Added plan of tests

testing/helloworld/go.mod

@@ -0,0 +1,3 @@
+module main.go
+
+go 1.24.5

testing/helloworld/hello_test.go

@@ -0,0 +1,33 @@
+package main
+
+import "testing"
+
+func TestHello(t *testing.T) {
+	t.Run("Say hi to Utii",func(t *testing.T) {
+		got := Hello("Utii","")
+		want := "Hello Utii"
+
+		assertCorrestMsg(t,got,want)
+	})
+
+	t.Run("say 'Hello world' when arg is empty",func(t *testing.T){
+		got := Hello("","")
+		want := "Hello world"
+
+		assertCorrestMsg(t,got,want)
+	})
+
+	t.Run("say 'Hello world' in Russian",func(t *testing.T){
+		got := Hello("Utii","Russian")
+		want := "Привет Utii"
+
+		assertCorrestMsg(t,got,want)
+	})
+}
+
+func assertCorrestMsg(t testing.TB,got, want string) {
+	t.Helper()
+	if got != want {
+		t.Errorf("got %q want %q",got,want)
+	}
+}

testing/helloworld/main.go

@@ -0,0 +1,18 @@
+package main
+
+import "fmt"
+
+const Prefix  = "Hello "
+
+func Hello(name,language string) string {
+	if name == "" {
+		name = "world"
+	}
+	if language == "Russian" {
+		return "Привет " + name
+	}
+	return Prefix + name
+}
+func main() {
+	fmt.Println(Hello("Utii",""))
+}