boolean addResult = source.add("foo")
        provider1.value = []

        then:
        addResult
        source.iterator().collect() == ["foo"]
    }

    def "adding is not ignored when an unrealized provider currently has the same value"() {
        def provider1 = setProvider("foo")

        when:
        source.addPendingCollection(provider1)
        boolean addResult = source.add("foo")