assert that a list is not empty in JUnit

Question

I want to assert that a list is not empty in JUnit 4, when I googled about it I found this post : Checking that a List is not empty in Hamcrest which was using Hamcrest.

assertThat(result.isEmpty(), is(false));

which gives me this error :

The method is(boolean) is undefined for the type MaintenanceDaoImplTest

how can I do that without using Hamcrest.

See also here http://stackoverflow.com/questions/3631110/checking-that-a-list-is-not-empty-in-hamcrest — Florian Schaetz, Feb 17 '16 at 10:41
Just for reference: `assertThat(items, IsCollectionWithSize.hasSize(greaterThan(1)))` checks the size of the collection. But unfortunately it doesn't print items in the collection in case of failure :( — Ilya Serbis, Sep 17 '20 at 20:52

score 125 · Accepted Answer · answered Feb 17 '16 at 10:23

125

You can simply use

assertFalse(result.isEmpty());

Regarding your problem, it's simply caused by the fact that you forgot to statically import the is() method from Hamcrest;

import static org.hamcrest.CoreMatchers.is;

answered Feb 17 '16 at 10:23

JB Nizet

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now the better approach is the `assertThat(myList, is(not(empty())));` – Giulio Caccin Jul 24 '19 at 15:12
@GiulioCaccin Mentioning the import classes would be helpful. – t_sologub Apr 14 '20 at 03:57
I did not mention it because the proper answer from LazerBanana is right here on page. https://stackoverflow.com/a/51279675/1636173 – Giulio Caccin Apr 14 '20 at 04:02
How would you extend this to check if a file is empty? – KLDavenport Jul 25 '21 at 18:08

LazerBanana · Answer 2 · 2018-08-24T08:51:44.593

41

This reads quite nicely and uses Hamcrest. Exactly what you asked for ;) Always nice when the code reads like a comment.

assertThat(myList, is(empty()));
assertThat(myList, is(not(empty())));

You can add is as a static import to your IDE as I know that eclipse and IntelliJ is struggling with suggesting it even when it is on the classpath.

IntelliJ

Settings -> Code Style -> Java -> Imports

Eclipse

Prefs -> Java -> Editor -> Content Assist -> Favourites

And the import itself is import static org.hamcrest.CoreMatchers.is;

edited Aug 24 '18 at 08:51

answered Jul 11 '18 at 07:33

LazerBanana

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what about `empty()` it's not resolved for me, is it user-defined too or need static import? – Basheer AL-MOMANI May 18 '20 at 15:44
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@basheer : import static org.hamcrest.Matchers.empty; – sotix Dec 08 '20 at 13:13

score 5 · Answer 3 · edited Jan 15 '21 at 14:45

5

You can check if your list is not equal an Empty List (Collections.EMPTY_LIST), try this:

Assertions.assertNotEquals(Collections.EMPTY_LIST, yourList);

edited Jan 15 '21 at 14:45

phoenixstudio

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answered Jan 15 '21 at 12:24

Ricardo Nascimento

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score 1 · Answer 4 · answered Oct 20 '20 at 10:26

1

I like to use

Assert.assertEquals(List.of(), result)

That way, you get a really good error message if the list isn't empty. E.g.

java.lang.AssertionError: 
Expected :[]
Actual   :[something unexpected]

answered Oct 20 '20 at 10:26

Harry

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score 1 · Answer 5 · answered Nov 26 '20 at 13:19

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assertEquals(Collections.Empty_List,Collections.emptyList())

Try this.

answered Nov 26 '20 at 13:19

Arindam

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score -2 · Answer 6 · edited Aug 16 '18 at 10:45

-2

I was also looking for something similar, but the easiest work around can be

Assert.AreEqual(result.Count, 0);

When the collection has no records.

edited Aug 16 '18 at 10:45

Brian Tompsett - 汤莱恩

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answered Aug 16 '18 at 10:27

Sahil

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score -2 · Answer 7 · answered Apr 07 '20 at 08:30

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You can change "is" to "equalTo": assertThat(result.isEmpty(), equalTo(false));

answered Apr 07 '20 at 08:30

Ruslan Omelchenko

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What imports are you using for this? Is it without using Hamcrest? – Scratte Apr 07 '20 at 09:16

assert that a list is not empty in JUnit

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