Add end-to-end tests

Author: viirya

datafusion/sqllogictest/test_files/scalar.slt

@@ -1878,3 +1878,51 @@ query T
 SELECT CONCAT('Hello', 'World')
 ----
 HelloWorld
+
+statement ok
+CREATE TABLE simple_string(
+  letter STRING,
+  letter2 STRING
+) as VALUES
+  ('A', 'APACHE'),
+  ('B', 'APACHE'),
+  ('C', 'APACHE'),
+  ('D', 'APACHE')
+;
+
+query TT
+EXPLAIN SELECT letter, letter = LEFT('APACHE', 1) FROM simple_string;
+----
+logical_plan
+Projection: simple_string.letter, simple_string.letter = Utf8("A") AS simple_string.letter = left(Utf8("APACHE"),Int64(1))
+--TableScan: simple_string projection=[letter]
+physical_plan
+ProjectionExec: expr=[letter@0 as letter, letter@0 = A as simple_string.letter = left(Utf8("APACHE"),Int64(1))]
+--MemoryExec: partitions=1, partition_sizes=[1]
+
+query TB
+SELECT letter, letter = LEFT('APACHE', 1) FROM simple_string;
+ ----
+----
+A true
+B false
+C false
+D false
+
+query TT
+EXPLAIN SELECT letter, letter = LEFT(letter2, 1) FROM simple_string;
+----
+logical_plan
+Projection: simple_string.letter, simple_string.letter = left(simple_string.letter2, Int64(1))
+--TableScan: simple_string projection=[letter, letter2]
+physical_plan
+ProjectionExec: expr=[letter@0 as letter, letter@0 = left(letter2@1, 1) as simple_string.letter = left(simple_string.letter2,Int64(1))]
+--MemoryExec: partitions=1, partition_sizes=[1]
+
+query TB
+SELECT letter, letter = LEFT(letter2, 1) FROM simple_string;
+----
+A true
+B false
+C false
+D false