Add (failing) test for 2230

src/test/java/com/fasterxml/jackson/databind/ser/jdk/NumberSerTest.java

@@ -5,6 +5,7 @@
 
 import com.fasterxml.jackson.annotation.JsonFormat;
 import com.fasterxml.jackson.annotation.JsonProperty;
+
 import com.fasterxml.jackson.databind.BaseMapTest;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.annotation.JsonSerialize;
@@ -55,7 +56,10 @@ static class BigIntegerAsString {
 
     static class BigDecimalAsString {
         @JsonFormat(shape=JsonFormat.Shape.STRING)
-        public BigDecimal value = BigDecimal.valueOf(0.25);
+        public BigDecimal value;
+
+        public BigDecimalAsString() { this(BigDecimal.valueOf(0.25)); }
+        public BigDecimalAsString(BigDecimal v) { value = v; }
     }
 
     static class NumberWrapper {

src/test/java/com/fasterxml/jackson/failing/BigDecimalPlain2230Test.java

@@ -0,0 +1,37 @@
+package com.fasterxml.jackson.failing;
+
+import java.math.BigDecimal;
+
+import com.fasterxml.jackson.annotation.JsonFormat;
+
+import com.fasterxml.jackson.core.StreamWriteFeature;
+
+import com.fasterxml.jackson.databind.*;
+
+public class BigDecimalPlain2230Test extends BaseMapTest
+{
+    static class BigDecimalAsString {
+        @JsonFormat(shape=JsonFormat.Shape.STRING)
+        public BigDecimal value;
+
+        public BigDecimalAsString() { this(BigDecimal.valueOf(0.25)); }
+        public BigDecimalAsString(BigDecimal v) { value = v; }
+    }
+
+    private final ObjectMapper MAPPER = objectMapper();
+
+    public void testBigIntegerAsPlainTest() throws Exception
+    {
+        final String NORM_VALUE = "0.0000000005";
+        final BigDecimal BD_VALUE = new BigDecimal(NORM_VALUE);
+        final BigDecimalAsString INPUT = new BigDecimalAsString(BD_VALUE);
+        // by default, use the default `toString()`
+        assertEquals("{\"value\":\""+BD_VALUE.toString()+"\"", MAPPER.writeValueAsString(INPUT));
+
+        // but can force to "plain" notation
+        final ObjectMapper m = jsonMapperBuilder()
+            .enable(StreamWriteFeature.WRITE_BIGDECIMAL_AS_PLAIN)
+            .build();
+        assertEquals("{\"value\":\""+NORM_VALUE+"\"", m.writeValueAsString(INPUT));
+    }
+}