JUnit4 TextUtils.isEmpty() gives different result than String.isEmpty()

Question

I know it's weird, but this is what I have.

I'm writing a unit test to check my logic for an Android application. During the test execution, I see that it fails on that line:

if (!TextUtils.isEmpty(fromFile))

Before that if statement fromFile is equals to "" (empty string), but somehow it passes over it and breaks with another logic that doesn't expect empty string.

Diving into debug I saw that fromFile.isEmpty() returns correct result, but TextUtils.isEmpty(fromFile) says that it's not empty.

Open source code, i see:

public static boolean isEmpty(@Nullable CharSequence str) {
   if (str == null || str.length() == 0)
       return true;
   else
       return false;
}

and String.java:

public boolean isEmpty() {
   return value.length == 0;
}

I have following configutation: jdk 1.8.0_77

I would like to avoid whole logic in the app to support String.isEmpty() just to pass the test, since I need to support code before Android API 9, where String.isEmpty is not available, and also TextUtils.isEmpty() do more. Any help with clarification and suggesttions would be helpful.

Has anyone faced it? How should I fix it? Thanks in advance!

Answer 1

For anyone who will face it in future:

I have figured out this by the help of good man, that it is related to android unit test configuration in gradle:

testOptions {
    unitTests.returnDefaultValues = true
}

Which pointed me to a solution: get rid of android dependencies in you buisness logic that you are testing with JUnit(unit test).

I simply replaced android.text.TextUtils with my own method that is in MyStringUtils.java class, that does the same.

Problem was that by deault Android methods did return deafult values while running unit test, and it didn't actually check fromFile value itself, rather then return stub/default value.

Answer 2

TextUtils isn't a JUnit method. If you need to manipulate with TextUtils.isEmpty answer or other method, you can mock it like:

mockStatic(TextUtils.class);
when(TextUtils.isEmpty(any(CharSequence.class))).thenAnswer(new Answer<Boolean>() {
        @Override
        public Boolean answer(InvocationOnMock invocation) throws Throwable {
            CharSequence str = (CharSequence) invocation.getArguments()[0];
            if (str == null || str.length() == 0)
                return true;
            else
                return false;
        }
    });

---

Don't forget to add TextUtils to PrepareForTest list:

@PrepareForTest({TextUtils.class})

Also above mentioned method works for returnDefaultValues configuration:

testOptions {
    unitTests.returnDefaultValues = true
}