重要性：★★★☆☆

可以通过@DisplayName注解给测试类和测试方法自定义名称。

显示名中可以包含空格、特殊字符甚至表情符号等。显示名可以出现在测试报告、测试运行器和IDE中，增强可读性。

下面是代码例子：

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;

@DisplayName("A special test case")
class DisplayNameDemo {

    @Test
    @DisplayName("Custom test name containing spaces")
    void testWithDisplayNameContainingSpaces() {
    }

    @Test
    @DisplayName("╯°□°）╯")
    void testWithDisplayNameContainingSpecialCharacters() {
    }

    @Test
    @DisplayName("😱")
    void testWithDisplayNameContainingEmoji() {
    }
}

在IDEA中执行上面的测试，呈现结果如下：

1. 显示名生成器

JUnit允许创建定制的显示名生成器，通过注解来进行配置。如果和同时存在，前者更优先。

下面是代码例子：

import java.lang.reflect.Method;

import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.DisplayNameGeneration;
import org.junit.jupiter.api.DisplayNameGenerator;
import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.ValueSource;

class DisplayNameGeneratorDemo {

    @Nested
    @DisplayNameGeneration(DisplayNameGenerator.ReplaceUnderscores.class)
    class A_year_is_not_supported {

        @Test
        void if_it_is_zero() {
        }

        @DisplayName("A negative value for year is not supported by the leap year computation.")
        @ParameterizedTest(name = "For example, year {0} is not supported.")
        @ValueSource(ints = { -1, -4 })
        void if_it_is_negative(int year) {
        }

    }

    @Nested
    @DisplayNameGeneration(IndicativeSentences.class)
    class A_year_is_a_leap_year {

        @Test
        void if_it_is_divisible_by_4_but_not_by_100() {
        }

        @ParameterizedTest(name = "Year {0} is a leap year.")
        @ValueSource(ints = { 2016, 2020, 2048 })
        void if_it_is_one_of_the_following_years(int year) {
        }

    }

    static class IndicativeSentences extends DisplayNameGenerator.ReplaceUnderscores {

        @Override
        public String generateDisplayNameForClass(Class testClass) {
            return super.generateDisplayNameForClass(testClass);
        }

        @Override
        public String generateDisplayNameForNestedClass(Class nestedClass) {
            return super.generateDisplayNameForNestedClass(nestedClass) + "...";
        }

        @Override
        public String generateDisplayNameForMethod(Class testClass, Method testMethod) {
            String name = testClass.getSimpleName() + ' ' + testMethod.getName();
            return name.replace('_', ' ') + '.';
        }
    }
}

+-- DisplayNameGeneratorDemo [OK]
  +-- A year is not supported [OK]
  | +-- A negative value for year is not supported by the leap year computation. [OK]
  | | +-- For example, year -1 is not supported. [OK]
  | | '-- For example, year -4 is not supported. [OK]
  | '-- if it is zero() [OK]
  '-- A year is a leap year... [OK]
    +-- A year is a leap year if it is divisible by 4 but not by 100. [OK]
    '-- A year is a leap year if it is one of the following years. [OK]
      +-- Year 2016 is a leap year. [OK]
      +-- Year 2020 is a leap year. [OK]
      '-- Year 2048 is a leap year. [OK]

2. 设置缺省的显示名生成器

可以在JUnit平台配置文件中设置缺省的显示名生成器：

junit.jupiter.displayname.generator.default = \
    org.junit.jupiter.api.DisplayNameGenerator$ReplaceUnderscores

所有的显示名生成器都要实现接口。

测试类和测试方法中的显示名按照下面的优先规则确定：

这一节就讲到这里，下一节我们讲讲"断言"。