How to assertThat something is null with Hamcrest?

Question

How would I assertThat something is null?

for example

 assertThat(attr.getValue(), is(""));

But I get an error saying that I cannot have null in is(null).

score 291 · Accepted Answer · edited Dec 02 '14 at 03:38

291

import static org.hamcrest.Matchers.is;
import static org.hamcrest.Matchers.nullValue;

assertThat(attr.getValue(), is(nullValue()));

edited Dec 02 '14 at 03:38

Jared Burrows

answered Sep 24 '13 at 17:00

Rohit Jain

it says method nullValue() is not defined – user2811419 Sep 24 '13 at 17:02
2

@user2811419. You need to import `IsNull` It's a static method in that class. Just do `static import`, or use `IsNull.nullValue()`. – Rohit Jain Sep 24 '13 at 17:03
Add `import static org.hamcrest.core.IsNull.nullValue;` to your class. – Rohit Jain Sep 24 '13 at 17:05
5

In newer versions of Hamcrest the namespace has changed and you need `import static org.hamcrest.CoreMatchers.nullValue`. – ThomasW Jan 08 '16 at 07:18

score 35 · Answer 2 · edited Jul 31 '16 at 10:47

35

why not use assertNull(object) / assertNotNull(object) ?

edited Jul 31 '16 at 10:47

blackpanther

answered Sep 24 '13 at 17:00

Chetya

9

+1 I generally prefer Hamscrest assertions but this is one case where the Junit assertion is just more readable, IMO. – spaaarky21 Oct 31 '14 at 18:16
9

assertThat() give much better logging that many of the other assert* methods. The test-coding standard that I use favors assertThat() over all other assertion methods for this reason. – efelton Apr 23 '15 at 15:58
3

The main advantage when using assertThat vs assertNul is that it is closer to an Englsih spoken phrase, just try to read any of your assertions to check it up. – belgoros Jul 06 '16 at 09:28
Using an errorCollector is a good reason to use the hamcrest matchers opposed to the assertNull/assertNotNull. – Tyler MacMillan Jan 04 '17 at 17:03

score 17 · Answer 3 · answered Sep 24 '13 at 17:04

17

If you want to hamcrest, you can do

import static org.hamcrest.Matchers.nullValue;

assertThat(attr.getValue(), is(nullValue()));

In Junit you can do

import static junit.framework.Assert.assertNull;
assertNull(object);

answered Sep 24 '13 at 17:04

Sajan Chandran

score 11 · Answer 4 · edited May 10 '20 at 14:20

11

Use the following (from Hamcrest):

assertThat(attr.getValue(), is(nullValue()));

In Kotlin is is reserved so use:

assertThat(attr.getValue(), `is`(nullValue()));

edited May 10 '20 at 14:20

Idrizi.A

answered Sep 24 '13 at 17:02

blackpanther

1

Is there an alternative where we don't have to escape the `is`? – VIN Jul 17 '20 at 02:13
@VIN Probably if you use a fully qualified name instead of a static import? – Tazaf May 01 '23 at 14:40

4 Answers4