junit3为何只能跑public void testXXX()声明方法

junit完整生命周期时序图

在图中第2步调用TestSuite构造方法时，代码如下：

	 public TestSuite(final Class theClass) {
		fName= theClass.getName();
		try {
			getTestConstructor(theClass); // Avoid generating multiple error messages
		} catch (NoSuchMethodException e) {
			addTest(warning("Class "+theClass.getName()+" has no public constructor TestCase(String name) or TestCase()"));
			return;
		}

		if (!Modifier.isPublic(theClass.getModifiers())) {
			addTest(warning("Class "+theClass.getName()+" is not public"));
			return;
		}

		Class superClass= theClass;
		Vector names= new Vector();
		while (Test.class.isAssignableFrom(superClass)) {
			Method[] methods= superClass.getDeclaredMethods();
			for (int i= 0; i < methods.length; i++) {
				addTestMethod(methods[i], names, theClass);
			}
			superClass= superClass.getSuperclass();
		}
		if (fTests.size() == 0)
			addTest(warning("No tests found in "+theClass.getName()));
	}

addTestMethod()方法代码如下：

	private void addTestMethod(Method m, Vector names, Class theClass) {
		String name= m.getName();
		if (names.contains(name))
			return;
		if (! isPublicTestMethod(m)) {
			if (isTestMethod(m))
				addTest(warning("Test method isn't public: "+m.getName()));
			return;
		}
		names.addElement(name);
		addTest(createTest(theClass, name));
	}

isTestMethod()方法代码如下：

	private boolean isTestMethod(Method m) {
		String name= m.getName();
		Class[] parameters= m.getParameterTypes();
		Class returnType= m.getReturnType();
		return parameters.length == 0 && name.startsWith("test") && returnType.equals(Void.TYPE);
	 }

最后一行代码给出了对test方法声明所做的限制。