Android test code coverage report for files in other module

My Application has two Projects，Project A provide a Fragment for Project B. Thus I put Instrument Tests in Project B.
The problem is:
I can generate the Code Coverage Reports for those Instrument Tests, but those reports only contain codes in project B.
How can I include codes in project A into those Test Coverage Reports?

Below is the dependencies of project B:
dependencies { compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2',
{
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:24.2.1'
testCompile 'junit:junit:4.12'
compile project(":ProjectA")
}