Codecov always shows 100% incorrectly

Codecov incorrectly shows 100% coverage#

You know what's worse than no test coverage? A lie that it's 100% covered!

When you run nyc mocha test, you get this:

----------|----------|----------|----------|----------|-------------------|
File      |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files |       75 |       75 |      100 |       75 |                   |
 index.js |       75 |       75 |      100 |       75 |              6,14 |
----------|----------|----------|----------|----------|-------------------|

A report of 75% test coverage.

However, uploading the report to Codecov reports 100% test coverage - a blatantly wrong report!

Why is this happening?

Do you have code which has a condition and statement on the same line? Something like this?

if (!input) throw new Error('Missing arguments');
return input + input;

Some test coverage reporters cannot see statements on the same line as a condition and will generate a wrong report, therefore use curly brackets with conditions. Besides, this approach results in neater difference comparision in version control tools like Git.

Change the code above to:

if (!input) {
  throw new Error('Missing arguments');
}
return input + input;

The generated report will now be accurate and Codecov will show the correct 75% test coverage.

Summary#

Don't put statements on the same line as a condition. Put the statement within the curly brackets of the condition.