Clarke has tried to downplay the significance of Albion losing three games in succession after climbing to third in the table last month.
But the former West Ham number two knows the significance of the Baggies recapturing the winning habit sooner rather than later.
Clarke said: "I don't think it is a massive test. The test for me as a number one came when I walked into this job in the summer.
"That was the big test. We started well this season and, if you took out the defeats we've had and spread them over a course of the season, everyone would be saying we are doing fantastic.
"That's the line I tend to stick with. If I had been offered the top six in mid-December, I would have been pleased with the points tally we've got.
"But it is up to us to make sure the bad run stops now and we start to pick up more points.
"The players this week have been positive, not dwelling on the three defeats. They are looking forward to the run of games coming up.
"It would have been nice if we could have kept the good run going a little longer, but we didn't, and we have to make sure the next run starts on Sunday.
"We know we've lost the last three because everyone keeps telling us, but we are not going to forget that anyway. We know we have to address it this weekend."
Clarke insists he enjoyed his time as number two to Gianfranco Zola with the Hammers despite the pair being sacked at the end of the 2009-10 season.
He is also a big admirer of West Ham boss Sam Allardyce and believes it is unfair to stereotype the style of football his teams have produced during his managerial career.
Clarke said: "It is a good club, I enjoyed my experience there and it's good to see them doing well in the Premier League.
"They have passionate fans who care about their team, they try to play football the right way.
"I don't care what anyone says about Sam and his teams, he always tries to play football the right way.
"They try to be positive, they try to get balls in the box, they try to score goals, and for me that is always the right way to play football."
Clarke added: "You can become stereotyped if you like and there is a little bit of that with Sam.
"He has got good football players in that team. I've watched a number of their games this season and they play good football when they are allowed to play good football.
"If it becomes a scrap then they are a team that can stand up for a scrap as well. Whatever type of game it is at the weekend, West Ham will be ready for it.
"But I can assure West Ham we will be ready for it as well."
Clarke admits he has a lengthy injury list to worry about ahead of Sunday's game including keeper Ben Foster (groin), midfielder Claudio Yacob (hamstring) and Liam Ridgewell (hamstring).
He said: "I've got a number of issues. There are a number of injury doubts for the game this weekend, more than you guys have got noted down.
"It is a test of the squad strength but it is something I don't shy away from because I've got a good squad and it will certainly be tested over the next four or five weeks."