在 Java 中测试构建器模式

Question

我们在代码库中广泛使用构建器模式，构建的对象都有一个toBuilder()方法。我想编写一个单元测试来确保方法中没有忘记任何字段toBuilder()，即对于任何可构建的对象，我想大致像这样进行测试

MyClass obj = getTestObjectWithRandomData();
assertEquals(obj, obj.toBuilder().build());

现在，我可以很容易地编写一个基本版本，getTestObjectWithRandomData()它使用反射为任何对象的字段分配一堆值。然而，障碍是build()通常包含大量的验证检查，例如，如果某个整数不在合理范围内，则会抛出异常。编写一个getTestObjectWithRandomData()符合所有这些特定于类的验证检查的通用版本是不可能的。

那么，我怎样才能做我想做的事呢？我很想将构造和验证代码分离到不同的方法中，这样测试就不会在验证时出错，但这意味着人们必须记住validate()在创建对象后调用或执行任何操作。不好。

还有其他想法吗？

Answer 1

使用龙目岛怎么样？那会是你的一个选择吗？它会自动生成构建器代码，您再也不用担心它了。 https://projectlombok.org/features/Builder

简单地注释你的类 @Builder

与龙目岛

import lombok.Builder;
import lombok.Singular;
import java.util.Set;

@Builder
public class BuilderExample {
  private String name;
  private int age;
  @Singular private Set<String> occupations;
}

香草爪哇

import java.util.Set;

public class BuilderExample {
  private String name;
  private int age;
  private Set<String> occupations;

  BuilderExample(String name, int age, Set<String> occupations) {
    this.name = name;
    this.age = age;
    this.occupations = occupations;
  }

  public static BuilderExampleBuilder builder() {
    return new BuilderExampleBuilder();
  }

  public static class BuilderExampleBuilder {
    private String name;
    private int age;
    private java.util.ArrayList<String> occupations;

    BuilderExampleBuilder() {
    }

    public BuilderExampleBuilder name(String name) {
      this.name = name;
      return this;
    }

    public BuilderExampleBuilder age(int age) {
      this.age = age;
      return this;
    }

    public BuilderExampleBuilder occupation(String occupation) {
      if (this.occupations == null) {
        this.occupations = new java.util.ArrayList<String>();
      }

      this.occupations.add(occupation);
      return this;
    }

    public BuilderExampleBuilder occupations(Collection<? extends String> occupations) {
      if (this.occupations == null) {
        this.occupations = new java.util.ArrayList<String>();
      }

      this.occupations.addAll(occupations);
      return this;
    }

    public BuilderExampleBuilder clearOccupations() {
      if (this.occupations != null) {
        this.occupations.clear();
      }

      return this;
    }

    public BuilderExample build() {
      // complicated switch statement to produce a compact properly sized immutable set omitted.
      // go to https://projectlombok.org/features/Singular-snippet.html to see it.
      Set<String> occupations = ...;
      return new BuilderExample(name, age, occupations);
    }

    @java.lang.Override
    public String toString() {
      return "BuilderExample.BuilderExampleBuilder(name = " + this.name + ", age = " + this.age + ", occupations = " + this.occupations + ")";
    }
  }
}