Added/Updated tests\functional\sqlancer\tidb_challenge_19_test.py: adapted from article provided in SQLancer documentation.

Author: pavel-zotov

tests/functional/sqlancer/tidb_challenge_19_test.py

@@ -0,0 +1,31 @@
+#coding:utf-8
+
+"""
+ID:          n/a
+ISSUE:       https://github.com/tidb-challenge-program/bug-hunting-issue/issues/19
+TITLE:       Incorrect result for LEFT JOIN and CASE operator
+DESCRIPTION:
+    https://github.com/sqlancer/sqlancer/blob/main/CONTRIBUTING.md#unfixed-bugs
+    https://github.com/sqlancer/sqlancer/blob/4c20a94b3ad2c037e1a66c0b637184f8c20faa7e/src/sqlancer/tidb/TiDBBugs.java
+"""
+
+import pytest
+from firebird.qa import *
+
+db = db_factory()
+
+test_script = """
+    set list on;
+    CREATE TABLE t0(c0 INT);
+    CREATE TABLE t1(c0 INT);
+    INSERT INTO t0 VALUES (0);
+    INSERT INTO t1 VALUES (0);
+    SELECT * FROM t1 LEFT JOIN t0 ON t0.c0 = t1.c0 WHERE (CASE t0.c0 WHEN 0 THEN t1.c0 ELSE 1 END) <> 0; -- expected: {}, actual: {0|NULL}
+"""
+
+act = isql_act('db', test_script)
+
+@pytest.mark.version('>=3.0')
+def test_1(act: Action):
+    act.execute(combine_output = True)
+    assert act.clean_stdout == ''