Hamcrest – How to assertThat check null value?
Try to check null value with the Hamcrest assertThat
assertion, but no idea how?
@Test
public void testApp()
{
//ambiguous method call?
assertThat(null, is(null));
}
1. Solution
1.1 To check null value, try is(nullValue)
, remember static import org.hamcrest.CoreMatchers.*
//hello static import, nullValue here
import static org.hamcrest.CoreMatchers.*;
import org.junit.Test;
//...
@Test
public void testApp()
{
//true, check null
assertThat(null, is(nullValue()));
//true, check not null
assertThat("a", is(notNullValue()));
}
1.2 Or this equivalent
import static org.hamcrest.CoreMatchers.*;
import org.hamcrest.core.IsNull;
import org.junit.Test;
//...
@Test
public void testApp()
{
//true, check null
assertThat(null, is(IsNull.nullValue()));
//true, check not null
assertThat("a", is(IsNull.notNullValue()));
}
The CoreMatchers.nullValue()
above (1.1), is a shorthand for IsNull.nullValue
, review the following source code :
org.hamcrest.CoreMatchers.java
public static org.hamcrest.Matcher<java.lang.Object> nullValue() {
return org.hamcrest.core.IsNull.nullValue();
}
P.S Same to notNullValue()
Note
If you prefer JUnit assertion, try
If you prefer JUnit assertion, try
assertNull(null)
and how do i test if i have an arrya with only null elements? resutl like this
[
null
]