Feature: Fill up the buffer
Scenario: Buffer is empty
Given the buffer is empty
When the user fills up the buffer
Then the buffer should be full
Scenario: Buffer is partially filled
Given the buffer is partially filled
When the user fills up the buffer
Then the buffer should be full
Scenario: Buffer is already full
Given the buffer is full
When the user tries to fill up the buffer
Then the buffer should remain full and display an error message