Apparently, you can't locate the Pregnancy Test filter on the TikTok app, according to HitC, because it's actually on Instagram. So, if you want to film a video with it, you'll have to film it via Instagram Stories, save it to your camera roll, and upload it to TikTok. 

First, open Instagram and click 'Your Story.' After browsing through all the filters, you'll see a magnifying glass at the end. Click it, and tap the other magnifying glass in the top right corner to search filters manually.

Then, you'll search ‘pregnancy test,' and select the 'Pregnancy Test' option by either intergalacticpimp or by petarxiv (they're basically the same). After filming your video, you can save it and upload to TikTok, and voila! You have your pregnancy test video. 

Yes, it's that easy, and we suppose it's worth it, if you want a filter "deciding" your destiny, that is.