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+# 2012 October 13
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+# The tests in this file verify that if an empty database (zero bytes in 
+# size) is used as the source of a backup operation, the final destination
+# database is one page in size.
+#
+# The destination must consist of at least one page as truncating a 
+# database file to zero bytes is equivalent to resetting the database
+# schema cookie and change counter. Doing that could cause other clients
+# to become confused and continue using out-of-date cache data.
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix backup4
+
+#-------------------------------------------------------------------------
+# At one point this test was failing because [db] was using an out of
+# date schema in test case 1.2.
+#
+do_execsql_test 1.0 {
+  CREATE TABLE t1(x, y, UNIQUE(x, y));
+  INSERT INTO t1 VALUES('one', 'two');
+  SELECT * FROM t1 WHERE x='one';
+  PRAGMA integrity_check;
+} {one two ok}
+
+do_test 1.1 {
+  sqlite3 db1 :memory:
+  db1 backup test.db
+  sqlite3 db1 test.db
+  db1 eval {
+    CREATE TABLE t1(x, y);
+    INSERT INTO t1 VALUES('one', 'two');
+  }
+  db1 close
+} {}
+
+do_execsql_test 1.2 {
+  SELECT * FROM t1 WHERE x='one';
+  PRAGMA integrity_check;
+} {one two ok}
+
+db close
+forcedelete test.db
+forcedelete test.db2
+sqlite3 db test.db
+
+#-------------------------------------------------------------------------
+# Test that if the source is zero bytes, the destination database 
+# consists of a single page only.
+#
+do_execsql_test 2.1 {
+  CREATE TABLE t1(a, b);
+  CREATE INDEX i1 ON t1(a, b);
+}
+do_test 2.2 { file size test.db } [expr $AUTOVACUUM ? 4096 : 3072]
+
+do_test 2.3 {
+  sqlite3 db1 test.db2
+  db1 backup test.db
+  db1 close
+  file size test.db
+} {1024}
+
+do_test 2.4 { file size test.db2 } 0
+
+db close
+forcedelete test.db
+forcedelete test.db2
+sqlite3 db test.db
+
+#-------------------------------------------------------------------------
+# Test that if the destination has a page-size larger than the implicit
+# page-size of the source, the final destination database still consists
+# of a single page.
+#
+do_execsql_test 3.1 {
+  PRAGMA page_size = 4096;
+  CREATE TABLE t1(a, b);
+  CREATE INDEX i1 ON t1(a, b);
+}
+do_test 3.2 { file size test.db } [expr $AUTOVACUUM ? 16384 : 12288]
+
+do_test 3.3 {
+  sqlite3 db1 test.db2
+  db1 backup test.db
+  db1 close
+  file size test.db
+} {1024}
+
+do_test 3.4 { file size test.db2 } 0
+
+finish_test
+