What are the different types of test oracles?

There are many types of test oracles, but the following are the most common:
1. Explicit test oracles: These oracles compare the software application’s actual output to the expected output.
2. Implicit test oracles: These oracles do not compare the actual output to the expected output explicitly. Instead, they rely on the tester’s knowledge of the software application to determine whether the test case was passed or failed.