title: How accurate is a Jest coverage test report? How is Jest test coverage calculated? How should I analyze the coverage findings?
body: <p>I am working on updating tests for an Express microservice. For some directories (i.e. our <code>/utils</code> folder), I have written plenty of tests, which show 80-90% coverage. In the <code>/routes</code> directory, there are 0 tests, but it shows 100%. </p>
  
  <p>Overall, I have this from our test coverage report:</p>
  
  <p><code>---------|----------|----------|----------|----------|----------------|
  File      |  % Stmts | % Branch |  % Funcs |  % Lines |Uncovered Lines |
  ----------|----------|----------|----------|----------|----------------|
  All files |    58.35 |    42.25 |    37.93 |    61.51 |
  .
  src/routes|      100 |      100 |      100 |      100 |                |
  .
  src/utils |    91.62 |    69.74 |     87.5 |    91.52 |                |
  </code></p>
  
  <p>I would analyze this as approximately 60% test coverage, but there wasn't much documentation on coverage.</p>