968e7a0682c2722efc4 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:18:47 +0700
Subject: [PATCH 26/34] GREEN: add conversion rule for 50

---
 lib/roman_numerals.dart | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index abddc4d..0697888 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,6 @@
 String integerToRoman(int number) {
   const conversionRules = [
+    (50, 'L'),
     (40, 'XL'),
     (10, 'X'),
     (9, 'IX'),

From 24cdceaa9254ceae0b3fa8d2a19eb12a553ec86b Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:20:39 +0700
Subject: [PATCH 27/34] RED: test convert 90 to XC and 100 to C

---
 test/roman_numerals_test.dart | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index da5dc7e..6cc7f75 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -49,4 +49,12 @@ void main() {
   test('converts 50 to L', () {
     expect(roman_numerals.integerToRoman(50), 'L');
   });
+
+  test('converts 90 to XC', () {
+    expect(roman_numerals.integerToRoman(90), 'XC');
+  });
+
+  test('converts 100 to C', () {
+    expect(roman_numerals.integerToRoman(100), 'C');
+  });
 }

From 1b0336edeb8c8a6d384d492dd85bd95a6247dbd2 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:21:10 +0700
Subject: [PATCH 28/34] GREEN: add convertion rules for 90 and 100

---
 lib/roman_numerals.dart | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 0697888..f2bb0d8 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,7 @@
 String integerToRoman(int number) {
   const conversionRules = [
+    (100, 'C'),
+    (90, 'XC'),
     (50, 'L'),
     (40, 'XL'),
     (10, 'X'),

From ccfc795ee0502939009ad4d5efa765ae87453f5b Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:24:03 +0700
Subject: [PATCH 29/34] RED: test convert 400 (CD), 500 (D), 900 (CM), 1000 (M)

---
 test/roman_numerals_test.dart | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 6cc7f75..36b02c1 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -46,6 +46,10 @@ void main() {
     expect(roman_numerals.integerToRoman(40), 'XL');
   });
 
+  test('converts 49 to XLIX', () {
+    expect(roman_numerals.integerToRoman(49), 'XLIX');
+  });
+
   test('converts 50 to L', () {
     expect(roman_numerals.integerToRoman(50), 'L');
   });
@@ -57,4 +61,20 @@ void main() {
   test('converts 100 to C', () {
     expect(roman_numerals.integerToRoman(100), 'C');
   });
+
+  test('converts 400 to CD', () {
+    expect(roman_numerals.integerToRoman(400), 'CD');
+  });
+
+  test('converts 500 to D', () {
+    expect(roman_numerals.integerToRoman(500), 'D');
+  });
+
+  test('converts 900 to CM', () {
+    expect(roman_numerals.integerToRoman(900), 'CM');
+  });
+
+  test('converts 1000 to M', () {
+    expect(roman_numerals.integerToRoman(1000), 'M');
+  });
 }

From 5bf2839e33b5687d98008c9b66cfdfff928a77ed Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:25:07 +0700
Subject: [PATCH 30/34] GREEN: add conversion rules for 400. 500. 900, and 1000

---
 lib/roman_numerals.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index f2bb0d8..cac6eb6 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,5 +1,9 @@
 String integerToRoman(int number) {
   const conversionRules = [
+    (1000, 'M'),
+    (900, 'CM'),
+    (500, 'D'),
+    (400, 'CD'),
     (100, 'C'),
     (90, 'XC'),
     (50, 'L'),

From 5dfc85fc2094e5052854044e76bdd268a5b44394 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:31:30 +0700
Subject: [PATCH 31/34] REFACTOR: organize tests into groups and add edge cases

---
 test/roman_numerals_test.dart | 134 ++++++++++++++++------------------
 1 file changed, 62 insertions(+), 72 deletions(-)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index 36b02c1..d9c8619 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -1,80 +1,70 @@
-import 'package:tdd_katas/roman_numerals.dart' as roman_numerals;
+import 'package:tdd_katas/roman_numerals.dart';
 import 'package:test/test.dart';
 
 void main() {
-  test('converts 1 to I', () {
-    expect(roman_numerals.integerToRoman(1), 'I');
-  });
+  group('Roman Numerals Conversion', () {
+    group('Basic Symbols', () {
+      test('smallest unit', () => expect(integerToRoman(1), 'I'));
+      test('five', () => expect(integerToRoman(5), 'V'));
+      test('ten', () => expect(integerToRoman(10), 'X'));
+      test('fifty', () => expect(integerToRoman(50), 'L'));
+      test('hundred', () => expect(integerToRoman(100), 'C'));
+      test('five hundred', () => expect(integerToRoman(500), 'D'));
+      test('thousand', () => expect(integerToRoman(1000), 'M'));
+    });
 
-  test('converts 2 to II', () {
-    expect(roman_numerals.integerToRoman(2), 'II');
-  });
+    group('Subtractive Notation', () {
+      test('four (one before five)', () => expect(integerToRoman(4), 'IV'));
+      test('nine (one before ten)', () => expect(integerToRoman(9), 'IX'));
+      test('forty (ten before fifty)', () => expect(integerToRoman(40), 'XL'));
+      test(
+        'ninety (ten before hundred)',
+        () => expect(integerToRoman(90), 'XC'),
+      );
+      test(
+        'four hundred (hundred before five hundred)',
+        () => expect(integerToRoman(400), 'CD'),
+      );
+      test(
+        'nine hundred (hundred before thousand)',
+        () => expect(integerToRoman(900), 'CM'),
+      );
+    });
 
-  test('converts 3 to III', () {
-    expect(roman_numerals.integerToRoman(3), 'III');
-  });
+    group('Additive Combinations', () {
+      test('two (repeated symbol)', () => expect(integerToRoman(2), 'II'));
+      test(
+        'three (maximum repetition)',
+        () => expect(integerToRoman(3), 'III'),
+      );
+      test('six (additive after five)', () => expect(integerToRoman(6), 'VI'));
+      test(
+        'twenty-seven (multiple symbols)',
+        () => expect(integerToRoman(27), 'XXVII'),
+      );
+    });
 
-  test('converts 4 to IV', () {
-    expect(roman_numerals.integerToRoman(4), 'IV');
-  });
-
-  test('converts 5 to V', () {
-    expect(roman_numerals.integerToRoman(5), 'V');
-  });
-
-  test('converts 6 to VI', () {
-    expect(roman_numerals.integerToRoman(6), 'VI');
-  });
-
-  test('converts 7 to VII', () {
-    expect(roman_numerals.integerToRoman(7), 'VII');
-  });
-
-  test('converts 8 to VIII', () {
-    expect(roman_numerals.integerToRoman(8), 'VIII');
-  });
-
-  test('converts 9 to IX', () {
-    expect(roman_numerals.integerToRoman(9), 'IX');
-  });
-
-  test('converts 10 to X', () {
-    expect(roman_numerals.integerToRoman(10), 'X');
-  });
-
-  test('converts 40 to XL', () {
-    expect(roman_numerals.integerToRoman(40), 'XL');
-  });
-
-  test('converts 49 to XLIX', () {
-    expect(roman_numerals.integerToRoman(49), 'XLIX');
-  });
-
-  test('converts 50 to L', () {
-    expect(roman_numerals.integerToRoman(50), 'L');
-  });
-
-  test('converts 90 to XC', () {
-    expect(roman_numerals.integerToRoman(90), 'XC');
-  });
-
-  test('converts 100 to C', () {
-    expect(roman_numerals.integerToRoman(100), 'C');
-  });
-
-  test('converts 400 to CD', () {
-    expect(roman_numerals.integerToRoman(400), 'CD');
-  });
-
-  test('converts 500 to D', () {
-    expect(roman_numerals.integerToRoman(500), 'D');
-  });
-
-  test('converts 900 to CM', () {
-    expect(roman_numerals.integerToRoman(900), 'CM');
-  });
-
-  test('converts 1000 to M', () {
-    expect(roman_numerals.integerToRoman(1000), 'M');
+    group('Complex Edge Cases', () {
+      test(
+        'forty-nine (combines subtractive symbols)',
+        () => expect(integerToRoman(49), 'XLIX'),
+      );
+      test(
+        'ninety-nine (maximum two-digit complexity)',
+        () => expect(integerToRoman(99), 'XCIX'),
+      );
+      test(
+        'four hundred forty-four (all subtractive positions)',
+        () => expect(integerToRoman(444), 'CDXLIV'),
+      );
+      test(
+        '1994 (year notation stress test)',
+        () => expect(integerToRoman(1994), 'MCMXCIV'),
+      );
+      test(
+        '3999 (maximum valid Roman numeral)',
+        () => expect(integerToRoman(3999), 'MMMCMXCIX'),
+      );
+    });
   });
 }

From 216aa72d39b0ca49f1f17eeb1ca3e986fa908f6e Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:33:44 +0700
Subject: [PATCH 32/34] RED: test roman numerals contraints

---
 test/roman_numerals_test.dart | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/test/roman_numerals_test.dart b/test/roman_numerals_test.dart
index d9c8619..831aa9c 100644
--- a/test/roman_numerals_test.dart
+++ b/test/roman_numerals_test.dart
@@ -66,5 +66,19 @@ void main() {
         () => expect(integerToRoman(3999), 'MMMCMXCIX'),
       );
     });
+
+    group('Error Handling', () {
+      test('rejects zero', () {
+        expect(() => integerToRoman(0), throwsArgumentError);
+      });
+
+      test('rejects negative numbers', () {
+        expect(() => integerToRoman(-5), throwsArgumentError);
+      });
+
+      test('rejects numbers above 3999', () {
+        expect(() => integerToRoman(4000), throwsArgumentError);
+      });
+    });
   });
 }

From 438221e2d76b10052975dc802e1bd5498d64c06a Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:34:43 +0700
Subject: [PATCH 33/34] GREEN: implement roman numerals contraints

---
 lib/roman_numerals.dart | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index cac6eb6..0490bcb 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -15,6 +15,10 @@ String integerToRoman(int number) {
     (1, 'I'),
   ];
 
+  if (number <= 0 || number > 3999) {
+    throw ArgumentError('Number must be between 1 and 3999');
+  }
+
   final result = StringBuffer();
   var remaining = number;
 

From 6e75926f7970e0e4d07e6a637e8a1fb9e6d21050 Mon Sep 17 00:00:00 2001
From: fiatcode <fiatcode@posteo.com>
Date: Tue, 10 Feb 2026 09:38:58 +0700
Subject: [PATCH 34/34] REFACTOR: split validation into value object

---
 lib/roman_numerals.dart | 23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/lib/roman_numerals.dart b/lib/roman_numerals.dart
index 0490bcb..1309230 100644
--- a/lib/roman_numerals.dart
+++ b/lib/roman_numerals.dart
@@ -1,4 +1,21 @@
+class RomanNumeralInput {
+  static const _minValue = 1;
+  static const _maxValue = 3999;
+
+  final int value;
+
+  RomanNumeralInput(this.value) {
+    if (value < _minValue || value > _maxValue) {
+      throw ArgumentError(
+        'Roman numeral input must be between $_minValue and $_maxValue',
+      );
+    }
+  }
+}
+
 String integerToRoman(int number) {
+  final input = RomanNumeralInput(number);
+
   const conversionRules = [
     (1000, 'M'),
     (900, 'CM'),
@@ -15,12 +32,8 @@ String integerToRoman(int number) {
     (1, 'I'),
   ];
 
-  if (number <= 0 || number > 3999) {
-    throw ArgumentError('Number must be between 1 and 3999');
-  }
-
   final result = StringBuffer();
-  var remaining = number;
+  var remaining = input.value;
 
   for (final (value, symbol) in conversionRules) {
     while (remaining >= value) {