Provide UT that reproduces issue protocolbuffers#3

Author: pierrick

php/tests/proto/errors/authentication_error.proto

@@ -0,0 +1,15 @@
+syntax = "proto3";
+
+import 'google/protobuf/any.proto';
+import 'google/protobuf/wrappers.proto';
+import 'google/protobuf/struct.proto';
+
+package foo.errors;
+
+message AuthenticationErrorEnum {
+  enum AuthenticationError {
+    UNSPECIFIED = 0;
+    UNKNOWN = 1;
+    AUTHENTICATION_ERROR = 2;
+  }
+}

php/tests/proto/errors/errors.proto

@@ -0,0 +1,14 @@
+syntax = "proto3";
+
+import 'google/protobuf/any.proto';
+import 'google/protobuf/wrappers.proto';
+import 'google/protobuf/struct.proto';
+import 'proto/errors/authentication_error.proto';
+
+package foo.errors;
+
+message ErrorCode {
+  oneof error_code {
+    AuthenticationErrorEnum.AuthenticationError authentication_error = 1;
+  }
+}

php/tests/test2/EncodeDecodeTest.php

@@ -5,6 +5,8 @@
 
 use Google\Protobuf\RepeatedField;
 use Google\Protobuf\GPBType;
+use Foo\Errors\ErrorCode;
+use Foo\Errors\AuthenticationErrorEnum\AuthenticationError;
 use Foo\TestInt32Value;
 use Foo\TestInt64Value;
 use Foo\TestUInt32Value;
@@ -37,6 +39,14 @@
 
 class EncodeDecodeTest extends TestBase
 {
+    public function testIssue3()
+    {
+        $m = new ErrorCode([
+            'authentication_error' => AuthenticationError::AUTHENTICATION_ERROR
+        ]);
+        $this->assertSame('{"authenticationError":"AUTHENTICATION_ERROR"}', $m->serializeToJsonString());
+    }
+
     public function testDecodeJsonSimple()
     {
         $m = new TestMessage();
@@ -326,12 +336,6 @@ public function testEncodeDecodeOneof()
 
     }
 
-    public function testJsonEncodeEnumFromInitializer()
-    {
-      $m = new TestMessage(['oneof_enum' => TestEnum::TWO]);
-      $this->assertSame('{"oneofEnum":"TWO"}', $m->serializeToJsonString());
-    }
-
     public function testJsonEncodeDecodeOneof()
     {
         $m = new TestMessage();