junit 自動化測試 取得print的內容

使用ByteArrayOutputStream 和 System.setXXX便可以簡單實現

private final ByteArrayOutputStream outContent = new ByteArrayOutputStream();
private final ByteArrayOutputStream errContent = new ByteArrayOutputStream();
private final PrintStream originalOut = System.out;
private final PrintStream originalErr = System.err;

@Before
public void setUpStreams() {
    System.setOut(new PrintStream(outContent));
    System.setErr(new PrintStream(errContent));
}

@After
public void restoreStreams() {
    System.setOut(originalOut);
    System.setErr(originalErr);
}

@Test
public void out() {
    System.out.print("hello");
    assertEquals("hello", outContent.toString());
}

@Test
public void err() {
    System.err.print("hello again");
    assertEquals("hello again", errContent.toString());
}

 

 

 

參考

https://www.it-swarm.dev/ja/java/systemoutprintln%EF%BC%88%EF%BC%89%E3%81%AEjunit%E3%83%86%E3%82%B9%E3%83%88/967276565/