lessons from testing
DESCRIPTION
I have run hundreds of test-driven coding dojos using the cyber-dojo app. I see the same test anti-patterns time after time after time. Do some of your tests exhibit the same same anti-patterns?TRANSCRIPT
2
Avoid unnecessary burning of calories!
FizzBuzz
3
E09E8C snake 4
what do I notice?
5
6
Suppose we measure the average cyclomatic complexity of the code under test and the test
code.
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Higher number means more complex.
codetests
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3.7 2.1>
codetests
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3.7 2.1
teststests
4.3 >>
codetests
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3.7 2.1
teststests
4.3NO!>>
codetests
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2.1 2.1==
codetests
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2.1 2.1==NO!
codetests
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2.0 2.1<
codetests
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2.0 2.1<NO!
codetests
1.0 2.1
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<<<
codetests
1.0 2.1
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YES<<<
17E09E8C wolf
~> Simple1.0
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what do I notice most?
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Duplication!
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Duplication usually indicates
a missing abstraction
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what do I notice now?
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Duplication!
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what do I notice now?
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Duplication!
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what do I notice now?
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missing examples?
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what do I notice now?
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better test names?
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what do I notice now?
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different_identifier_style?differentIdentifierStyle?
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that's ok!
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what do I notice now?
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duplication?
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this is worse!
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how about this?
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1.0
Specific ?
21F1F3 alligator
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!21F1F3 alligator
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Specific ?
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Specific :-)
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Repetition ?
?
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Repetition can indicate a missing
abstraction
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Specific
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Specific
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Recently Used List
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e.g. Recent Files...
52DE3BF3 buffalo
what do I notice?
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Duplication!
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What's left?
WTF?redblue
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e.g. Files!
56BAC947 snake
better!
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better still
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What do I notice now?
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Duplication!
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What does assertEquals()
print when it fails?
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Do yourdiagnostics diagnose?
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What diagnostic
do you want?
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How about this?
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Make it so!
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A
B C
D E F
G
external external
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A
B C
tAmockist style
B' C'
D E F
G
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A
B C
D E F
G
mockist style
tB
E'D'
C'
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A
B C
D E F
G
mockist styleG'
F'
B'
tC
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code tests
mockist style
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A
B C
tA
D E F
G
classic style
D' F'
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classic style
code tests
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the.law.of.demeter
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which is more important?
the code or the tests?
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both
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You cannot determine the character or nature of a system within itself. Attempts to do so lead to confusion and disorder.
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code and testsco-evolve
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evolution is always co-evolution
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testing
time
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debugging
time
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debugging = removing what you don't want
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if you get rid of what you don't want, will you be left with what you do want?
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if you get rid of what you don't want, will you be left with what you do want??
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testing
time
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specification
time
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specific.........
time
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SummaryBurning calories - a metaphor for understandabilityTests should be simple, linear, low complexityTests should be specificLong_specific_test_names_is_ok Duplication usually means a missing abstractionRepetition can indicate a missing abstraction tooDo your diagnostics diagnose? custom assertions Don't cheat on test data - "String1" vs "red"Overuse Mockist style and you will regret itCode and tests co-evolveTest at the end is often debuggingTest at the beginning as specification
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code with no testsFB75B3
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Lesson ONE
test code must be much simpler than the code it
tests