Android Studio unit testing: read data (input) file

Question

In a unit test, how can I read data from a json file on my (desktop) file system, without hardcoding the path?

I would like to read test input (for my parsing methods) from a file instead of creating static Strings.

The file is in the same location as my unit testing code, but I can also place it somewhere else in the project if needed. I am using Android Studio.

Answer 1

Depending on android-gradle-plugin version:

1. version 1.5 and higher:

Just put json file to src/test/resources/test.json and reference it as

classLoader.getResource("test.json"). 

No gradle modification is needed.

2. version below 1.5: (or if for some reason above solution doesn't work)

1. Ensure you're using at least Android Gradle Plugin version 1.1. Follow the link to set up Android Studio correctly.

2. Create test directory. Put unit test classes in java directory and put your resources file in res directory. Android Studio should mark them like follow:

   

3. Create gradle task to copy resources into classes directory to make them visible for classloader:

   android{
      ...
   }
   
   task copyResDirectoryToClasses(type: Copy){
       from "${projectDir}/src/test/res"
       into "${buildDir}/intermediates/classes/test/debug/res"
   }
   
   assembleDebug.dependsOn(copyResDirectoryToClasses)
   

4. Now you can use this method to get File reference for the file resource:

   private static File getFileFromPath(Object obj, String fileName) {
       ClassLoader classLoader = obj.getClass().getClassLoader();
       URL resource = classLoader.getResource(fileName);
       return new File(resource.getPath());
   }
   
   @Test
   public void fileObjectShouldNotBeNull() throws Exception {
       File file = getFileFromPath(this, "res/test.json");
       assertThat(file, notNullValue());
   }
   

5. Run unit test by Ctrl+Shift+F10 on whole class or specyfic test method.