Mock memory cache can be set up like screenshot below.

var firstTime = true;
object? expectedValue = "value from mock";
mockMemoryCache.Setup(x => x.TryGetValue(It.IsAny<object>(), out expectedValue))
          .Returns(() =>
          {
              if (firstTime)
              {
                  firstTime = false;
                  return false;
              }
              return true;
          });

mockMemoryCache
.Setup(x => x.CreateEntry(It.IsAny<object>()))
.Returns(Mock.Of<ICacheEntry>);

Reference: https://stackoverflow.com/a/11308543/8778795 https://github.com/devlooped/moq/issues/436

enter image description here