Modify the build.gradle file
First of all remeber to modify the module's build.gradle file and not the one in the project.In the android, defaultConfig section add this
testPackage "<package>.test"
testInstrumentationRunner "android.test.InstrumentationTestRunner"
In the dependencies section add this
instrumentTestCompile 'junit:junit:3.8'
Save the file and click the Sync Project with Gradle Files button.
Add unit tests
Under <Project>, <Module>, src add a folder named instrumentTest. Under this create a folder named java and here create a new package named <package>.test.
Now create a class named <ClassName>Test that inherits from android.test.InstrumentationTestCase. In this class individual tests of the class <ClassName> can be written, e.g.
public void testSomeMethodInClass() throws Exception {
final int expected = 1;
final int actual = Class.Method();
assertEquals(expected, actual);
}
Execute test
Right-click on the test method, e.g. testSomeMethodInClass in the example above, choose Run and testSomeMethodInClass. Take the one with the Android icon!
Now a dialog to choose device or emulator will most likely appear. Choose which one to run the test on.
Project structure
<Project>+-.idea
+-gradle
+-<Module>
| +-build
| +-src
| | +-instrumentTest
| | | +-java
| | | +-<package>.test
| | | +-<ClassName>Test
| | +-main
| | +-java
| | | +-<package>
| | | +-<ClassName>
| | +-res
| | | +-drawable...
| | | + ...
| | | +-values...
| | +-AndroidManifest.xml
| +-build.gradle <<------------ THIS ONE!
+-build.gradle <<-------------- *NOT* THIS ONE!
