import static org.assertj.core.api.Assertions.assertThat; import static org.assertj.core.api.Assertions.assertThatExceptionOfType; import org.junit.jupiter.api.Disabled; import org.junit.jupiter.api.DisplayName; import org.junit.jupiter.api.Test; public class CircularBufferTest { @Test @DisplayName("reading empty buffer should fail") public void readingFromEmptyBufferShouldThrowException() { CircularBuffer buffer = new CircularBuffer<>(1); assertThatExceptionOfType(BufferIOException.class) .isThrownBy(buffer::read) .withMessage("Tried to read from empty buffer"); } @Disabled("Remove to run test") @Test @DisplayName("can read an item just written") public void canReadItemJustWritten() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(1); buffer.write(1); assertThat(buffer.read()).isEqualTo(1); } @Disabled("Remove to run test") @Test @DisplayName("each item may only be read once") public void canReadItemOnlyOnce() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(1); buffer.write(1); assertThat(buffer.read()).isEqualTo(1); assertThatExceptionOfType(BufferIOException.class) .isThrownBy(buffer::read) .withMessage("Tried to read from empty buffer"); } @Disabled("Remove to run test") @Test @DisplayName("items are read in the order they are written") public void readsItemsInOrderWritten() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(2); buffer.write(1); buffer.write(2); assertThat(buffer.read()).isEqualTo(1); assertThat(buffer.read()).isEqualTo(2); } @Disabled("Remove to run test") @Test @DisplayName("full buffer can't be written to") public void fullBufferCantBeWrittenTo() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(1); buffer.write(1); assertThatExceptionOfType(BufferIOException.class) .isThrownBy(() -> buffer.write(2)) .withMessage("Tried to write to full buffer"); } @Disabled("Remove to run test") @Test @DisplayName("a read frees up capacity for another write") public void readFreesUpSpaceForWrite() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(1); buffer.write(1); assertThat(buffer.read()).isEqualTo(1); buffer.write(2); assertThat(buffer.read()).isEqualTo(2); } @Disabled("Remove to run test") @Test @DisplayName("read position is maintained even across multiple writes") public void maintainsReadPositionAcrossWrites() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(3); buffer.write(1); buffer.write(2); assertThat(buffer.read()).isEqualTo(1); buffer.write(3); assertThat(buffer.read()).isEqualTo(2); assertThat(buffer.read()).isEqualTo(3); } @Disabled("Remove to run test") @Test @DisplayName("items cleared out of buffer can't be read") public void cantReadClearedItems() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(1); buffer.write(1); buffer.clear(); assertThatExceptionOfType(BufferIOException.class) .isThrownBy(buffer::read) .withMessage("Tried to read from empty buffer"); } @Disabled("Remove to run test") @Test @DisplayName("clear frees up capacity for another write") public void clearFreesUpCapacity() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(1); buffer.write(1); buffer.clear(); buffer.write(2); assertThat(buffer.read()).isEqualTo(2); } @Disabled("Remove to run test") @Test @DisplayName("clear does nothing on empty buffer") public void clearDoesNothingOnEmptyBuffer() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(1); buffer.clear(); buffer.write(1); assertThat(buffer.read()).isEqualTo(1); } @Disabled("Remove to run test") @Test @DisplayName("overwrite acts like write on non-full buffer") public void overwriteActsLikeWriteOnNonFullBuffer() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(2); buffer.write(1); buffer.overwrite(2); assertThat(buffer.read()).isEqualTo(1); assertThat(buffer.read()).isEqualTo(2); } @Disabled("Remove to run test") @Test @DisplayName("overwrite replaces the oldest item on full buffer") public void overwriteRemovesOldestElementOnFullBuffer() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(2); buffer.write(1); buffer.write(2); buffer.overwrite(3); assertThat(buffer.read()).isEqualTo(2); assertThat(buffer.read()).isEqualTo(3); } @Disabled("Remove to run test") @Test @DisplayName("overwrite replaces the oldest item remaining in buffer following a read") public void overwriteDoesntRemoveAnAlreadyReadElement() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(3); buffer.write(1); buffer.write(2); buffer.write(3); assertThat(buffer.read()).isEqualTo(1); buffer.write(4); buffer.overwrite(5); assertThat(buffer.read()).isEqualTo(3); assertThat(buffer.read()).isEqualTo(4); assertThat(buffer.read()).isEqualTo(5); } @Disabled("Remove to run test") @Test @DisplayName("initial clear does not affect wrapping around") public void initialClearDoesNotAffectWrappingAround() throws BufferIOException { CircularBuffer buffer = new CircularBuffer<>(2); buffer.clear(); buffer.write(1); buffer.write(2); buffer.overwrite(3); buffer.overwrite(4); assertThat(buffer.read()).isEqualTo(3); assertThat(buffer.read()).isEqualTo(4); assertThatExceptionOfType(BufferIOException.class) .isThrownBy(buffer::read) .withMessage("Tried to read from empty buffer"); } }