add test for empty string

Author: codehz

tests/test_emptystr.nim

@@ -0,0 +1,8 @@
+import easy_sqlite3
+import std/[unittest, tables]
+
+proc getEmptyString(): tuple[value: string] {.importdb: "SELECT ''".}
+
+test "get empty string":
+  var db = initDatabase(":memory:")
+  check db.getEmptyString() == (value: "")