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busted-flaky

busted-flaky is a busted extension for handling flaky specs, heavily inspired on RSpec::Retry. Using busted-flaky any block can be retried a specified number of times until it succeeds.

What is test flakiness?

A flaky test is a test that both passes and fails periodically without any code changes. Flaky tests are definitely annoying but they can also be quite costly since they often require engineers to retrigger entire builds on CI and often waste a lot of time waiting for new builds to complete successfully.

--- Test Flakiness – Methods for identifying and dealing with flaky tests

Installation

$ luarocks install busted-flaky

Usage

busted-flaky adds a new block called flaky. Use it around it and describe blocks for these to be retried an specific number of times until they succeed. All setup / teardown / finally blocks enclosed will also get executed.

describe("some thing", function()

  it("does stuff", function()

  end)

  flaky(function()

    it("does sometimes fail stuff", function()

    end)
  end)

  flaky("accepts a description too", function()

    describe("has a feature", function()
      lazy_setup(function()

      end)

      teardown(function()

      end)

      it("does stuff", function()

      end)
    end)
  end)
end)

A name level shortcut is available to wrap blocks on runtime, by tagging them with #flaky.

describe("some thing", function()

  it("does stuff", function()

  end)

  it("does sometimes fail stuff #flaky", function()

  end)

  describe("has a #flaky feature", function()

    lazy_setup(function()

    end)

    teardown(function()

    end)

    it("does stuff", function()

    end)
  end)
end)

The extension needs to be loaded by busted on runtime using the --helper argument for the runner.

$ busted -o gtest --helper=flaky path/to/some_spec.lua

Configuration

attempts

default: 5

Set the number of attempts the block will be retried until it succeeds.

format

default [#{tag} ({attempt}/{attempts}) {name}] like: [#flaky (3/5) some comment]

Format string for flaky attempts.

wait

default 0

Number of seconds to wait between flaky attempts.

callback

A callback that will be run between attempts. Can only configured through block attributes.

flaky("some flaky block", function()
  it(...)
end, {
  callback = function(element, status, attempts, ctx)
    -- gets run on every attempt
  end,
})

tag

default: flaky

The tag used for name level wrapping shortcut. Can only be configured through cli arguments.

cli arguments

  --attempts=NUM    number of attempts for flaky blocks (default: 5)
  --tag=TAG         tag for marking flaky blocks (default: 'flaky')
  --format=FORMAT   format string for flaky blocks
  --wait=TIME       seconds to wait between retries (default: 0)

$ busted --helper=flaky -Xhelper --attempts=10 -Xhelper --tag=failure ...

block attributes

flaky blocks accept block level attributes to customize them.

describe("something", function()
  it("does stuff", function() end)

  flaky(function()
    -- something
  end, {
    -- block level attributes
    wait = 5,
    retry = 10,
    callback = function(element, status, attempts, ctx)
      -- ...
    end
  })

Example

-- spec/flaky_spec.lua

local NOOP = function() end

describe("busted-flaky:", function()

  describe("when unused", function()
    describe("does leave describe blocks alone", function()
      it("and it blocks too", NOOP)
    end)
  end)

  describe("flaky block", function()

    describe("description", function()

      flaky("some description of the issue", function()
        it("can use an (optional) description", NOOP)
      end)

      flaky(function()
        it("does work without a description too", NOOP)
      end)

      flaky(function()
        it("does accept a different description format", NOOP)
      end, { fmt = "[ #flaky run {attempt} of {attempts} ]" })
    end)

    describe("contained blocks get retried until they succeed", function()

      local n = 1
      local p = 1

      after_each(function()
        p = p * 2
      end)

      flaky("only works the 3rd time", function()
        describe("assert", function()

          after_each(function()
            n = n + 1
          end)

          it(tostring(n) .. " == 3", function()
            assert.is_equal(3, n)
          end)
        end)
      end)

      describe("more attempts can be specified", function()
        flaky("only works the 7th time", function()
          it(tostring(p) .. " == 512", function()
            assert.is_equal(512, p)
          end)
        end, { attempts = 10 })
      end)

    end)

    describe("a tag shortcut can be used too", function()

      local n = 1
      local p = 1

      after_each(function()
        p = p * 2
      end)

      describe("#flaky assert", function()

        after_each(function()
          n = n + 1
        end)

        it(tostring(n) .. " == 3", function()
          assert.is_equal(3, n)
        end)
      end)

    end)

  end)

end)
$ busted -o gtest --helper=flaky spec/flaky_spec.lua
[==========] Running tests from scanned files.
[----------] Global test environment setup.
[----------] Running tests from example_spec.lua
[ RUN      ] example_spec.lua @ 7: busted-flaky: when unused does leave describe blocks alone and it blocks too
[       OK ] example_spec.lua @ 7: busted-flaky: when unused does leave describe blocks alone and it blocks too (0.58 ms)
[ RUN      ] example_spec.lua @ 16: busted-flaky: flaky block description [#flaky (1/5) some description of the issue] can use an (optional) description
[       OK ] example_spec.lua @ 16: busted-flaky: flaky block description [#flaky (1/5) some description of the issue] can use an (optional) description (0.50 ms)
[ RUN      ] example_spec.lua @ 20: busted-flaky: flaky block description [#flaky (1/5)] does work without a description too
[       OK ] example_spec.lua @ 20: busted-flaky: flaky block description [#flaky (1/5)] does work without a description too (0.54 ms)
[ RUN      ] example_spec.lua @ 24: busted-flaky: flaky block description [ #flaky run 1 of 5 ] does accept a different description format
[       OK ] example_spec.lua @ 24: busted-flaky: flaky block description [ #flaky run 1 of 5 ] does accept a different description format (0.54 ms)
[ RUN      ] example_spec.lua @ 44: busted-flaky: flaky block contained blocks get retried until they succeed [#flaky (1/5) only works the 3rd time] assert 1 == 3
example_spec.lua:45: Expected objects to be equal.
Passed in:
(number) 1
Expected:
(number) 3
[ RUN      ] example_spec.lua @ 44: busted-flaky: flaky block contained blocks get retried until they succeed [#flaky (2/5) only works the 3rd time] assert 2 == 3
example_spec.lua:45: Expected objects to be equal.
Passed in:
(number) 2
Expected:
(number) 3
[ RUN      ] example_spec.lua @ 44: busted-flaky: flaky block contained blocks get retried until they succeed [#flaky (3/5) only works the 3rd time] assert 3 == 3
[       OK ] example_spec.lua @ 44: busted-flaky: flaky block contained blocks get retried until they succeed [#flaky (3/5) only works the 3rd time] assert 3 == 3 (0.62 ms)
[ RUN      ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (1/10) only works the 7th time] 8 == 512
example_spec.lua:53: Expected objects to be equal.
Passed in:
(number) 8
Expected:
(number) 512
[ RUN      ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (2/10) only works the 7th time] 16 == 512
example_spec.lua:53: Expected objects to be equal.
Passed in:
(number) 16
Expected:
(number) 512
[ RUN      ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (3/10) only works the 7th time] 32 == 512
example_spec.lua:53: Expected objects to be equal.
Passed in:
(number) 32
Expected:
(number) 512
[ RUN      ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (4/10) only works the 7th time] 64 == 512
example_spec.lua:53: Expected objects to be equal.
Passed in:
(number) 64
Expected:
(number) 512
[ RUN      ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (5/10) only works the 7th time] 128 == 512
example_spec.lua:53: Expected objects to be equal.
Passed in:
(number) 128
Expected:
(number) 512
[ RUN      ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (6/10) only works the 7th time] 256 == 512
example_spec.lua:53: Expected objects to be equal.
Passed in:
(number) 256
Expected:
(number) 512
[ RUN      ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (7/10) only works the 7th time] 512 == 512
[       OK ] example_spec.lua @ 52: busted-flaky: flaky block contained blocks get retried until they succeed more attempts can be specified [#flaky (7/10) only works the 7th time] 512 == 512 (0.79 ms)
[ RUN      ] example_spec.lua @ 75: busted-flaky: flaky block a tag shortcut can be used too [#flaky (1/5) flaky]  assert 1 == 3
example_spec.lua:76: Expected objects to be equal.
Passed in:
(number) 1
Expected:
(number) 3
[ RUN      ] example_spec.lua @ 75: busted-flaky: flaky block a tag shortcut can be used too [#flaky (2/5) flaky]  assert 2 == 3
example_spec.lua:76: Expected objects to be equal.
Passed in:
(number) 2
Expected:
(number) 3
[ RUN      ] example_spec.lua @ 75: busted-flaky: flaky block a tag shortcut can be used too [#flaky (3/5) flaky]  assert 3 == 3
[       OK ] example_spec.lua @ 75: busted-flaky: flaky block a tag shortcut can be used too [#flaky (3/5) flaky]  assert 3 == 3 (0.61 ms)
[----------] 7 tests from example_spec.lua (27.96 ms total)

[----------] Global test environment teardown.
[==========] 7 tests from 1 test file ran. (29.37 ms total)
[  PASSED  ] 7 tests.

Credits

  • rspec:retry
  • busted