diff --git a/gson/src/test/java/com/google/gson/JsonPrimitiveTest.java b/gson/src/test/java/com/google/gson/JsonPrimitiveTest.java
index b5af6a81..cdd4fdb6 100644
--- a/gson/src/test/java/com/google/gson/JsonPrimitiveTest.java
+++ b/gson/src/test/java/com/google/gson/JsonPrimitiveTest.java
@@ -108,6 +108,9 @@ public class JsonPrimitiveTest extends TestCase {
     assertTrue(json.isString());
     assertEquals('z', json.getAsCharacter());
     assertEquals("z", json.getAsString());
+
+    json = new JsonPrimitive(true);
+    assertEquals("true", json.getAsString());
   }
 
   public void testExponential() throws Exception {
diff --git a/gson/src/test/java/com/google/gson/internal/bind/JsonTreeWriterTest.java b/gson/src/test/java/com/google/gson/internal/bind/JsonTreeWriterTest.java
index cc04dbc3..094f04bd 100644
--- a/gson/src/test/java/com/google/gson/internal/bind/JsonTreeWriterTest.java
+++ b/gson/src/test/java/com/google/gson/internal/bind/JsonTreeWriterTest.java
@@ -120,6 +120,34 @@ public final class JsonTreeWriterTest extends TestCase {
     assertEquals(JsonNull.INSTANCE, writer.get());
   }
 
+  public void testBeginArray() throws Exception {
+    JsonTreeWriter writer = new JsonTreeWriter();
+    assertEquals(writer, writer.beginArray());
+  }
+
+  public void testBeginObject() throws Exception {
+    JsonTreeWriter writer = new JsonTreeWriter();
+    assertEquals(writer, writer.beginObject());
+  }
+
+  public void testValueString() throws Exception {
+    JsonTreeWriter writer = new JsonTreeWriter();
+    String n = "as";
+    assertEquals(writer, writer.value(n));
+  }
+
+  public void testBoolValue() throws Exception {
+    JsonTreeWriter writer = new JsonTreeWriter();
+    boolean bool = true;
+    assertEquals(writer, writer.value(bool));
+  }
+
+  public void testBoolMaisValue() throws Exception {
+    JsonTreeWriter writer = new JsonTreeWriter();
+    Boolean bool = true;
+    assertEquals(writer, writer.value(bool));
+  }
+
   public void testLenientNansAndInfinities() throws IOException {
     JsonTreeWriter writer = new JsonTreeWriter();
     writer.setLenient(true);
diff --git a/gson/src/test/java/com/google/gson/internal/bind/util/ISO8601UtilsTest.java b/gson/src/test/java/com/google/gson/internal/bind/util/ISO8601UtilsTest.java
new file mode 100644
index 00000000..10b7b5e0
--- /dev/null
+++ b/gson/src/test/java/com/google/gson/internal/bind/util/ISO8601UtilsTest.java
@@ -0,0 +1,101 @@
+package com.google.gson.internal.bind.util;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import java.text.ParseException;
+import java.text.ParsePosition;
+import java.util.*;
+
+import static org.junit.Assert.assertEquals;
+
+public class ISO8601UtilsTest {
+
+    @Rule
+    public final ExpectedException exception = ExpectedException.none();
+
+    @Test
+    public void testDateFormatString() {
+        Date date = new GregorianCalendar(2018, Calendar.JUNE, 25).getTime();
+        String dateStr = ISO8601Utils.format(date);
+        String expectedDate = "2018-06-25";
+        assertEquals(expectedDate, dateStr.substring(0, expectedDate.length()));
+    }
+
+    @Test
+    public void testDateFormatWithMilliseconds() {
+        long time = 1530209176870L;
+        Date date = new Date(time);
+        String dateStr = ISO8601Utils.format(date, true);
+        String expectedDate = "2018-06-28T18:06:16.870Z";
+        assertEquals(expectedDate, dateStr);
+    }
+
+    @Test
+    public void testDateFormatWithTimezone() {
+        long time = 1530209176870L;
+        Date date = new Date(time);
+        String dateStr = ISO8601Utils.format(date, true, TimeZone.getTimeZone("Brazil/East"));
+        String expectedDate = "2018-06-28T15:06:16.870-03:00";
+        assertEquals(expectedDate, dateStr);
+    }
+
+    @Test
+    public void testDateParseWithDefaultTimezone() throws ParseException {
+        String dateStr = "2018-06-25";
+        Date date = ISO8601Utils.parse(dateStr, new ParsePosition(0));
+        Date expectedDate = new GregorianCalendar(2018, Calendar.JUNE, 25).getTime();
+        assertEquals(expectedDate, date);
+    }
+
+    @Test
+    public void testDateParseWithTimezone() throws ParseException {
+        TimeZone defaultTimeZone = TimeZone.getDefault();
+        TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
+        Locale defaultLocale = Locale.getDefault();
+        Locale.setDefault(Locale.US);
+        try {
+            String dateStr = "2018-06-25T00:00:00-03:00";
+            Date date = ISO8601Utils.parse(dateStr, new ParsePosition(0));
+            Date expectedDate = new GregorianCalendar(2018, Calendar.JUNE, 25, 3, 0).getTime();
+            assertEquals(expectedDate, date);
+        } finally {
+            TimeZone.setDefault(defaultTimeZone);
+            Locale.setDefault(defaultLocale);
+        }
+    }
+
+    @Test
+    public void testDateParseSpecialTimezone() throws ParseException {
+        TimeZone defaultTimeZone = TimeZone.getDefault();
+        TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
+        Locale defaultLocale = Locale.getDefault();
+        Locale.setDefault(Locale.US);
+        try {
+            String dateStr = "2018-06-25T00:02:00-02:58";
+            Date date = ISO8601Utils.parse(dateStr, new ParsePosition(0));
+            Date expectedDate = new GregorianCalendar(2018, Calendar.JUNE, 25, 3, 0).getTime();
+            assertEquals(expectedDate, date);
+        } finally {
+            TimeZone.setDefault(defaultTimeZone);
+            Locale.setDefault(defaultLocale);
+        }
+    }
+
+    @Test
+    public void testDateParseInvalidTime() throws ParseException {
+        TimeZone defaultTimeZone = TimeZone.getDefault();
+        TimeZone.setDefault(TimeZone.getTimeZone("UTC"));
+        Locale defaultLocale = Locale.getDefault();
+        Locale.setDefault(Locale.US);
+        try {
+            String dateStr = "2018-06-25T61:60:62-03:00";
+            exception.expect(ParseException.class);
+            ISO8601Utils.parse(dateStr, new ParsePosition(0));
+        } finally {
+            TimeZone.setDefault(defaultTimeZone);
+            Locale.setDefault(defaultLocale);
+        }
+    }
+}