fn: add benchmark for Map and ForEachConc fns

fn/slice_test.go

@@ -676,3 +676,53 @@ func TestPropCollectOptionsNoNoneUnwrap(t *testing.T) {
 
 	require.NoError(t, quick.Check(f, nil))
 }
+
+// BenchmarkMapVsForEachConc benchmarks the performance of Map and ForEachConc
+// for different workloads and slice sizes. It is used to show that ForEachConc
+// is faster than Map when the workload is expensive.
+func BenchmarkMapVsForEachConc(b *testing.B) {
+	// Test different workload types.
+	workloads := map[string]func(int) int{
+		"Light": func(i int) int {
+			return i + 1
+		},
+		"Expensive": func(i int) int {
+			time.Sleep(time.Millisecond)
+			return i + 1
+		},
+	}
+
+	// Test different slice sizes.
+	for _, size := range []int{10, 100, 1000} {
+		s := make([]int, size)
+		for i := range s {
+			s[i] = i
+		}
+
+		for workload, inc := range workloads {
+			// Benchmark Map.
+			mapConf := fmt.Sprintf("Map-%s-Size-%d", workload, size)
+			b.Run(mapConf, func(b *testing.B) {
+				b.ResetTimer()
+				b.ReportAllocs()
+
+				for i := 0; i < b.N; i++ {
+					Map(s, inc)
+				}
+			})
+
+			// Benchmark ForEachConc.
+			concConf := fmt.Sprintf(
+				"ForEachConc-%s-Size-%d", workload, size,
+			)
+			b.Run(concConf, func(b *testing.B) {
+				b.ResetTimer()
+				b.ReportAllocs()
+
+				for i := 0; i < b.N; i++ {
+					ForEachConc(s, inc)
+				}
+			})
+		}
+	}
+}