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The non-unitary in TDD TDD in presence of dependencies Johan Martinsson @johan_alps

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The problem(s)

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We don’t know how to test

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We don’t know what to test

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It's hard to mock

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UNIT test don’t make sense

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Surprises in integration • Rights not con fi gured • Heteregenous format, ex a date fi eld can have ddmm or dd/mm/yyyy • Apis lying about the information • Text recognition cuts things strangely • Performance in splitting a pdf • Rate limitation • Sending emails, is it well formed? Xavi cabrera Unsplash

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Solutions!

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No tests

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Buy the tests

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High level tests

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Just write them!

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Test last • When do they serve? • Who do they serve? • How do know if they’re good? Simon Berger Unsplash

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My suggestion Start as early as possible

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Example mapping

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Start TDD with High level, integrated tests

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How do we TDD this? What are the boundaries of the tests?

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Result: Mockist style

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Result: Classical style

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In what order?

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Inside Out

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Outside In

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Outside-In Classical TDD

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Types of tests and qualities

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The story of a story Find the position of a name in a pdf and if it is found, save it to the db. • Create a new lambda • Con fi gure lambda rights • Validate user rights • Extract data from request • Call external service • Parse result • If found, load existing data in db • Save data to db Etienne Girardet Unsplash

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Example work fl ow • Write test agains deployed version • Validate function exists • Validate function does not fail • … • Write integrated test against version in IDE • Save hard-coded value to db • Deployed test validates function rights • Write another test • Call external service & parse result • More tests to vary input & expectations • Discover false assumptions • Isolate & refactor tests

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Now Isolate

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Architecture hexagonale

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Dependency Adapter

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Examples of adapters • Repository • Ex PersonRepository • File read/write wrapper • Message queue • External service wrapper • Ex Pdf extractor, email service …

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Applicatio n test

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Adapter Adapte r test

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func TestExtractData(t *testing.T) { t.Skip("this costs 5 cts for each call, only activate when working on the adapter" ) client, err := newAdobeClient(t ) file, result, err := extract(t, "./Feuille_de_Presence_demembrement.pdf", client ) defer file.Close( ) assert.Nil(t, err ) assert.Len(t, result.Pages, 3 ) } Example expensive test

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Example not isolating, yet // todo make this test faster (mocking ghostscript? ) func Test3Pages(t *testing.T) { testDir := findTestDir( ) service := createServiceWithFakeClient("analysis-result-2050-sd.json", testDir ) err, result := extractText(t, "2050-sd.pdf", testDir, service ) require.Nil(t, err ) require.NotEmpty(t, result ) }

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Example switching back and forth //textractClient := realTextractClient( ) textractClient := plaquette.FakeTextractFromJson(baseDir + “analysis-result-2033.json" ) // … the rest of the tes t

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Run the adapter tests for the simulators Real adapter Simulator Depend 
 ency Interface Test Flag for activation

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Integrated tests in a CI?

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Conclusion • Delay isolation • Delay low level tests • In a story • In a product • Separate integrated tests