在JunitJava中应该有另一行时，出现Scanner.NextLine上的NoSuchElementException

问题描述

我正在写一个命令行游戏，用户在其中输入命令。这是用户界面的类：

public class UserInterface {

  private int loops = 0;
  private boolean gameEnded;
  private String inputLine;
  private String[] commands;

  public void gameLoop(){
    Scanner input = new Scanner(system.in);
    gameEnded = false;


    while(!gameEnded){
      loops++;
      System.out.print("> ");
      inputLine = input.nextLine().toLowerCase();
      commands = inputLine.split(" ");
      if(commands[0].equals("quit") || commands[0].equals("exit")){
        gameEnded = true;
        continue;
      }
    }
  }

  @Override
  public String toString(){
    return "Loops: " + loops;
  }


}

我试图通过使用ByteArrayInputStreams将输入字符串重定向到System。来测试Junit中的命令退出，类似于此处的示例：JUnit: How to simulate System.in testing?

这是我的测试班：

public class UITest {

    UserInterface ui;
    private ByteArrayInputStream testIn;
    private final InputStream systemIn = system.in;


    /**
     * Changes system.in into a given string
     * @param data
     */
    private void provideInput(String data) {
        testIn = new ByteArrayInputStream(data.getBytes());
        System.setIn(testIn);
    }
    @Before
    public void setUp() {
        ui = new UserInterface();
    }

    @Test
    public void testQuit(){
        String input = "quit\r\n";
        provideInput(input);
        ui.gameLoop();
        System.out.println(input);

        assertEquals("Loops: 1",ui.toString());

    }

    @Test
    public void testQuitWithSpaces(){
        String input = "apple\r\n";
        provideInput(input);

        ui.gameLoop();
        System.out.println(input);

        assertEquals("Loops: 1",ui.toString());

    }

我的第一个测试testQuit（）运行得很好。但是，当我运行以下测试testQuitWithSpaces（）时，我什至没有得到无限的while循环，我只会遇到以下错误：

java.util.NoSuchElementException: No line found

    at java.base/java.util.Scanner.nextLine(Scanner.java:1651)
    at package.UserInterface.gameLoop(UserInterface.java:24)
    at package.UITest.testQuitWithSpaces(AdventureTest.java:54)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:567)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runchild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runchild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runchildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
    at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
    at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:220)
    at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:53)


Process finished with exit code -1

解决方法

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