What fruit am I?

[lived666]

Have this growing in my garden in Midrand.

Have two trees, one is older and doesn't really fruit and the other one has these, just smaller than a Kiwi, what is fruit is it?

 

[smallearth]

Type of guava maybe? I grew up in a garden that was planted by a horticulturalist who had spent years in China, and this looks like one of those chinese guavas...

 

[Cius]

Do they go yellow eventually?

Edit: Also post a pic of the tree and the leaves if possible.