When I became a lead, one of the first real changes I noticed was the necessity of trusting those who worked for me.  When you are no longer doing all of the work directly, you have to report what others tell you.  This is very different from reporting on work you’ve done yourself.  This can feel really strange and can lead to a desire to double check everything.  Resist that temptation.
When you are an individual contributor, you *know* the truth of everything you say.  If someone asks you whether a feature works or not, you know the answer.  You are the one who ran the tests.  You have first-hand knowledge of its state.  Similarly, if someone asks you how far along programming for the new widget is, you know.  You are the one doing the programming.  

This all changes when you become a lead.  If your manager asks you the state of a feature, you can only repeat what you were told.  If the person telling you didn’t do things right, you’ll be passing on false information.  This takes some time to come to grips with.  It is a strange thing the first time you have to do this.  Up until now, you’ve always known for certain the truth of your statements.  Now, you do not and really cannot know.

How then should a new lead deal with this?  You have to just trust people.  Until they prove that they are not trustworthy, you need to just believe them.  If they tell you that FeatureX is working, you have to report that.  You don’t have the time to check up on everything, nor should you if you did.  You have someone reporting to you whose job it is to do this work.  You must assume competence.  If you do not, you’ll harm your relationship with that employee and you’ll run yourself ragged.  Whoever hired these people verified that they were competent.  Unless something changed, they still are.  Feel free to spend some time with your employees trying to understand what they are doing and how they are approaching the problems.  Do this to educate yourself, not to question their work.  With time, you will learn the abilities of those reporting to you and become much more comfortable with their reports.