From 05736cec30b935bf52e4f1d6656776f2c03f094e Mon Sep 17 00:00:00 2001
From: "Christopher C. Wells" <git@chris-wells.net>
Date: Thu, 8 Apr 2021 16:54:01 -0700
Subject: [PATCH] Add tests and documentation for nutrient rounding changes

---
 app/Support/Nutrients.php            | 43 ++++++++++++++++++++++---
 tests/Unit/Support/NutrientsTest.php | 48 ++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 5 deletions(-)
 create mode 100644 tests/Unit/Support/NutrientsTest.php

diff --git a/app/Support/Nutrients.php b/app/Support/Nutrients.php
index a582465..354e5a6 100644
--- a/app/Support/Nutrients.php
+++ b/app/Support/Nutrients.php
@@ -198,14 +198,47 @@ class Nutrients
      * zero.
      *
      * @url https://labelcalc.com/food-labeling/a-guide-to-using-fda-rounding-rules-for-your-food-label/
+     *
+     * @throws \InvalidArgumentException
      */
     public static function round(float $amount, string $nutrient): float {
         return match ($nutrient) {
-            'calories' => ($amount < 5 ? 0 : ($amount <= 50 ? round( $amount / 5 ) * 5 : round( $amount / 10 ) * 10)),
-            'carbohydrates', 'protein' => ($amount < 1 ? 0 : round( $amount)),
-            'cholesterol', 'fat'  => ($amount < 0.5 ? 0 : ($amount <= 5 ? round( $amount / 5, 1 ) * 5 : round($amount))),
-            'sodium' => ($amount < 5 ? 0 : ($amount <= 140 ? round( $amount / 5 ) * 5 : round( $amount / 10 ) * 10)),
-            default => throw new \UnexpectedValueException()
+
+            /*
+             * Calories:
+             *  - Less than 5 goes to zero.
+             *  - Between 5 and 50 rounds to nearest number divisible by 5.
+             *  - Greater than 50 rounds to nearest number divisible by 10.
+             */
+            'calories' => ($amount < 5 ? 0 : ($amount <= 50 ? round($amount / 5 ) * 5 : round($amount / 10 ) * 10)),
+
+            /*
+             * Carbohydrates and protein:
+             *  - Less than 1 goes to zero.
+             *  - Greater than 1 rounds to nearest whole.
+             */
+            'carbohydrates', 'protein' => ($amount < 1 ? 0 : round($amount)),
+
+            /*
+             * Cholesterol and fat:
+             *  - Less than 0.5 goes to zero.
+             *  - Between 0.5 and 5 rounds to nearest half.
+             *  - Greater than 5 rounds to nearest whole.
+             */
+            'cholesterol', 'fat'  => ($amount < 0.5 ? 0 : ($amount <= 5 ? round($amount / 5, 1 ) * 5 : round($amount))),
+
+            /*
+             * Sodium:
+             *  - Less than 5 goes to zero.
+             *  - Between 5 and 140 rounds to nearest number divisible by 5.
+             *  - Greater than 140 rounds to nearest number divisible by 10.
+             */
+            'sodium' => ($amount < 5 ? 0 : ($amount <= 140 ? round($amount / 5 ) * 5 : round($amount / 10 ) * 10)),
+
+            /*
+             * Anything else excepts!
+             */
+            default => throw new \InvalidArgumentException("Unrecognized nutrient {$nutrient}.")
         };
     }
 }
diff --git a/tests/Unit/Support/NutrientsTest.php b/tests/Unit/Support/NutrientsTest.php
new file mode 100644
index 0000000..e7af25c
--- /dev/null
+++ b/tests/Unit/Support/NutrientsTest.php
@@ -0,0 +1,48 @@
+<?php
+
+namespace Tests\Unit\Support;
+
+use App\Support\Nutrients;
+use PHPUnit\Framework\TestCase;
+
+class NutrientsTest extends TestCase
+{
+
+    /**
+     * Test nutrient rounding.
+     *
+     * @dataProvider nutrientAmountsProvider
+     *
+     * @see \App\Support\Nutrients::round()
+     */
+    public function testNutrientRounding(float $amount, string $nutrient, float $expectedFloat): void
+    {
+        $result = Nutrients::round($amount, $nutrient);
+        $this->assertIsFloat($result);
+        $this->assertEquals($expectedFloat, $result);
+    }
+
+    public function testNutrientRoundingExcepts(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        Nutrients::round(1, 'pancake');
+    }
+
+    /**
+     * Data providers.
+     */
+
+    /**
+     * Provide nutrient amounts for and expected rounded results.
+     */
+    public function nutrientAmountsProvider(): array {
+        return [
+            [0, 'calories', 0], [1, 'calories', 0], [2, 'calories', 0], [3, 'calories', 0], [4, 'calories', 0], [5, 'calories', 5], [21, 'calories', 20], [23, 'calories', 25], [45, 'calories', 45], [50, 'calories', 50],
+            [0, 'carbohydrates', 0], [0.1, 'carbohydrates', 0], [0.2, 'carbohydrates', 0], [0.3, 'carbohydrates', 0], [0.4, 'carbohydrates', 0], [0.5, 'carbohydrates', 0], [0.9, 'carbohydrates', 0], [1, 'carbohydrates', 1], [2.25, 'carbohydrates', 2], [2.75, 'carbohydrates', 3],
+            [0, 'protein', 0], [0.1, 'protein', 0], [0.2, 'protein', 0], [0.3, 'protein', 0], [0.4, 'protein', 0], [0.5, 'protein', 0], [0.9, 'protein', 0], [1, 'protein', 1], [2.25, 'protein', 2], [2.75, 'protein', 3],
+            [0, 'cholesterol', 0], [0.1, 'cholesterol', 0], [0.2, 'cholesterol', 0], [0.3, 'cholesterol', 0], [0.4, 'cholesterol', 0], [0.5, 'cholesterol', 0.5], [0.9, 'cholesterol', 1], [1, 'cholesterol', 1], [1.2, 'cholesterol', 1], [1.4, 'cholesterol', 1.5], [5, 'cholesterol', 5], [6, 'cholesterol', 6], [6.25, 'cholesterol', 6], [6.75, 'cholesterol', 7],
+            [0, 'fat', 0], [0.1, 'fat', 0], [0.2, 'fat', 0], [0.3, 'fat', 0], [0.4, 'fat', 0], [0.5, 'fat', 0.5], [0.9, 'fat', 1], [1, 'fat', 1], [1.2, 'fat', 1], [1.4, 'fat', 1.5], [5, 'fat', 5], [6, 'fat', 6], [6.25, 'fat', 6], [6.75, 'fat', 7],
+            [0, 'sodium', 0], [1, 'sodium', 0], [2, 'sodium', 0], [3, 'sodium', 0], [4, 'sodium', 0], [5, 'sodium', 5], [6, 'sodium', 5], [7, 'sodium', 5], [8, 'sodium', 10], [9, 'sodium', 10], [10, 'sodium', 10], [139, 'sodium', 140], [140, 'sodium', 140], [146, 'sodium', 150], [151, 'sodium', 150], [159, 'sodium', 160],
+        ];
+    }
+}