Perform magic checks on a database file for better error messaging.

tests/database/t_can_create_in_memory.nim

@@ -4,4 +4,5 @@ import kuzu
 
 var db = newKuzuDatabase()
 assert db.path == "(in-memory)"
+assert db.kind == memory
 

tests/database/t_checks_for_valid_kuzu_file.nim

@@ -0,0 +1,23 @@
+# vim: set et sta sw=4 ts=4 :
+
+import
+  std/files,
+  std/paths,
+  std/re
+
+import kuzu
+
+const NOT_A_DATABASE_PATH = Path( "tmp/not-a-db" )
+
+NOT_A_DATABASE_PATH.removeFile()
+var fh = NOT_A_DATABASE_PATH.string.open( fmWrite )
+fh.write( "Hi." )
+fh.close
+
+try:
+    discard newKuzuDatabase( $NOT_A_DATABASE_PATH )
+except KuzuException as err:
+    assert err.msg.contains( re"""Unable to open database: "tmp/not-a-db" Doesn't appear to be a Kuzu file""" )
+
+NOT_A_DATABASE_PATH.removeFile()
+

tests/database/t_creates_with_default_config.nim

@@ -12,6 +12,7 @@ DATABASE_PATH.removeFile()
 var db = newKuzuDatabase( $DATABASE_PATH )
 
 assert db.path == $DATABASE_PATH
+assert db.kind == disk
 assert db.config == kuzuConfig()
 assert db.config.read_only == false