countdown: add basic countdown

countdown/countdown.go

@@ -0,0 +1,21 @@
+package countdown
+
+import (
+	"fmt"
+	"io"
+	"time"
+)
+
+const (
+	finalWord      = "Go!"
+	countdownStart = 3
+)
+
+func Countdown(out io.Writer) {
+	for i := countdownStart; i > 0; i-- {
+		fmt.Fprintf(out, "%d\n", i)
+		// This is difficult to test!
+		time.Sleep(1 * time.Second)
+	}
+	fmt.Fprint(out, finalWord)
+}

countdown/countdown_test.go

@@ -0,0 +1,22 @@
+package countdown
+
+import (
+	"bytes"
+	"testing"
+)
+
+func TestCountdown(t *testing.T) {
+	buffer := &bytes.Buffer{}
+
+	Countdown(buffer)
+
+	got := buffer.String()
+	want := `3
+2
+1
+Go!`
+
+	if got != want {
+		t.Errorf("got %q want %q", got, want)
+	}
+}

main.go

@@ -0,0 +1,12 @@
+package main
+
+import (
+	"gobytest/countdown"
+	"os"
+)
+
+func main() {
+	// greet.Greet(os.Stdout, "Elodie")
+
+	countdown.Countdown(os.Stdout)
+}