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).

Schism

Answer 1

You can use IsNull.nullValue() method:

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

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

Cantor

it says method nullValue() is not defined – Schism

@user2811419. You need to import IsNull It's a static method in that class. Just do static import, or use IsNull.nullValue(). – Cantor

Add import static org.hamcrest.core.IsNull.nullValue; to your class. – Cantor

In newer versions of Hamcrest the namespace has changed and you need import static org.hamcrest.CoreMatchers.nullValue. – Krys

Answer 2

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

Renatarenate

+1 I generally prefer Hamscrest assertions but this is one case where the Junit assertion is just more readable, IMO. – Saturable

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. – Ornithic

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. – Cissoid

Using an errorCollector is a good reason to use the hamcrest matchers opposed to the assertNull/assertNotNull. – Lyso

Answer 3

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);

Hauteloire

Answer 4

Use the following (from Hamcrest):

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

In Kotlin is is reserved so use:

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

Infringement

Is there an alternative where we don't have to escape the is? – Sherlock

@Sherlock Probably if you use a fully qualified name instead of a static import? – Definitely