tests: add another function to the Animal interface

vlib/v/tests/interface_test.v

@@ -8,16 +8,24 @@ struct Cat {
 }
 
 fn (mut c Cat) name() string {
-	assert c.breed == 'Persian'
+	if c.breed != '' {
+		assert c.breed == 'Persian'
+	}
 	return 'Cat'
 }
 
 fn (c &Cat) speak(s string) {
-	assert c.breed == 'Persian'
+	if c.breed != '' {
+		assert c.breed == 'Persian'
+	}
 	assert s == 'Hi !'
 	println('meow')
 }
 
+fn (c Cat) name_detailed(pet_name string) string {
+	return '$pet_name the ${typeof(c)}, breed:${c.breed}'
+}
+
 fn (d Dog) speak(s string) {
 	assert s == 'Hi !'
 	println('woof')
@@ -28,21 +36,24 @@ fn (d Dog) name() string {
 	return 'Dog'
 }
 
-fn test_todo() {
-	if true {}
-	//
-	else{}
+fn (d Dog) name_detailed(pet_name string) string {
+	return '$pet_name the ${typeof(d)}, breed:${d.breed}'
 }
 
-fn perform_speak(s Animal) {
-	s.speak('Hi !')
+fn test_todo() {
+	if true {}
+	else {}
+}
+
+fn perform_speak(a Animal) {
+	a.speak('Hi !')
 	assert true
-	name := s.name()
+	name := a.name()
 	assert name == 'Dog' || name == 'Cat'
-	//if s is Dog {
+	//if a is Dog {
 		//assert name == 'Dog'
 	//}
-	println(s.name())
+	println(a.name())
 }
 
 fn test_perform_speak() {
@@ -59,6 +70,28 @@ fn test_perform_speak() {
 */
 }
 
+fn perform_name_detailed(a Animal) {
+	name_full := a.name_detailed('MyPet')
+	println(name_full)
+	assert name_full.starts_with('MyPet the Dog') || name_full.starts_with('MyPet the Cat')
+}
+
+fn test_perform_name_detailed() {
+	dog := Dog{breed: 'Labrador Retriever'}
+	println('Test on Dog: $dog ...')
+	perform_name_detailed(dog)
+
+	cat := Cat{}
+	println('Test on Cat: $cat ...')
+	perform_speak(cat)
+
+	println('Test on another Cat: ...')
+	perform_speak(Cat{breed: 'Persian'})
+
+	println('Test (dummy/empty) on array of animals ...')
+	handle_animals([dog, cat])
+}
+
 fn handle_animals(a []Animal) {}
 
 interface Register {
@@ -92,6 +125,7 @@ struct Foo {
 
 interface Animal {
 	name() string
+	name_detailed(pet_name string) string
 	speak(s string)
 }