add aggr functions tests

funcs_aggregation_test.go

@@ -0,0 +1,32 @@
+package handy
+
+import (
+    "slices"
+    "testing"
+)
+
+func TestReduce(t *testing.T) {
+    list := NewList(1, 2, 3, 4, 5)
+    actual := Reduce(list, 0, func(acc, each int) int {
+        return acc + each
+    })
+    expect := 15
+    if actual != expect {
+        t.Fatalf("test Reduce, expect: %v, actual: %v", expect, actual)
+    }
+}
+
+func TestScan(t *testing.T) {
+    list := NewList(1, 2, 3, 4, 5)
+    e := Scan(list, 0, func(acc, each int) int {
+        return acc + each
+    })
+    actual := []int{}
+    for v := range e.Iter() {
+        actual = append(actual, v)
+    }
+    expect := []int{1, 3, 6, 10, 15}
+    if !slices.Equal(actual, expect) {
+        t.Fatalf("test Scan, expect: %v, actual: %v", expect, actual)
+    }
+}