Triggers and foreign key execution order in SQL

A problem with triggers in SQL.

box.sql.execute("CREATE TABLE b1 (s1 INT PRIMARY KEY, s2 INT);")
box.sql.execute("CREATE TABLE b2 (s1 INT PRIMARY KEY, s2 INT, FOREIGN KEY (s2)    REFERENCES b1 (s1));")
box.sql.execute("CREATE TABLE b3 (s1 VARCHAR(100) PRIMARY KEY);")
box.sql.execute("PRAGMA foreign_keys=on;")
box.sql.execute("CREATE TRIGGER b2_1 BEFORE INSERT ON b2 FOR EACH ROW WHEN   (SELECT COUNT(*) FROM b2) > 0 BEGIN INSERT INTO b3 VALUES ('before'); END;")
box.sql.execute("CREATE TRIGGER b2_2 AFTER INSERT ON b2 FOR EACH ROW WHEN (SELECT COUNT(*) FROM b2) > 0 BEGIN INSERT INTO b3 VALUES ('after'); END;")
box.sql.execute("INSERT INTO b2 VALUES (1,1);")
box.sql.execute("SELECT * FROM b3;")
box.sql.execute("SELECT * FROM b2;")

Result = the foreign-key check fails, there are two rows in table b3, and there is one row in table b2.
Actually there should be no rows in any tables, because the foreign-key
check failure should cause the INSERT to fail completely, but that is the
subject of a different issue. What matters here is: it seems that the
foreign-key check happens after the firing of the AFTER INSERT trigger.

Start by running the supplied box.sql.execute reproduction with the b1, b2, and b3 tables and the b2_1 and b2_2 triggers. Trace the SQL insert path to determine when the foreign-key check runs relative to the BEFORE and AFTER triggers. Done means the execution order matches the intended foreign-key behavior described in the issue.