How to set current tab in viewpager with tablayout

Question

I have a custom viewpager (with swiping disabled for reasons) working with a tablayout. The content changes based on which tab is selected. I want to test this using espresso: 1) Click on a particular tab 2) Check some data in a particular page of the tab How can I do that. I am a novice to espresso

Augend

Answer 1

There are several ways of doing this, an easy one is to select the element by the tab title, I use this code:

Matcher<View> matcher = allOf(withText("TAB TITLE"),
            isDescendantOfA(withId(R.id.customTab)));
onView(matcher).perform(click());
SystemClock.sleep(800); // Wait a little until the content is loaded

You only have to adapt the matcher to your layout. Then, check the content.

For example:

onView(withId(R.id.someId)).check(matches(isCompletelyDisplayed()));

or:

onView(withText(R.string.someText)).check(matches(isCompletelyDisplayed()));

You can find examples here in the Specifying a View Matcher section: http://developer.android.com/intl/es/training/testing/ui-testing/espresso-testing.html

If you are using a RecyclerView to show the content of the tabs have a look at this: Espresso RecyclerView inside ViewPager

Contend

What if the tab has only an icon and no text, how to capture it? withIcon() does not exist in Espresso. Any other alternative? – Littlest

In that case you can still use the withId, withTagValue or create a custom matcher instead of the withText one – Contend

From my actual code I passed in a setTag() within my tabLayout.getTabAt(i).setTag(...) but withTagValue() takes a Matcher<Object> as parameter and not a string. Regarding withId(), tabLayout.getTabAt(i) does not have any method for setId(). I can only set the id of the whole layout and not the individual single tab. – Littlest

You can use withTagValue this way: onView(withTagValue(is((Object) tagValueString))) using the Matcher.is method to find views with that tag – Contend

I implemented your suggestions but my test is failing. I opened the following question #51029455 – Littlest

Answer 2

Espresso should be used when you clearly know what is expected in the UI and so you can verify the same.

In your case, to go to any tab, you can use view action to tap on that tab. To verify the data, first you should know what data is expected to be there on that tab and then just use matchers to check if they are displayed or not.

Silvasilvain

This doesn't explain how to select a specific tab in a ViewPager. – Agonist