Stefan's little mocking library

This mocking library was built as a weekend project. It probably doesn't do everything you'd expect from your mocking library/framework, but it's relatively simple.

Usage

Let's see if we can test a piece of code that uses the following two interfaces (though they could just as well be classes):

interface Database {
    List<Integer> query() throws SQLException;
}

interface Service {
    int compute(int other);
    void doVoid();
}

Here's what a test could look like:

@Test
public void test() {
    // Create a database mock
    Mock<Database> databaseMock = Mock.createMock(Database.class);
    // Create a service mock
    Mock<Service> serviceMock = Mock.createMock(Service.class);

    // Expect the first call to Database to return {1, 2, 3}
    databaseMock.expect(Database::query).andReturn(List.of(1, 2, 3));
    // Expect the next (second) call to Database to throw an exception
    databaseMock.expect(Database::query).andThrow(SQLException::new);
    // Expect the Service.compute method to be called with an argument of value 666,
    // zero or more times, and return 0
    serviceMock.expect(srv -> srv.compute(666)).anyTimes().andReturn(0);
    // Expect the Service.compute method to be called twice with an argument value of 3,
    // and return 9 both times
    serviceMock.expect(srv -> srv.compute(3)).times(2).andAnswer(() -> 9);
    // Expect the Service.compute method to be called with an argument of value 42,
    // zero or more times, and return 42
    serviceMock.expect(srv -> srv.compute(42)).anyTimes().andReturn(42);
    // Expect the Service.doVoid method to be called
    serviceMock.expectVoid(Service::doVoid);

    // Verify the database mock. "db" will be passed in, which is the database mock
    databaseMock.verify(db ->
        // Verify the service mock. "srv" will be passed in, which is the service mock
            serviceMock.verify(srv ->
                assertThat(new MockTest().doSomething(db, srv), is(equalTo(81)))));
}

For completeness' sake, here's the definition of the doSomething function:

/**
 * Test code that exercices the mocks.
 */
private int doSomething(Database db, Service srv) throws SQLException {
    System.out.println("Compute 666: " + srv.compute(666));
    System.out.println("Compute 666: " + srv.compute(666));
    System.out.println("Query result: " + db.query());
    try {
        db.query();
    } catch (SQLException e) {
        System.err.println("Succesfully caught exception " + e);
    }
    int firstComputeResult = srv.compute(3);
    int result = firstComputeResult * srv.compute(3);
    srv.doVoid();
    return result;
}