fix: rename sum of to summation of

Author: Katalam

README.md

@@ -61,11 +61,11 @@ This plugin affords math related expectations.
     expect(4)->not->toBeFactorialOf(2);
 ```
 
-#### `toBeSumOf()`
+#### `toBeSummationOf()`
 $$\sum\limits_n^k x * 2$$
 ```php
-    expect(2)->toBeSumOf(n: 0, k: 1, static fn (int $x) => $x * 2);
-    expect(3)->not->toBeSumOf(n: 0, k: 1, static fn (int $x) => $x * 2);
+    expect(2)->toBeSumOf(static fn (int $x) => $x * 2, from: 0, to: 1);
+    expect(3)->not->toBeSumOf(static fn (int $x) => $x * 2, from: 0, to: 1);
 ```
 
 #### `toBeProdOf()`

src/Expectation.php

@@ -131,11 +131,25 @@ public function toBeFactorialOf(int $number): PestExpectation
     /**
      * @return PestExpectation<TValue>
      */
-    public function toBeSumOf(int $n, int $k, callable $step): PestExpectation
+    public function toBeSumOf(array $numbers): PestExpectation
     {
         $sum = 0;
+        foreach ($numbers as $number) {
+            expect($number)->toBeNumeric();
+            $sum += $number;
+        }
 
-        foreach (range($n, $k) as $i) {
+        return expect($this->value === $sum)->toBeTrue("$this->value !== $sum");
+    }
+
+    /**
+     * @return PestExpectation<TValue>
+     */
+    public function toBeSummationOf(callable $step, int $from, int $to): PestExpectation
+    {
+        $sum = 0;
+
+        foreach (range($from, $to) as $i) {
             $stepSum = $step($i);
             expect($stepSum)->toBeNumeric();
             $sum += $stepSum;

tests/toBeSummationOf.php

@@ -0,0 +1,31 @@
+<?php
+
+use PHPUnit\Framework\ExpectationFailedException;
+
+it('passes', function (int $sum, int $from, int $to, callable $step): void {
+    expect($sum)->toBeSummationOf($step, $from, $to);
+})->with([
+    [110, 0, 10, static fn (int $i): int => $i * 2],
+    [418, 2, 20, static fn (int $i): int => $i * 2],
+    [1628, 4, 40, static fn (int $i): int => $i * 2],
+    [3630, 6, 60, static fn (int $i): int => $i * 2],
+    [6424, 8, 80, static fn (int $i): int => $i * 2],
+]);
+
+it('passes not', function (callable $step, int $from, int $to): void {
+    expect(1)->not->toBeSummationOf($step, $from, $to);
+})->with([
+    [static fn (int $i): int => $i * 2, 0, 10],
+    [static fn (int $i): int => $i * 2, 2, 20],
+    [static fn (int $i): int => $i * 2, 4, 40],
+    [static fn (int $i): int => $i * 2, 6, 60],
+    [static fn (int $i): int => $i * 2, 8, 80],
+]);
+
+test('failures', function (): void {
+    expect(1)->toBeSummationOf(static fn (int $i): int => $i * 2, 0, 1);
+})->throws(ExpectationFailedException::class);
+
+test('failures not', function (): void {
+    expect(2)->not->toBeSummationOf(static fn (int $i): int => $i * 2, 0 ,1);
+})->throws(ExpectationFailedException::class);