Blogger - FPOWJPWB - RetryTest

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.ExpectedException;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;

public class RetryTest {
    private static final String RESULT = "operation result";

    class State {
        public boolean operationCalled = false, preRetryCalled = false;
        public int operationCalledTimes = 0, preRetryCalledTimes = 0;
    }

    @Rule
    public ExpectedException thrown = ExpectedException.none();

    @Test
    public void noRetriesNeeded() throws Exception {
        String result = Retry.retry(
                // 1 retry
                1,
                // operation
                new Function0<String>() {
                    public String apply() {
                        return RESULT;
                    }
                },
                // checker
                new Function1<String, Boolean>() {
                    public Boolean apply(String checkedResult) {
                        return true;
                    }
                },
                // pre-retry
                new Function0<Void>() {
                    public Void apply() {
                        fail("wrong pre-retry");
                        return null;
                    }
                },
                // use default error message
                null
        );

        assertEquals(RESULT, result);
    }

    @Test
    public void succeededAfterRetry() throws Exception {
        final State state = new State();
        String result = Retry.retry(
                // 1 retry max
                1,
                // operation
                new Function0<String>() {
                    public String apply() {
                        return RESULT;
                    }
                },
                // checker
                new Function1<String, Boolean>() {
                    public Boolean apply(String checkedResult) {
                        final boolean result;
                        state.operationCalledTimes++;
                        if (state.operationCalled) {
                            result = true;
                        } else {
                            state.operationCalled = true;
                            result = false;
                        }
                        return result;
                    }
                },
                // pre-retry
                new Function0<Void>() {
                    public Void apply() {
                        state.preRetryCalledTimes++;
                        if (state.preRetryCalled) {
                            fail("pre-retry already called");
                        } else {
                            state.preRetryCalled = true;
                        }
                        return null;
                    }
                },
                // use default error message
                null
        );

        assertEquals(RESULT, result);
        assertTrue(state.operationCalled);
        assertTrue(state.preRetryCalled);
        assertEquals(2, state.operationCalledTimes);
        assertEquals(1, state.preRetryCalledTimes);
    }

    @Test
    public void failedAfterRetriesExhausted() throws Exception {
        final String errorMessage = "oops";
        thrown.expect(Exception.class);
        thrown.expectMessage(errorMessage);

        final State state = new State();
        Retry.retry(
                // 5 retries
                5,
                // operation
                new Function0<String>() {
                    public String apply() {
                        return RESULT;
                    }
                },
                // checker
                new Function1<String, Boolean>() {
                    public Boolean apply(String checkedResult) {
                        return false;
                    }
                },
                // pre-retry
                new Function0<Void>() {
                    public Void apply() {
                        state.preRetryCalledTimes++;
                        assertFalse(state.preRetryCalledTimes > 5);
                        return null;
                    }
                },
                // custom error message
                errorMessage
        );
    }
}