From 3932b66634a3fa3df35a90862a2a6b9da9253aef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Krejczinger=20=C3=81rp=C3=A1d?=
 <krejczinger.arpad@gmail.com>
Date: Mon, 16 Mar 2026 00:22:46 +0100
Subject: [PATCH] Add array sum module

---
 arrays/sum.go      | 10 ++++++++++
 arrays/sum_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 arrays/sum.go
 create mode 100644 arrays/sum_test.go

diff --git a/arrays/sum.go b/arrays/sum.go
new file mode 100644
index 0000000..e5bb950
--- /dev/null
+++ b/arrays/sum.go
@@ -0,0 +1,10 @@
+package main
+
+func Sum(numbers []int) int {
+	sum := 0
+	// example: for ... in equivalent, first var has index
+	for _, number := range numbers {
+		sum += number
+	}
+	return sum
+}
diff --git a/arrays/sum_test.go b/arrays/sum_test.go
new file mode 100644
index 0000000..4393a4c
--- /dev/null
+++ b/arrays/sum_test.go
@@ -0,0 +1,27 @@
+package main
+
+import "testing"
+
+func TestSum(t *testing.T) {
+	t.Run("collection of 5 numbers", func(t *testing.T) {
+		numbers := []int{1, 2, 3, 4, 5}
+
+		got := Sum(numbers)
+		want := 15
+
+		if got != want {
+			t.Errorf("got %d want %d given, %v", got, want, numbers)
+		}
+	})
+
+	t.Run("collection of any size", func(t *testing.T) {
+		numbers := []int{1, 2, 3}
+
+		got := Sum(numbers)
+		want := 6
+
+		if got != want {
+			t.Errorf("got %d want %d given, %v", got, want, numbers)
+		}
+	})
+}