[core] Add OfflineDatabase.Pack unit test

include/mbgl/storage/default_file_source.hpp

@@ -200,7 +200,7 @@ public:
      * Sets whether packing the database file occurs automatically after an offline
      * region is deleted (deleteOfflineRegion()) or the ambient cache is cleared
      * (clearAmbientCache()).
-     * 
+     *
      * By default, packing is enabled. If disabled, disk space will not be freed
      * after resources are removed unless packDatabase() is explicitly called.
      */
@@ -223,8 +223,8 @@ public:
     /*
      * Erase resources from the ambient cache, freeing storage space.
      *
-     * Erases the ambient cache, freeing resources. 
-     * 
+     * Erases the ambient cache, freeing resources.
+     *
      * Note that this operation can be potentially slow if packing the database
      * occurs automatically (see runPackDatabaseAutomatically() and packDatabase()).
      *

test/storage/offline_database.test.cpp

@@ -733,6 +733,36 @@ TEST(OfflineDatabase, TEST_REQUIRES_WRITE(DeleteRegion)) {
     EXPECT_EQ(0u, log.uncheckedCount());
 }
 
+TEST(OfflineDatabase, TEST_REQUIRES_WRITE(Pack)) {
+    FixtureLog log;
+    deleteDatabaseFiles();
+
+    OfflineDatabase db(filename);
+    size_t initialSize = util::read_file(filename).size();
+    db.runPackDatabaseAutomatically(false);
+
+    Response response;
+    response.data = randomString(.5 * 1024 * 1024);
+
+    for (unsigned i = 0; i < 50; ++i) {
+        const Resource tile = Resource::tile("mapbox://tile_" + std::to_string(i), 1, 0, 0, 0, Tileset::Scheme::XYZ);
+        db.put(tile, response);
+
+        const Resource style = Resource::style("mapbox://style_" + std::to_string(i));
+        db.put(style, response);
+    }
+    size_t populatedSize = util::read_file(filename).size();
+    ASSERT_GT(populatedSize, initialSize);
+
+    db.clearAmbientCache();
+    EXPECT_EQ(populatedSize, util::read_file(filename).size());
+    EXPECT_EQ(0u, log.uncheckedCount());
+
+    db.pack();
+    EXPECT_EQ(initialSize, util::read_file(filename).size());
+    EXPECT_EQ(0u, log.uncheckedCount());
+}
+
 TEST(OfflineDatabase, MapboxTileLimitExceeded) {
     FixtureLog log;