From 8f6bad7a6f7cfc73ba1cbc5bba7984cff4292903 Mon Sep 17 00:00:00 2001
From: RuiAlonso <rui.alonso@verygood.ventures>
Date: Mon, 7 Mar 2022 14:12:33 +0100
Subject: [PATCH] test: tests for maths methods

---
 packages/maths/lib/src/maths.dart       | 18 +++--
 packages/maths/pubspec.yaml             | 10 ++-
 packages/maths/test/src/maths_test.dart | 87 +++++++++++++++++++++++--
 3 files changed, 101 insertions(+), 14 deletions(-)

diff --git a/packages/maths/lib/src/maths.dart b/packages/maths/lib/src/maths.dart
index ea447db5..bdb31d43 100644
--- a/packages/maths/lib/src/maths.dart
+++ b/packages/maths/lib/src/maths.dart
@@ -3,6 +3,7 @@ import 'package:flame/extensions.dart';
 
 /// Method to calculate all points (with a required precision amount of them)
 /// of a circumference based on angle, offsetAngle and radius
+/// https://en.wikipedia.org/wiki/Trigonometric_functions
 List<Vector2> calculateArc({
   required Vector2 center,
   required double radius,
@@ -47,9 +48,9 @@ List<Vector2> calculateBezierCurve({
       final point = controlPoints[i];
 
       xCoord +=
-          _binomial(n, i) * math.pow(1 - t, n - i) * math.pow(t, i) * point.x;
+          binomial(n, i) * math.pow(1 - t, n - i) * math.pow(t, i) * point.x;
       yCoord +=
-          _binomial(n, i) * math.pow(1 - t, n - i) * math.pow(t, i) * point.y;
+          binomial(n, i) * math.pow(1 - t, n - i) * math.pow(t, i) * point.y;
     }
     points.add(Vector2(xCoord, yCoord));
 
@@ -61,21 +62,24 @@ List<Vector2> calculateBezierCurve({
 
 /// Method to calculate the binomial coefficient of 'n' and 'k'
 /// https://en.wikipedia.org/wiki/Binomial_coefficient
-num _binomial(num n, num k) {
+num binomial(num n, num k) {
   assert(0 <= k && k <= n, 'Range 0<=k<=n');
   if (k == 0 || n == k) {
     return 1;
   } else {
-    return _factorial(n) / (_factorial(k) * _factorial(n - k));
+    return factorial(n) / (factorial(k) * factorial(n - k));
   }
 }
 
 /// Method to calculate the factorial of some number 'n'
 /// https://en.wikipedia.org/wiki/Factorial
-num _factorial(num n) {
-  if (n == 1) {
+num factorial(num n) {
+  assert(0 <= n, 'Non negative n');
+  if (n == 0) {
+    return 1;
+  } else if (n == 1) {
     return 1;
   } else {
-    return n * _factorial(n - 1);
+    return n * factorial(n - 1);
   }
 }
diff --git a/packages/maths/pubspec.yaml b/packages/maths/pubspec.yaml
index 3b4b863c..b037f4a4 100644
--- a/packages/maths/pubspec.yaml
+++ b/packages/maths/pubspec.yaml
@@ -6,10 +6,14 @@ publish_to: none
 environment:
   sdk: ">=2.16.0 <3.0.0"
 
+dependencies: 
+  flame: ^1.0.0
+  flutter:
+    sdk: flutter
+
 dev_dependencies:
-  coverage: ^1.1.0
+  flutter_test:
+    sdk: flutter
   mocktail: ^0.2.0
   test: ^1.19.2
   very_good_analysis: ^2.4.0
-dependencies: 
-  flame: ^1.0.0
diff --git a/packages/maths/test/src/maths_test.dart b/packages/maths/test/src/maths_test.dart
index dceedab8..8faa57cf 100644
--- a/packages/maths/test/src/maths_test.dart
+++ b/packages/maths/test/src/maths_test.dart
@@ -1,11 +1,90 @@
-// ignore_for_file: prefer_const_constructors
+// ignore_for_file: prefer_const_constructors, cascade_invocations
+import 'package:flutter_test/flutter_test.dart';
 import 'package:maths/maths.dart';
-import 'package:test/test.dart';
+
+class Binomial {
+  Binomial({required this.n, required this.k});
+
+  final num n;
+  final num k;
+}
 
 void main() {
   group('Maths', () {
-    test('can be instantiated', () {
-      expect(Maths(), isNotNull);
+    group('calculateArc', () {});
+    group('calculateBezierCurve', () {});
+
+    group('binomial', () {
+      test('fails if k is negative', () {
+        expect(() => binomial(1, -1), throwsAssertionError);
+      });
+      test('fails if n is negative', () {
+        expect(() => binomial(-1, 1), throwsAssertionError);
+      });
+      test('fails if n < k', () {
+        expect(() => binomial(1, 2), throwsAssertionError);
+      });
+      test('for a specific input gives a correct value', () {
+        final binomialInputsToExpected = {
+          Binomial(n: 0, k: 0): 1,
+          Binomial(n: 1, k: 0): 1,
+          Binomial(n: 1, k: 1): 1,
+          Binomial(n: 2, k: 0): 1,
+          Binomial(n: 2, k: 1): 2,
+          Binomial(n: 2, k: 2): 1,
+          Binomial(n: 3, k: 0): 1,
+          Binomial(n: 3, k: 1): 3,
+          Binomial(n: 3, k: 2): 3,
+          Binomial(n: 3, k: 3): 1,
+          Binomial(n: 4, k: 0): 1,
+          Binomial(n: 4, k: 1): 4,
+          Binomial(n: 4, k: 2): 6,
+          Binomial(n: 4, k: 3): 4,
+          Binomial(n: 4, k: 4): 1,
+          Binomial(n: 5, k: 0): 1,
+          Binomial(n: 5, k: 1): 5,
+          Binomial(n: 5, k: 2): 10,
+          Binomial(n: 5, k: 3): 10,
+          Binomial(n: 5, k: 4): 5,
+          Binomial(n: 5, k: 5): 1,
+          Binomial(n: 6, k: 0): 1,
+          Binomial(n: 6, k: 1): 6,
+          Binomial(n: 6, k: 2): 15,
+          Binomial(n: 6, k: 3): 20,
+          Binomial(n: 6, k: 4): 15,
+          Binomial(n: 6, k: 5): 6,
+          Binomial(n: 6, k: 6): 1,
+        };
+        binomialInputsToExpected.forEach((input, value) {
+          expect(binomial(input.n, input.k), value);
+        });
+      });
+    });
+    group('factorial', () {
+      test('fails if negative number', () {
+        expect(() => factorial(-1), throwsAssertionError);
+      });
+      test('for a specific input gives a correct value', () {
+        final factorialInputsToExpected = {
+          0: 1,
+          1: 1,
+          2: 2,
+          3: 6,
+          4: 24,
+          5: 120,
+          6: 720,
+          7: 5040,
+          8: 40320,
+          9: 362880,
+          10: 3628800,
+          11: 39916800,
+          12: 479001600,
+          13: 6227020800,
+        };
+        factorialInputsToExpected.forEach((input, expected) {
+          expect(factorial(input), expected);
+        });
+      });
     });
   });
 }