I would also avoid using because it's a magic number. I would use: 
```ruby
context "#push" do
 let(:element) { 1 }
 it "pushes an element into the stack" do
  stack.push(element)
```

```ruby
# use
expect(stack).to_not be_empty
# instead of
expect(stack.empty?).to eq false
```
Also, that's not enough testing. We need to make sure it pushes the element that was passed in, not "any" element. So:
```ruby
expect(stack).to eq [element] #this checks for length and content
```