testRender: user input leaks through

[veracioux]

When I run tests in a terminal and then press some keys, they leak into the test. The tests were set up using plain await testRender(() => <App/>)

For example, I ran a few tests and kept holding the a key. This is what happened:

[kommander]

The testing setup currently isn't actually mocking process.stdin, the input mocks for key/mouse are writing to the actual process.stdin