@Before
  public void setup() {
    MockitoAnnotations.initMocks(this);
    when(this.keyValueStoreMetrics.gets()).thenReturn(this.getsCounter);
    when(this.keyValueStoreMetrics.bytesRead()).thenReturn(this.bytesReadCounter);
    when(this.keyValueStoreMetrics.puts()).thenReturn(this.putsCounter);
    when(this.keyValueStoreMetrics.bytesWritten()).thenReturn(this.bytesWrittenCounter);
    when(this.keyValueStoreMetrics.deletes()).thenReturn(this.deletesCounter);
    this.inMemoryKeyValueStore = new InMemoryKeyValueStore(this.keyValueStoreMetrics);
  }
The length of the result of {@link #value(int)} will always be the same, so this can be used as the length for any
key produced by {@link #value(int)}.
samza-kv-inmemory/src/test/java/org/apache/samza/storage/kv/inmemory/TestInMemoryKeyValueStore.java