如何为 IOException 编写 junit 测试用例

Question

我想在 JUNIT 测试中检查 IOException 类。这是我的代码：

public void loadProperties(String path) throws IOException {
  InputStream in = this.getClass().getResourceAsStream(path);
  Properties properties = new Properties();
  properties.load(in);
  this.foo = properties.getProperty("foo");
  this.foo1 = properties.getProperty("foo1");
}

当我尝试给出错误的属性文件路径时，它给出了 NullPointerException。我想对其进行 IOException 和 Junit 测试。非常感谢您的帮助。

Answer 1

不确定我们如何IOException使用当前的实现来模拟，但是如果您以如下方式重构代码：

public void loadProperties(String path) throws IOException {
    InputStream in = this.getClass().getResourceAsStream(path);
    loadProperties(in);
}

public void loadProperties(InputStream in) throws IOException {
    Properties properties = new Properties();
    properties.load(in);
    this.foo = properties.getProperty("foo");
    this.foo1 = properties.getProperty("foo1");
}

并创建一个模拟的 InputStream，如下所示：

package org.uniknow.test;

import static org.easymock.EasyMock.createMock;
import static org.easymock.EasyMock.expect;
import static org.easymock.EasyMock.replay;

public class TestLoadProperties {

   @test(expected="IOException.class")
   public void testReadProperties() throws IOException {
       InputStream in = createMock(InputStream.class);
       expect(in.read()).andThrow(IOException.class);
       replay(in);

       // Instantiate instance in which properties are loaded

      x.loadProperties(in);
   }
} 

警告：上面的代码是即时创建的，没有通过编译进行验证，因此可能存在语法错误。