Add failing test for #307 (#318)

datetime/src/test/java/com/fasterxml/jackson/datatype/jsr310/failing/InstanceViaBigDecimal307Test.java

@@ -0,0 +1,42 @@
+package com.fasterxml.jackson.datatype.jsr310.failing;
+
+import java.time.Instant;
+
+import org.junit.Test;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jsr310.ModuleTestBase;
+
+import static org.junit.Assert.assertEquals;
+
+// [modules-java8#307]: Loss of precision via JsonNode for BigDecimal-valued
+// things (like Instant)
+public class InstanceViaBigDecimal307Test extends ModuleTestBase
+{
+    static class Wrapper307 {
+        public Instant value;
+
+        public Wrapper307(Instant v) { value = v; }
+        protected Wrapper307() { }
+    }
+
+    private final Instant ISSUED_AT = Instant.ofEpochSecond(1234567890).plusNanos(123456789);
+
+    private ObjectMapper MAPPER = newMapper();
+
+    @Test
+    public void instantViaReadValue() throws Exception {
+         String serialized = MAPPER.writeValueAsString(new Wrapper307(ISSUED_AT));
+         Wrapper307 deserialized = MAPPER.readValue(serialized, Wrapper307.class);
+         assertEquals(ISSUED_AT, deserialized.value);
+    }
+
+    @Test
+    public void instantViaReadTree() throws Exception {
+        String serialized = MAPPER.writeValueAsString(new Wrapper307(ISSUED_AT));
+        JsonNode tree = MAPPER.readTree(serialized);
+        Wrapper307 deserialized = MAPPER.treeToValue(tree, Wrapper307.class);
+        assertEquals(ISSUED_AT, deserialized.value);
+    }
+}