The courts often use particular tests to decide whether particular legal requirements are satisfied or not. Most often, these tests are 'objective' rather than 'subjective'.
An objective test is one in which the court takes note of the relevant observable facts, and then draws a reasonable inference from those facts. For example, when deciding whether the parties to an agreement intended to be legally bound, the court takes account of all the circumstances in which the agreement was reached, and draws a reasonable inference from those facts as to whether it was intended to be legally binding.
Subjective tests, which are seldom applied, depend on the court determining what the person in question actually believed or intended.