這并不是要成為技術含量很高的職位。 這篇文章的目的是為您提供一些指導，以使您的JUnit測試生活更加輕松，使您能夠在幾分鐘內編寫復雜的測試場景，并具有易于閱讀的測試優勢。

單元測試中有兩個主要部分，需要編寫許多引導程序代碼：

• 設置部分：構建初始狀態需要構建將被饋送到SUT（被測系統）的初始對象
• 斷言部分：構造輸出對象的所需圖像，并僅對所需數據進行斷言。

為了降低構建用于測試的對象的復雜性，我建議在以下解釋中使用Builder模式：

這是域對象：

public class Employee {private int id;private String name;private Department department;//setters, getters, hashCode, equals, toString methods

此域對象的生成器如下所示：

public class EmployeeBuilder {private Employee employee;public EmployeeBuilder() {employee = new Employee();}public static EmployeeBuilder defaultValues() {return new EmployeeBuilder();}public static EmployeeBuilder clone(Employee toClone) {EmployeeBuilder builder = defaultValues();builder.setId(toClone.getId());builder.setName(toClone.getName());builder.setDepartment(toClone.getDepartment());return builder;}public static EmployeeBuilder random() {EmployeeBuilder builder = defaultValues();builder.setId(getRandomInteger(0, 1000));builder.setName(getRandomString(20));builder.setDepartment(Department.values()[getRandomInteger(0, Department.values().length - 1)]);return builder;}public EmployeeBuilder setId(int id) {employee.setId(id);return this;}public EmployeeBuilder setName(String name) {employee.setName(name);return this;}public EmployeeBuilder setDepartment(Department dept) {employee.setDepartment(dept);return this;}public Employee build() {return employee;}
}

如您所見，我們有一些工廠方法：

public static EmployeeBuilder defaultValues()public static EmployeeBuilder clone(Employee toClone)public static EmployeeBuilder random()

這些方法返回不同的構建器：

• defaultValues：每個字段的一些硬編碼值（或Java默認值-當前實現）
• clone：將獲取初始對象中的所有值，并使您可以更改其中一些值
• random：將為每個字段生成隨機值。 當您有很多字段在測試中不需要時非常有用，但是您需要將它們初始化。 getRandom *方法是在另一個類中靜態定義的。

您可以添加其他方法來根據需要初始化構建器。

此外，構建器還可以處理一些不那么容易構建和更改的對象。 例如，讓我們稍微更改Employee對象，使其不可變：

public class Employee {private final int id;private final String name;private final Department department;...
}

現在，我們失去了按需更改字段的可能性。 但是使用以下形式的構建器，我們可以在構造對象時重新獲得這種可能性：

public class ImmutableEmployeeBuilder {private int id;private String name;private Department department;public ImmutableEmployeeBuilder() {}public static ImmutableEmployeeBuilder defaultValues() {return new ImmutableEmployeeBuilder();}public static ImmutableEmployeeBuilder clone(Employee toClone) {ImmutableEmployeeBuilder builder = defaultValues();builder.setId(toClone.getId());builder.setName(toClone.getName());builder.setDepartment(toClone.getDepartment());return builder;}public static ImmutableEmployeeBuilder random() {ImmutableEmployeeBuilder builder = defaultValues();builder.setId(getRandomInteger(0, 1000));builder.setName(getRandomString(20));builder.setDepartment(Department.values()[getRandomInteger(0, Department.values().length - 1)]);return builder;}public ImmutableEmployeeBuilder setId(int id) {this.id = id;return this;}public ImmutableEmployeeBuilder setName(String name) {this.name = name;return this;}public ImmutableEmployeeBuilder setDepartment(Department dept) {this.department = dept;return this;}public ImmutableEmployee build() {return new ImmutableEmployee(id, name, department);}
}

當我們難以構造對象或需要更改最終字段時，這非常有用。

這是它的最終結果：

沒有建設者：

@Testpublic void changeRoleTestWithoutBuilders() {// building the initial stateEmployee employee = new Employee();employee.setId(1);employee.setDepartment(Department.DEVELOPEMENT);employee.setName("John Johnny");// testing the SUTEmployeeManager employeeManager = new EmployeeManager();employeeManager.changeRole(employee, Department.MANAGEMENT);// building the expectationsEmployee expectedEmployee = new Employee();expectedEmployee.setId(employee.getId());expectedEmployee.setDepartment(Department.MANAGEMENT);expectedEmployee.setName(employee.getName());// assertionsassertThat(employee, is(expectedEmployee));}

與建設者：

@Testpublic void changeRoleTestWithBuilders() {// building the initial stateEmployee employee = EmployeeBuilder.defaultValues().setId(1).setName("John Johnny").setDepartment(Department.DEVELOPEMENT).build();// building the expectationsEmployee expectedEmployee = EmployeeBuilder.clone(employee).setDepartment(Department.MANAGEMENT).build();// testing the SUTEmployeeManager employeeManager = new EmployeeManager();employeeManager.changeRole(employee, Department.MANAGEMENT);// assertionsassertThat(employee, is(expectedEmployee));}

如您所見，測試的大小要小得多，對象的構造也變得更加簡單（如果代碼格式更好，也會更好）。 如果您具有更復雜的域對象（在實際應用程序中，尤其是在遺留代碼中），則差異更大。

玩得開心！

參考：來自Java出現日歷博客的JCG合作伙伴 Stefan Bulzan 在JUnit測試中使用了Builder模式 。

翻譯自: https://www.javacodegeeks.com/2012/12/using-builder-pattern-in-junit-tests.html