Here you can find the source of assertTrue(boolean b, String msgTemplate, Object... params)
public static void assertTrue(boolean b, String msgTemplate, Object... params)
//package com.java2s; //License from project: Apache License public class Main { public static void assertTrue(boolean b, String msgTemplate, Object... params) { if (!b) { throw new IllegalArgumentException(getMsg("Assert fail: not true.", msgTemplate, params)); }//w w w . jav a2 s. c o m } private static String getMsg(String defaultMsg, String msgTemplate, Object[] params) { return msgTemplate == null ? defaultMsg : String.format(msgTemplate, params); } }