Inline Tests

This gem defines a method of storing your tests as part of the method they're testing.

Syntax

To add inline tests to a method, simply prefix the method's def with tested and then add a tests block. Each assert can take an optional description to make your output a little nicer.

For example, say you have the following method:

def integer_division(x, y)
  return Float::INFINITY if y.zero?
  x.to_i / y.to_i
end

This is what that method could look like with inline tests:

tested def integer_division(x, y)
  return Float::INFINITY if y.zero?
  x.to_i / y.to_i
end,
tests do
  assert integer_division(6, 3) == 2, "divides correctly"
  assert integer_division(5, 3) == 1, "uses integer division"
  assert integer_division(0, 3) == 0, "0 / anything = 0"
  assert integer_division(3, 0) == Float::INFINITY
end

You can also flag methods that need tests but don't have them yet with the untested prefix. These methods are listed at the end of the test suite and made easily-greppable for anyone itchin' to write more tests.

untested def integer_division(x, y)
  return Float::INFINITY if y.zero?
  x.to_i / y.to_i
end

Fuzzy testing

This library also supports fuzzy testing. To use it, use the fuzz keyword with square brackets as if they were parentheses. Square brackets can also be used with non-range values. Every combination in every range will be tested; the condition must be true for every permutation in order for the test to pass.

For example,

tested def add x, y
  x + y
end,
tests do
  assert_greater_than fuzz[0, (1..1_000)], 0, 'adding anything to zero should be greater than zero'
  assert_equal        fuzz[0, 0],          0, '0 + 0 = 0'
end

tested def multiply x, y
  x * y
end,
tests do
  assert_greater_than fuzz[(-100..-1), (-100..-1)], 0, 'multiplying any two negatives should yield a positive'
end

Example output

In order to run the test suite, all you need to do is call InlineTests.run! from anywhere.

$ ruby 07_lib_usage.rb 
Starting inline test suite:
  main::add - PASSED (0.000000271 seconds)
  main::integer_division - PASSED (0.000000239 seconds)
  main::multiply - PASSED (0.000000292 seconds)
  main::divide - PASSED (0.000000196 seconds)
4 inline tests ran in 0.000049601 seconds.
  4 PASSED
  0 FAILS

Example from Ruby on Rails:

$ rails c
Running via Spring preloader in process 9112
Loading development environment (Rails 6.1.0)
irb(main):001:0> InlineTests.run!
Starting inline test suite:
  Analysis::Readability::AutomatedReadabilityIndexService::self.formula - FAILED (0.000279689 seconds)
    FAILED:
      test_type: assert_equal
      lhs: -8
      rhs: 5
1 inline tests ran in 0.000353155 seconds.
  0 PASSED
  1 FAILS

1 methods still need tests:
  Analysis::Readability::AutomatedReadabilityIndexService#baseline
    app/services/analysis/readability/automated_readability_index_service.rb:37