diff --git a/samples/client/petstore/java/src/test/java/io/swagger/client/ApiInvokerTest.java b/samples/client/petstore/java/src/test/java/io/swagger/client/ApiInvokerTest.java
new file mode 100644
index 00000000000..ec5a54c2aa9
--- /dev/null
+++ b/samples/client/petstore/java/src/test/java/io/swagger/client/ApiInvokerTest.java
@@ -0,0 +1,42 @@
+package io.swagger.client;
+
+import static org.junit.Assert.*;
+import org.junit.*;
+
+public class ApiInvokerTest {
+  @Test
+  public void testSelectHeaderAccept() {
+    String[] accepts = { "APPLICATION/JSON", "APPLICATION/XML" };
+    assertEquals("application/json", ApiInvoker.selectHeaderAccept(accepts));
+
+    accepts = new String[] { "application/json", "application/xml" };
+    assertEquals("application/json", ApiInvoker.selectHeaderAccept(accepts));
+
+    accepts = new String[] { "application/xml", "application/json" };
+    assertEquals("application/json", ApiInvoker.selectHeaderAccept(accepts));
+
+    accepts = new String[] { "text/plain", "application/xml" };
+    assertEquals("text/plain,application/xml", ApiInvoker.selectHeaderAccept(accepts));
+
+    accepts = new String[] { };
+    assertEquals("application/json", ApiInvoker.selectHeaderAccept(accepts));
+  }
+
+  @Test
+  public void testSelectHeaderContentType() {
+    String[] contentTypes = { "APPLICATION/JSON", "APPLICATION/XML" };
+    assertEquals("application/json", ApiInvoker.selectHeaderContentType(contentTypes));
+
+    contentTypes = new String[] { "application/json", "application/xml" };
+    assertEquals("application/json", ApiInvoker.selectHeaderContentType(contentTypes));
+
+    contentTypes = new String[] { "application/xml", "application/json" };
+    assertEquals("application/json", ApiInvoker.selectHeaderContentType(contentTypes));
+
+    contentTypes = new String[] { "text/plain", "application/xml" };
+    assertEquals("text/plain", ApiInvoker.selectHeaderContentType(contentTypes));
+
+    contentTypes = new String[] { };
+    assertEquals("application/json", ApiInvoker.selectHeaderContentType(contentTypes));
+  }
+}
diff --git a/samples/client/petstore/java/src/test/java/io/swagger/client/StringUtilTest.java b/samples/client/petstore/java/src/test/java/io/swagger/client/StringUtilTest.java
new file mode 100644
index 00000000000..a9abfb03290
--- /dev/null
+++ b/samples/client/petstore/java/src/test/java/io/swagger/client/StringUtilTest.java
@@ -0,0 +1,32 @@
+package io.swagger.client;
+
+import static org.junit.Assert.*;
+import org.junit.*;
+
+public class StringUtilTest {
+  @Test
+  public void testContainsIgnoreCase() {
+    assertTrue(StringUtil.containsIgnoreCase(new String[]{ "abc" }, "abc"));
+    assertTrue(StringUtil.containsIgnoreCase(new String[]{ "abc" }, "ABC"));
+    assertTrue(StringUtil.containsIgnoreCase(new String[]{ "ABC" }, "abc"));
+    assertTrue(StringUtil.containsIgnoreCase(new String[]{ null, "abc" }, "ABC"));
+    assertTrue(StringUtil.containsIgnoreCase(new String[]{ null, "abc" }, null));
+
+    assertFalse(StringUtil.containsIgnoreCase(new String[]{ "abc" }, "def"));
+    assertFalse(StringUtil.containsIgnoreCase(new String[]{ }, "ABC"));
+    assertFalse(StringUtil.containsIgnoreCase(new String[]{ }, null));
+  }
+
+  @Test
+  public void testJoin() {
+    String[] array = { "aa", "bb", "cc" };
+    assertEquals("aa,bb,cc", StringUtil.join(array, ","));
+    assertEquals("aa, bb, cc", StringUtil.join(array, ", "));
+    assertEquals("aabbcc", StringUtil.join(array, ""));
+    assertEquals("aa bb cc", StringUtil.join(array, " "));
+    assertEquals("aa\nbb\ncc", StringUtil.join(array, "\n"));
+
+    assertEquals("", StringUtil.join(new String[]{ }, ","));
+    assertEquals("abc", StringUtil.join(new String[]{ "abc" }, ","));
+  }
+}