add testcase.

src/test/java/com/alibaba/json/bvt/parser/deser/floatDeser/EmptStringTest.java

@@ -0,0 +1,18 @@
+package com.alibaba.json.bvt.parser.deser.floatDeser;
+
+import com.alibaba.fastjson.JSON;
+import junit.framework.TestCase;
+
+/**
+ * Created by wenshao on 14/04/2017.
+ */
+public class EmptStringTest extends TestCase {
+    public void test_emptyString() throws Exception {
+        Model model = JSON.parseObject("{\"value\":\"\"}", Model.class);
+        assertEquals(0f, model.value);
+    }
+
+    public static class Model {
+        public float value;
+    }
+}