Give detail discussion about Black box testing.

• Black box or behavioural testing emphasis on the functional needs of the software.
• It is used during the last stage of testing.
• Syntax driven testing is preferable for the specification that described by a certain grammar.
• Decision table based testing is applied when the original software requirement have been evaluated in the form of " if-then" statements.
• Liquid level control is the scope of a simple control problem which is considered to check the liquid level. It has two sensors.
• Cause effect graphs in functional testing.