Add unit tests for me.zhengjie.utils.FileUtil

These tests were written using Diffblue Cover.

eladmin-common/src/test/java/me/zhengjie/utils/FileUtilTest.java

+package me.zhengjie.utils;
+
+import org.junit.Test;
+import org.springframework.mock.web.MockMultipartFile;
+
+import static org.junit.Assert.*;
+import static me.zhengjie.utils.FileUtil.*;
+
+public class FileUtilTest {
+
+    @Test
+    public void testToFile() {
+        long retval = toFile(new MockMultipartFile("foo", (byte[]) null)).getTotalSpace();
+        assertEquals(500695072768L, retval);
+    }
+
+    @Test
+    public void testGetExtensionName() {
+        assertEquals("foo", getExtensionName("foo"));
+        assertEquals("exe", getExtensionName("bar.exe"));
+    }
+
+    @Test
+    public void testGetFileNameNoEx() {
+        assertEquals("foo", getFileNameNoEx("foo"));
+        assertEquals("bar", getFileNameNoEx("bar.txt"));
+    }
+
+    @Test
+    public void testGetSize() {
+        assertEquals("1000B   ", getSize(1000));
+        assertEquals("1.00KB   ", getSize(1024));
+        assertEquals("1.00MB   ", getSize(1048576));
+        assertEquals("1.00GB   ", getSize(1073741824));
+    }
+}