Experiments with interface embedding

go_Interface_embedding_test.go

package main

import "testing"

type A interface {
	x(key interface{}) interface{}
}

type B struct {
	A
	y *AImpl
}

type AImpl struct{}

func (c *AImpl) x(key interface{}) interface{} {
	return "bar"
}

type C struct {
	A
}

func (c *C) x(key interface{}) interface{} {
	return "foo"
}

func TestEmbeddedInterfaceWorks(t *testing.T) {
	defer assertNoPanic(t)
	c := &C{}
	c.x(1)
}

func TestEmbeddedInterfaceFailsWithEmbeddedAccessWhenNotDefined(t *testing.T) {
	defer assertPanic(t)
	c := &C{}
	c.A.x(1)
}


func TestEmbeddedInterfaceWorksWithEmbeddedAccessIsDefined(t *testing.T) {
	defer assertNoPanic(t)
	c := &C{}
	c.A = &AImpl{}
	c.A.x(1)
}


func TestFieldsDoesNotImplementEmbeddedInterface(t *testing.T) {
	defer assertPanic(t)
	b := &B{y: &AImpl{}}
	b.x(1)
}

func TestFieldsInterfaceWorks(t *testing.T) {
	defer assertNoPanic(t)
	b := &B{y: &AImpl{}}
	b.y.x(1)
}

func assertPanic(t *testing.T) {
	if err := recover(); err != nil {
		return
	}
	t.Fail()
}

func assertNoPanic(t *testing.T) {
	if err := recover(); err != nil {
		t.Fail()
	}
}