Hamcrest –如何断言检查空值？

尝试使用Hamcrest assertThat断言检查空值，但不知道如何做？

@Test
	public void testApp()
    {
        //ambiguous method call?
        assertThat(null, is(null));
    }

1.解决方案

1.1要检查空值，请尝试is(nullValue) ，请记住静态导入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或等效

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()));
    }

上面（1.1）的CoreMatchers.nullValue()是IsNull.nullValue的简写，请查看以下源代码：

org.hamcrest.CoreMatchers.java

public static org.hamcrest.Matcher<java.lang.Object> nullValue() {
    return org.hamcrest.core.IsNull.nullValue();
  }

PS与notNullValue()相同

注意
如果您喜欢JUnit声明，请尝试assertNull(null)

参考文献

1. Hamcrest – IsNull JavaDoc
2. Hamcrest官方网站

标签： 断言 hamcrest

From: https://mkyong.com/unittest/hamcrest-how-to-assertthat-check-null-value/