public void GetOrAddCorrelationId() { // Arrange var data = new HeaderDictionary { new KeyValuePair <string, StringValues>( "x-correlation-id", new StringValues(Guid.NewGuid().ToString())), }; // Act var actual = data.GetOrAddCorrelationId(); // Assert Assert.NotNull(actual); Assert.True(Guid.TryParse(actual, out _)); }