I am a software tester. I want to practice software testing on mobile/smartphone(preferably on android OS). Are there any open source software projects or applications which i can test on my mobile? I mean to say is there any open source projects for android platform that on which i can practice mobile testing/mobile app testing(mainly manual testing)?
You don't need an Open Source Android app to test. You can use just about any .apk built for Release [Source]. This is unlike iOS apps that have to be built using a Debug build and have the test framework packaged in [Source].
Tools like Xamarin (free with Visual Studio Community for Windows and Xamarin Studio for OSX) or SeeTest (paid app) only ask for the apk file and runs with it.
I use Xamarin but linked SeeTest as my sources since the docs were easier to find.