complete FileUtil test case (#587) (#595)

hippo4j-common/src/test/java/cn/hippo4j/common/toolkit/FileUtilTest.java

@@ -24,5 +24,13 @@ public class FileUtilTest {
     @Test
     public void assertReadUtf8String() {
 
+        String testText = "abcd简体繁体\uD83D\uDE04\uD83D\uDD25& *\n" +
+                "second line\n" +
+                "empty line next\n";
+
+        String testFilePath = "classpath:/test/test_utf8.txt";
+        String contentByFileUtil = FileUtil.readUtf8String(testFilePath);
+        Assert.isTrue(testText.equals(contentByFileUtil));
+
     }
 }

hippo4j-common/src/test/resources/test/test_utf8.txt

@@ -0,0 +1,3 @@
+abcd简体繁体😄🔥& *
+second line
+empty line next