KERNEL-1197 新增两个单元测试，添加了一个返回值说明，删除掉了被标记为Open的BaseFormula

src/main/java/com/fanruan/api/base/BaseFormula.java

@@ -1,4 +0,0 @@
-package com.fanruan.api.base;
-
-public abstract class BaseFormula extends com.fr.base.BaseFormula {
-}

src/main/java/com/fanruan/api/util/CellKit.java

@@ -14,7 +14,7 @@ public class CellKit {
      * @param style 绘制image的style
      * @param width 绘制image的宽
      * @param height 绘制image的高
-     * @return
+     * @return 返回宽为width，高为height,类型为TYPE_4BYTE_ABGR的image
      */
     public static Image value2Image(Object value, int resolution, Style style, int width, int height){
         return CellUtils.value2Image(value, resolution, style, width, height);

src/test/java/com/fanruan/api/util/CellKitTest.java

@@ -0,0 +1,22 @@
+package com.fanruan.api.util;
+
+import com.fr.base.Style;
+import com.fr.plugin.present.fun.StarPainter;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.awt.*;
+
+import static org.junit.Assert.*;
+
+public class CellKitTest {
+
+    @Test
+    public void value2Image() {
+        StarPainter star = new StarPainter(1);
+        Style style = Style.getInstance();
+        Image image = CellKit.value2Image(star, 1, style, 30, 50);
+        Assert.assertEquals(30, image.getWidth(null));
+        Assert.assertEquals(50, image.getHeight(null));
+    }
+}

src/test/java/com/fanruan/api/util/StableKitTest.java

@@ -0,0 +1,19 @@
+package com.fanruan.api.util;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class StableKitTest {
+
+    @Test
+    public void canBeFormula() {
+        String s1 = "=1";
+        String s2 = "=a+b+";
+        String s3 = "ppp";
+        Assert.assertTrue(StableKit.canBeFormula(s1));
+        Assert.assertTrue(StableKit.canBeFormula(s2));
+        Assert.assertFalse(StableKit.canBeFormula(s3));
+    }
+}