Disentangle fpdfsave_embeddertest's FPDF_FILEWRITE, use gmock matchers.

fpdfsdk/src/fpdfedit_embeddertest.cpp

Index: fpdfsdk/src/fpdfedit_embeddertest.cpp
diff --git a/fpdfsdk/src/fpdfedit_embeddertest.cpp b/fpdfsdk/src/fpdfedit_embeddertest.cpp
index 9db948cd1f23b5f3628c6755f8da45c2473527f3..ce022fa91cc2a2ff977ec326e2d530af49239e3b 100644
--- a/fpdfsdk/src/fpdfedit_embeddertest.cpp
+++ b/fpdfsdk/src/fpdfedit_embeddertest.cpp
@@ -5,14 +5,18 @@
 #include "public/fpdf_edit.h"
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
+#include "testing/gmock/include/gmock/gmock-matchers.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "testing/test_support.h"
 
-class FPDFEditEmbeddertest : public EmbedderTest {};
+class FPDFEditEmbeddertest : public EmbedderTest, public TestSaver {};
 
 TEST_F(FPDFEditEmbeddertest, EmptyCreation) {
   EXPECT_TRUE(CreateEmptyDocument());
   FPDF_PAGE page = FPDFPage_New(document(), 1, 640.0, 480.0);
   EXPECT_NE(nullptr, page);
   EXPECT_TRUE(FPDFPage_GenerateContent(page));
+  EXPECT_TRUE(FPDF_SaveAsCopy(document(), this, 0));
+  EXPECT_THAT(GetString(), testing::StartsWith("%PDF-1.7\r\n"));
   FPDFPage_Delete(document(), 1);
 }