added sample tests

Author: dmalan

README.md

@@ -43,3 +43,50 @@ s = cs50.get_string();
 1. Run `service postgresql start`.
 1. Run `psql -c 'create database test;' -U postgres.
 1. Run `touch test.db`.
+
+### Sample Tests
+
+```
+import cs50
+db = cs50.SQL("sqlite:///foo.db")
+db.execute("CREATE TABLE IF NOT EXISTS cs50 (id INTEGER PRIMARY KEY, val TEXT, bin BLOB)")
+db.execute("INSERT INTO cs50 (val) VALUES('a')")
+db.execute("INSERT INTO cs50 (val) VALUES('b')")
+db.execute("BEGIN")
+db.execute("INSERT INTO cs50 (val) VALUES('c')")
+db.execute("INSERT INTO cs50 (val) VALUES('x')")
+db.execute("INSERT INTO cs50 (val) VALUES('y')")
+db.execute("ROLLBACK")
+db.execute("INSERT INTO cs50 (val) VALUES('z')")
+db.execute("COMMIT")
+
+---
+
+import cs50
+db = cs50.SQL("mysql://root@localhost/test")
+db.execute("CREATE TABLE IF NOT EXISTS cs50 (id INTEGER PRIMARY KEY, val TEXT, bin BLOB)")
+db.execute("INSERT INTO cs50 (val) VALUES('a')")
+db.execute("INSERT INTO cs50 (val) VALUES('b')")
+db.execute("BEGIN")
+db.execute("INSERT INTO cs50 (val) VALUES('c')")
+db.execute("INSERT INTO cs50 (val) VALUES('x')")
+db.execute("INSERT INTO cs50 (val) VALUES('y')")
+db.execute("ROLLBACK")
+db.execute("INSERT INTO cs50 (val) VALUES('z')")
+db.execute("COMMIT")
+
+---
+
+import cs50
+db = cs50.SQL("postgresql://postgres@localhost/test")
+db.execute("CREATE TABLE IF NOT EXISTS cs50 (id INTEGER PRIMARY KEY, val TEXT, bin BLOB)")
+db.execute("INSERT INTO cs50 (val) VALUES('a')")
+db.execute("INSERT INTO cs50 (val) VALUES('b')")
+db.execute("BEGIN")
+db.execute("INSERT INTO cs50 (val) VALUES('c')")
+db.execute("INSERT INTO cs50 (val) VALUES('x')")
+db.execute("INSERT INTO cs50 (val) VALUES('y')")
+db.execute("ROLLBACK")
+db.execute("INSERT INTO cs50 (val) VALUES('z')")
+db.execute("COMMIT")
+```