How to mock interface implementation in golang?

myinterface.go

type MyInterface interface {
    fun1() (string)
    fun2() (int)
    fun3() (bool)
}


func Foo(mi MyInterface) (string) {
    return mi.fun1()
}

myinterface_test.go

type MyInterfaceImplementation struct{}

func (mi MyInterfaceImplementation) fun1() (string) {
    return "foobar"
}

func (mi MyInterfaceImplementation) fun2() (int) {
    return int(100)
}

func (mi MyInterfaceImplementation) fun3() (bool) {
    return false
}


func TestFoo(t *testing.T) {
    mi := MyInterfaceImplementation{}
    val := Foo(mi)
    if val != "foobar" {
        t.Errorf("Expected 'foobar', Got %s", mi.fun1())
    }
}

While writing tests for Foo, is it necessary to do a mock implementation of the interface MyInterface (as it requires us to implement fun2 and fun3 as well which are not being used in Foo)?

Is there any way in which we can write tests for Foo wherein we just need to write the mock implementation of fun1 and not for fun2 and fun3?

Also, what's the ideal way to test such use of interfaces in golang?