Add lab 5 - Stringer (anz-bank#644)

Add lab 5 - Stringer

05_stringer/alextmz/main.go

@@ -0,0 +1,19 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+type ipAddr [4]byte
+
+var out io.Writer = os.Stdout
+
+func main() {
+	fmt.Fprintln(out, ipAddr{127, 0, 0, 1})
+}
+
+func (i ipAddr) String() string {
+	return fmt.Sprintf("%d.%d.%d.%d", i[0], i[1], i[2], i[3])
+}

05_stringer/alextmz/main_test.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIPAddrString(t *testing.T) {
+	var tests = map[string]struct {
+		arg  ipAddr
+		want string
+	}{
+		"empty IPv4": {
+			ipAddr{},
+			"0.0.0.0",
+		},
+		"8bits IPv4": {
+			ipAddr{254},
+			"254.0.0.0",
+		},
+		"16bits IPv4": {
+			ipAddr{254, 254},
+			"254.254.0.0",
+		},
+		"24bits IPv4": {
+			ipAddr{254, 254, 254},
+			"254.254.254.0",
+		},
+		"full IPv4": {
+			ipAddr{254, 254, 254, 254},
+			"254.254.254.254",
+		},
+	}
+
+	for name, test := range tests {
+		test := test
+		t.Run(name, func(t *testing.T) {
+			actual := test.arg.String()
+			assert.Equal(t, test.want, actual)
+		})
+	}
+}
+
+func TestMain(t *testing.T) {
+	want := "127.0.0.1\n"
+	var buf bytes.Buffer
+	out = &buf
+	main()
+	got := buf.String()
+	assert.Equal(t, want, got)
+}