Unit Testing in Ruby SWEN-250 Personal Software Engineering - PowerPoint PPT Presentation

Unit Testing in Ruby SWEN-250 Personal Software Engineering

Testing, 1 – 2 – 3 – 4, Testing…

What Does a Unit Test Test? • The term “unit” predates the O -O era. • Unit – “natural” abstraction unit of an O -O system: class or its instantiated form, object. • Unit Tests – verify a small chunk of code, typically a path through a method or function. • Not application level functionality.

Unit Testing Review • Test a cohesive functional entity: – Class – Stand alone function or functions • Verification testing – does the entity do what it's supposed to do. • Greatly facilitated by unit test frameworks. – JUnit for Java – NUnit for .NET – MiniTest::Test for Ruby

How Do We Unit Test? • Print Statements (diffs against benchmarks) • Debuggers – examine variables, observe execution paths. • Typically done by unit developer. • Best benefit if running of tests is automated . • Tests best run in isolation from one another. • Tests built incrementally as product code is developed.

The Typical Test Cycle • Develop a suite of test cases • Create some test fixtures to support the running of each test case. • Run the test – capture test results. • Clean-up fixtures, if necessary. • Report and analyze the test results.

Why is Unit Testing Good? • Identifies defects early in the development cycle. • Many small bugs ultimately leads to chaotic system behavior • Testing affects the design of your code. • Successful tests breed confidence. • Testing forces us to read our own code – spend more time reading than writing • Automated tests support maintainability and extendibility.

Why Don’t We Unit Test? • “Coding unit tests takes too much time” • “I’m to busy fixing bugs to write tests” • “Testing is boring – it stifles my creativity” • “My code is virtually flawless…” • “Testing is better done by the testing department” • “We’ll go back and write unit tests after we get the code working”

Basic xUnit Components • Create a test class that extends class Test • Create a testxxx() method for each individual test to be run. • Create a test fixture – resources needed to support the running of the test. • Write the test, collect interesting test behavior • Tear down the fixture (if needed) • Run the tests.

Key xUnit Concepts • assert - – assertEquals( expected, actual ) – also NotEquals – assertNull( actual result ) – also NotNull – assertTrue( actual result) - also False • failures – – Exceptions raised by asserts (expected) • errors – – Ruby runtime exceptions (not expected)

Unit Testing in Ruby • MiniTest::Test – All unit test classes inherit from this class – Example: class MyClass < MiniTest::Test – setup / teardown – test* methods run in random order • Assertions (change assert to refute for negative) – assert( boolea n, [ message ]) – assert_equal( exp , act , [ message ]) – assert_raises( Exception ) block – assert_nil( obj , [ message ]) – Full list in http://ruby-doc.org/stdlib-2.0.0/libdoc/minitest/rdoc/MiniTest/Assertions.html

Queue: (queue.rb) cl class ass Q Queu ueue # # Ex Excep epti tion on cl clas ass f for or t taki king ng va valu lues es fr from om an an e emp mpty y qu queue ue. cla class ss Em Empty pty < < Sta Standa ndardE rdError ror def def ini initia tializ lize supe uper(" r("Empt mpty y que queue" ue") end end end end # I # Ini nitia tializ lizatio tion def def init nitial ialize ze @co @conte ntents nts = = Arr Array. ay.new new sel self end end # Q # Que ueue ue is is empt mpty y if if its its siz size e is is zer zero def def empt mpty? y? siz size = e == 0 = 0 end end # Q # Que ueue ue siz size - nu numbe mber o r of el elem ement ents def def size ize @co conte ntents nts.siz size end end

Queue: (queue.rb) # A # Add dd a a val value t e to o the the ta tail o l of f the the qu queue ue def def t tail ail= v = value lue @co @conte ntents nts[@co @cont ntent ents.s s.size] ze] = = v valu alue val value ue end end # R # Ret eturn urn th the fi firs rst e t elem lement nt in in th the q e queue eue w with ithout out rem remov oving ing it it def def p peek eek rai raise se Emp Empty i y if f emp empty? ty? @c @cont nten ents ts[0] 0] end end # R # Ret eturn urn an and re remo move ve the the fir first st qu queue eue ele eleme ment nt def def h head ead val value ue = p = peek ek @co @conte ntents nts.del delet ete_a e_at(0 t(0) val value ue end end en end

TestQueue: (test_queue.rb) require ‘minitest/autorun' require_relative ‘queue' cl class ass T Test estQue Queue < e < M Mini iniTes Test::T ::Tes est def def s setu etup @tq @tq = = Que Queue.n e.new ew end end # Che # C heck ck pro proper er em empty pty qu queue ue be behav havior ior def def t test est_ne _new_qu _queu eue ass assert ert( @ ( @tq.s q.siz ize = e == 0 = 0, "N "New ew qu queue eue siz size e not not ze zero" o" ) ass assert ert( @ ( @tq.e q.emp mpty? ty?, " , "New ew qu queue eue no not em empt pty" y" ) as asser ert_ t_ra raise ses( s(Que ueue ue:: ::Emp mpty ty) { { @ @tq tq.pe peek ek } ass assert ert_ra _raises ses(Q (Queu ueue:: e::Empt mpty) y) { { @tq @tq.hea head d } end end

TestQueue: (test_queue.rb) # C # Che heck ck pro proper er FI FIFO FO beh behavio vior. r. Mu Must st end nd wi with th an an empt mpty y que queue. ue. def def test est_fi _fifo_c o_che heck ck tes test_v t_valu alues = % = %w{ w{ A B A B C } C } # # init init an a n arr rray ay of of thre hree e val values ues tes test_v t_valu alues.e s.eac ach { | { |v| v| @ @tq. tq.tai tail = = v } v } # # ad add t d to th the e que queue ue siz size = e = @ @tq tq.si .size ze # e # expe xpect ct 3 3 for for th the qu queu eue s e size ize tvl tvlen en = = te test_ st_va value lues.l s.lengt ngth ass assert ert( s ( size ze == == tvlen tvlen, "# "#{tvl tvlen} e } elem lement ent q queu ueue g e gives ves s size ize of of #{s #{siz ize}" e}" ) ) ref refute ute( @ ( @tq.e q.emp mpty ty?, ?, "N "Non on-em empty pty qu queue ue re repor ports ts empt mpty" y" ) ) #It #Itera erate te thro hroug ugh t h the he arra rray y and and re remove ove e each ach on one en entr try tes test_v t_valu alues.e s.eac ach do do |v |v| qv = v = ni nil #d #dec eclar lare v e varia riabl ble t e to p o pass ss be betwe tween en asse ssert rtion ions qv = v = @ @tq tq.pe .peek ek # n # no e o exce xcept ption ion if if cod code e is is cor correct ect ass sser ert_ t_equ qual al(v, v, q qv, v, '@ '@tq tq.pe peek ek:') :') qv qv = @ @tq tq.he .head ad asse ssert_ rt_equa qual(v, v, qv, qv, '@ '@tq. tq.hea head:') :') end end ass assert ert_ra _raises ses(Q (Queu ueue:: e::Empt mpty) y) { { @tq. tq.pee peek } # } #emp empty n y now ow as asser ert_ t_ra raise ses(Q (Que ueue ue:: ::Emp mpty ty) { { @ @tq tq.he head ad } end end en end