add utf8 parsing test (#1404)

Author: pjfanning

src/test/java/com/fasterxml/jackson/core/read/UTF8ParsingTest.java

@@ -0,0 +1,49 @@
+package com.fasterxml.jackson.core.read;
+
+import com.fasterxml.jackson.core.JUnit5TestBase;
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.JsonToken;
+import com.fasterxml.jackson.core.TokenStreamFactory;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class UTF8ParsingTest extends JUnit5TestBase
+{
+    private TokenStreamFactory JSON_F = newStreamFactory();
+
+    final String testValue = createTestString();
+    final String INPUT_JSON = a2q("{ 'value': '" + testValue + "' }");
+
+    // https://github.com/FasterXML/jackson-dataformats-text/issues/497
+    @Test
+    public void utf8Char3Bytes() throws Exception
+    {
+        for (int mode : ALL_MODES) {
+            testIssue(JSON_F, mode, INPUT_JSON);
+        }
+    }
+    
+    private void testIssue(final TokenStreamFactory jsonF,
+                           final int mode,
+                           final String json) throws Exception
+    {
+        try (JsonParser p = createParser(jsonF, mode, json)) {
+            assertToken(JsonToken.START_OBJECT, p.nextToken());
+            assertToken(JsonToken.FIELD_NAME, p.nextToken());
+            assertEquals("value", p.currentName());
+            assertToken(JsonToken.VALUE_STRING, p.nextToken());
+            assertEquals(testValue, p.getText());
+            assertToken(JsonToken.END_OBJECT, p.nextToken());
+        }
+    }
+
+    private static String createTestString() {
+        StringBuilder sb = new StringBuilder(4001);
+        for (int i = 0; i < 4000; ++i) {
+            sb.append('a');
+        }
+        sb.append('\u5496');
+        return sb.toString();
+    }
+}