5 Questions Every Unit Test Must Answer

How to Write Better Tests

Eric Elliott
Aug 29, 2015 · 7 min read

Most Developers
Don’t Know How to Test

Why Bother with Test Discipline?

The Science of TDD

Write Tests First

Before you implement,
write the test.

What’s in a Good Unit Test?

The Unit Test as a Bug Report

A failing test should read
like a high-quality bug report.

What’s in a good test failure bug report?

Image for post
Image for post
Example of a good failure report.

Start by answering “what are you testing?”:

What should the feature do?

'compose() should return a function.'

What component aspect are we testing?

test('<What component aspect are we testing?>', assert => {
});
test('Compose function output type.', assert => {
});
test('Compose function output type.', assert => {
'compose() should return a function.'
});

What is the Output (Expected and Actual)?

Equal is your new default assertion.
It is the staple of every good test suite.

A Challenge

  const actual = '<what is the actual output?>';
const expected = '<what is the expected output?>';
  const actual = '<how is the test reproduced?>';
  const actual = typeof compose();
const expected = 'function';
  assert.equal(actual, expected,
'compose() should return a function.');

A Unit Test Template:

Next Steps

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