应使用 AssertNull 或 AssertNotNull

Question

This is a pretty dumb question but my first time with unit testing so: lets say I have an object variable like obj and I want my unit test to Fail if this obj is Null. so for assertions, should I say AssertNull or AssertNotNull? I get confused how they are named.

Answer 1

Use assertNotNull(obj) . assert means must be .

Answer 2

The AssertNotNull() method means "a passed parameter must not be null ": if it is null then the test case fails.
The AssertNull() method means "a passed parameter must be null ": if it is not null then the test case fails.

String str1 = null;
String str2 = "hello";              

// Success.
AssertNotNull(str2);

// Fail.
AssertNotNull(str1);

// Success.
AssertNull(str1);

// Fail.
AssertNull(str2);

Answer 3

assertNotNull asserts that the object is not null. If it is null the test fails, so you want that.

Answer 4

我只是想补充一点，如果你想要写一个特殊的文本，如果它是null，那么就像你那样

  Assert.assertNotNull("The object you enter return null", str1)

Answer 5

In JUnit 4, IDEA (UE 2020) suggests using assertThat(..., notNullValue()); instead of Assert.assertNotNull(...) .

For instance:

1. IDEA warning
2. IDEA suggestions
3. IDEA fix