pytest: test the db hook plugin.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/plugins/dblog.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+"""This plugin is used to check that db_write calls are working correctly.
+"""
+from lightning import Plugin, RpcError
+import sqlite3
+
+plugin = Plugin()
+plugin.sqlite_pre_init_cmds = []
+plugin.initted = False
+
+
+@plugin.init()
+def init(configuration, options, plugin):
+    if not plugin.get_option('dblog-file'):
+        raise RpcError("No dblog-file specified")
+    plugin.conn = sqlite3.connect(plugin.get_option('dblog-file'),
+                                  isolation_level=None)
+    plugin.log("replaying pre-init data:")
+    for c in plugin.sqlite_pre_init_cmds:
+        plugin.conn.execute(c)
+        plugin.log("{}".format(c))
+    plugin.initted = True
+    plugin.log("initialized")
+
+
+@plugin.hook('db_write')
+def db_write(plugin, writes):
+    if not plugin.initted:
+        plugin.log("deferring {} commands".format(len(writes)))
+        plugin.sqlite_pre_init_cmds += writes
+    else:
+        for c in writes:
+            plugin.conn.execute(c)
+            plugin.log("{}".format(c))
+    return True
+
+
+plugin.add_option('dblog-file', None, 'The db file to create.')
+plugin.run()