1 | =head1 NAME
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2 |
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3 | Test::Tutorial - A tutorial about writing really basic tests
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4 |
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5 | =head1 DESCRIPTION
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6 |
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7 |
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8 | I<AHHHHHHH!!!! NOT TESTING! Anything but testing!
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9 | Beat me, whip me, send me to Detroit, but don't make
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10 | me write tests!>
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11 |
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12 | I<*sob*>
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13 |
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14 | I<Besides, I don't know how to write the damned things.>
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15 |
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16 |
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17 | Is this you? Is writing tests right up there with writing
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18 | documentation and having your fingernails pulled out? Did you open up
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19 | a test and read
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20 |
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21 | ######## We start with some black magic
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22 |
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23 | and decide that's quite enough for you?
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24 |
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25 | It's ok. That's all gone now. We've done all the black magic for
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26 | you. And here are the tricks...
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27 |
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28 |
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29 | =head2 Nuts and bolts of testing.
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30 |
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31 | Here's the most basic test program.
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32 |
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33 | #!/usr/bin/perl -w
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34 |
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35 | print "1..1\n";
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36 |
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37 | print 1 + 1 == 2 ? "ok 1\n" : "not ok 1\n";
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38 |
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39 | since 1 + 1 is 2, it prints:
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40 |
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41 | 1..1
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42 | ok 1
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43 |
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44 | What this says is: C<1..1> "I'm going to run one test." [1] C<ok 1>
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45 | "The first test passed". And that's about all magic there is to
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46 | testing. Your basic unit of testing is the I<ok>. For each thing you
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47 | test, an C<ok> is printed. Simple. B<Test::Harness> interprets your test
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48 | results to determine if you succeeded or failed (more on that later).
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49 |
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50 | Writing all these print statements rapidly gets tedious. Fortunately,
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51 | there's B<Test::Simple>. It has one function, C<ok()>.
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52 |
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53 | #!/usr/bin/perl -w
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54 |
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55 | use Test::Simple tests => 1;
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56 |
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57 | ok( 1 + 1 == 2 );
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58 |
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59 | and that does the same thing as the code above. C<ok()> is the backbone
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60 | of Perl testing, and we'll be using it instead of roll-your-own from
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61 | here on. If C<ok()> gets a true value, the test passes. False, it
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62 | fails.
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63 |
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64 | #!/usr/bin/perl -w
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65 |
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66 | use Test::Simple tests => 2;
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67 | ok( 1 + 1 == 2 );
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68 | ok( 2 + 2 == 5 );
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69 |
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70 | from that comes
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71 |
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72 | 1..2
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73 | ok 1
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74 | not ok 2
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75 | # Failed test (test.pl at line 5)
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76 | # Looks like you failed 1 tests of 2.
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77 |
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78 | C<1..2> "I'm going to run two tests." This number is used to ensure
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79 | your test program ran all the way through and didn't die or skip some
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80 | tests. C<ok 1> "The first test passed." C<not ok 2> "The second test
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81 | failed". Test::Simple helpfully prints out some extra commentary about
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82 | your tests.
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83 |
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84 | It's not scary. Come, hold my hand. We're going to give an example
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85 | of testing a module. For our example, we'll be testing a date
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86 | library, B<Date::ICal>. It's on CPAN, so download a copy and follow
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87 | along. [2]
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88 |
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89 |
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90 | =head2 Where to start?
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91 |
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92 | This is the hardest part of testing, where do you start? People often
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93 | get overwhelmed at the apparent enormity of the task of testing a
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94 | whole module. Best place to start is at the beginning. Date::ICal is
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95 | an object-oriented module, and that means you start by making an
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96 | object. So we test C<new()>.
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97 |
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98 | #!/usr/bin/perl -w
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99 |
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100 | use Test::Simple tests => 2;
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101 |
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102 | use Date::ICal;
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103 |
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104 | my $ical = Date::ICal->new; # create an object
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105 | ok( defined $ical ); # check that we got something
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106 | ok( $ical->isa('Date::ICal') ); # and it's the right class
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107 |
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108 | run that and you should get:
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109 |
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110 | 1..2
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111 | ok 1
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112 | ok 2
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113 |
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114 | congratulations, you've written your first useful test.
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115 |
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116 |
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117 | =head2 Names
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118 |
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119 | That output isn't terribly descriptive, is it? When you have two
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120 | tests you can figure out which one is #2, but what if you have 102?
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121 |
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122 | Each test can be given a little descriptive name as the second
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123 | argument to C<ok()>.
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124 |
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125 | use Test::Simple tests => 2;
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126 |
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127 | ok( defined $ical, 'new() returned something' );
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128 | ok( $ical->isa('Date::ICal'), " and it's the right class" );
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129 |
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130 | So now you'd see...
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131 |
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132 | 1..2
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133 | ok 1 - new() returned something
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134 | ok 2 - and it's the right class
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135 |
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136 |
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137 | =head2 Test the manual
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138 |
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139 | Simplest way to build up a decent testing suite is to just test what
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140 | the manual says it does. [3] Let's pull something out of the
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141 | L<Date::ICal/SYNOPSIS> and test that all its bits work.
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142 |
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143 | #!/usr/bin/perl -w
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144 |
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145 | use Test::Simple tests => 8;
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146 |
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147 | use Date::ICal;
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148 |
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149 | $ical = Date::ICal->new( year => 1964, month => 10, day => 16,
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150 | hour => 16, min => 12, sec => 47,
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151 | tz => '0530' );
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152 |
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153 | ok( defined $ical, 'new() returned something' );
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154 | ok( $ical->isa('Date::ICal'), " and it's the right class" );
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155 | ok( $ical->sec == 47, ' sec()' );
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156 | ok( $ical->min == 12, ' min()' );
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157 | ok( $ical->hour == 16, ' hour()' );
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158 | ok( $ical->day == 17, ' day()' );
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159 | ok( $ical->month == 10, ' month()' );
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160 | ok( $ical->year == 1964, ' year()' );
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161 |
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162 | run that and you get:
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163 |
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164 | 1..8
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165 | ok 1 - new() returned something
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166 | ok 2 - and it's the right class
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167 | ok 3 - sec()
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168 | ok 4 - min()
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169 | ok 5 - hour()
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170 | not ok 6 - day()
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171 | # Failed test (- at line 16)
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172 | ok 7 - month()
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173 | ok 8 - year()
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174 | # Looks like you failed 1 tests of 8.
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175 |
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176 | Whoops, a failure! [4] Test::Simple helpfully lets us know on what line
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177 | the failure occurred, but not much else. We were supposed to get 17,
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178 | but we didn't. What did we get?? Dunno. We'll have to re-run the
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179 | test in the debugger or throw in some print statements to find out.
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180 |
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181 | Instead, we'll switch from B<Test::Simple> to B<Test::More>. B<Test::More>
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182 | does everything B<Test::Simple> does, and more! In fact, Test::More does
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183 | things I<exactly> the way Test::Simple does. You can literally swap
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184 | Test::Simple out and put Test::More in its place. That's just what
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185 | we're going to do.
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186 |
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187 | Test::More does more than Test::Simple. The most important difference
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188 | at this point is it provides more informative ways to say "ok".
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189 | Although you can write almost any test with a generic C<ok()>, it
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190 | can't tell you what went wrong. Instead, we'll use the C<is()>
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191 | function, which lets us declare that something is supposed to be the
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192 | same as something else:
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193 |
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194 | #!/usr/bin/perl -w
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195 |
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196 | use Test::More tests => 8;
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197 |
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198 | use Date::ICal;
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199 |
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200 | $ical = Date::ICal->new( year => 1964, month => 10, day => 16,
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201 | hour => 16, min => 12, sec => 47,
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202 | tz => '0530' );
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203 |
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204 | ok( defined $ical, 'new() returned something' );
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205 | ok( $ical->isa('Date::ICal'), " and it's the right class" );
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206 | is( $ical->sec, 47, ' sec()' );
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207 | is( $ical->min, 12, ' min()' );
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208 | is( $ical->hour, 16, ' hour()' );
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209 | is( $ical->day, 17, ' day()' );
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210 | is( $ical->month, 10, ' month()' );
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211 | is( $ical->year, 1964, ' year()' );
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212 |
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213 | "Is C<$ical-E<gt>sec> 47?" "Is C<$ical-E<gt>min> 12?" With C<is()> in place,
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214 | you get some more information
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215 |
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216 | 1..8
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217 | ok 1 - new() returned something
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218 | ok 2 - and it's the right class
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219 | ok 3 - sec()
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220 | ok 4 - min()
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221 | ok 5 - hour()
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222 | not ok 6 - day()
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223 | # Failed test (- at line 16)
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224 | # got: '16'
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225 | # expected: '17'
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226 | ok 7 - month()
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227 | ok 8 - year()
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228 | # Looks like you failed 1 tests of 8.
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229 |
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230 | letting us know that C<$ical-E<gt>day> returned 16, but we expected 17. A
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231 | quick check shows that the code is working fine, we made a mistake
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232 | when writing up the tests. Just change it to:
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233 |
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234 | is( $ical->day, 16, ' day()' );
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235 |
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236 | and everything works.
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237 |
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238 | So any time you're doing a "this equals that" sort of test, use C<is()>.
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239 | It even works on arrays. The test is always in scalar context, so you
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240 | can test how many elements are in a list this way. [5]
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241 |
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242 | is( @foo, 5, 'foo has 5 elements' );
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243 |
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244 |
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245 | =head2 Sometimes the tests are wrong
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246 |
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247 | Which brings us to a very important lesson. Code has bugs. Tests are
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248 | code. Ergo, tests have bugs. A failing test could mean a bug in the
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249 | code, but don't discount the possibility that the test is wrong.
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250 |
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251 | On the flip side, don't be tempted to prematurely declare a test
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252 | incorrect just because you're having trouble finding the bug.
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253 | Invalidating a test isn't something to be taken lightly, and don't use
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254 | it as a cop out to avoid work.
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255 |
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256 |
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257 | =head2 Testing lots of values
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258 |
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259 | We're going to be wanting to test a lot of dates here, trying to trick
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260 | the code with lots of different edge cases. Does it work before 1970?
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261 | After 2038? Before 1904? Do years after 10,000 give it trouble?
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262 | Does it get leap years right? We could keep repeating the code above,
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263 | or we could set up a little try/expect loop.
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264 |
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265 | use Test::More tests => 32;
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266 | use Date::ICal;
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267 |
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268 | my %ICal_Dates = (
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269 | # An ICal string And the year, month, date
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270 | # hour, minute and second we expect.
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271 | '19971024T120000' => # from the docs.
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272 | [ 1997, 10, 24, 12, 0, 0 ],
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273 | '20390123T232832' => # after the Unix epoch
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274 | [ 2039, 1, 23, 23, 28, 32 ],
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275 | '19671225T000000' => # before the Unix epoch
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276 | [ 1967, 12, 25, 0, 0, 0 ],
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277 | '18990505T232323' => # before the MacOS epoch
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278 | [ 1899, 5, 5, 23, 23, 23 ],
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279 | );
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280 |
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281 |
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282 | while( my($ical_str, $expect) = each %ICal_Dates ) {
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283 | my $ical = Date::ICal->new( ical => $ical_str );
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284 |
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285 | ok( defined $ical, "new(ical => '$ical_str')" );
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286 | ok( $ical->isa('Date::ICal'), " and it's the right class" );
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287 |
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288 | is( $ical->year, $expect->[0], ' year()' );
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289 | is( $ical->month, $expect->[1], ' month()' );
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290 | is( $ical->day, $expect->[2], ' day()' );
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291 | is( $ical->hour, $expect->[3], ' hour()' );
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292 | is( $ical->min, $expect->[4], ' min()' );
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293 | is( $ical->sec, $expect->[5], ' sec()' );
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294 | }
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295 |
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296 | So now we can test bunches of dates by just adding them to
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297 | C<%ICal_Dates>. Now that it's less work to test with more dates, you'll
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298 | be inclined to just throw more in as you think of them.
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299 | Only problem is, every time we add to that we have to keep adjusting
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300 | the C<use Test::More tests =E<gt> ##> line. That can rapidly get
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301 | annoying. There's two ways to make this work better.
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302 |
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303 | First, we can calculate the plan dynamically using the C<plan()>
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304 | function.
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305 |
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306 | use Test::More;
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307 | use Date::ICal;
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308 |
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309 | my %ICal_Dates = (
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310 | ...same as before...
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311 | );
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312 |
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313 | # For each key in the hash we're running 8 tests.
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314 | plan tests => keys %ICal_Dates * 8;
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315 |
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316 | Or to be even more flexible, we use C<no_plan>. This means we're just
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317 | running some tests, don't know how many. [6]
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318 |
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319 | use Test::More 'no_plan'; # instead of tests => 32
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320 |
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321 | now we can just add tests and not have to do all sorts of math to
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322 | figure out how many we're running.
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323 |
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324 |
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325 | =head2 Informative names
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326 |
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327 | Take a look at this line here
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328 |
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329 | ok( defined $ical, "new(ical => '$ical_str')" );
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330 |
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331 | we've added more detail about what we're testing and the ICal string
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332 | itself we're trying out to the name. So you get results like:
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333 |
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334 | ok 25 - new(ical => '19971024T120000')
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335 | ok 26 - and it's the right class
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336 | ok 27 - year()
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337 | ok 28 - month()
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338 | ok 29 - day()
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339 | ok 30 - hour()
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340 | ok 31 - min()
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341 | ok 32 - sec()
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342 |
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343 | if something in there fails, you'll know which one it was and that
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344 | will make tracking down the problem easier. So try to put a bit of
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345 | debugging information into the test names.
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346 |
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347 | Describe what the tests test, to make debugging a failed test easier
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348 | for you or for the next person who runs your test.
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349 |
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350 |
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351 | =head2 Skipping tests
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352 |
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353 | Poking around in the existing Date::ICal tests, I found this in
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354 | F<t/01sanity.t> [7]
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355 |
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356 | #!/usr/bin/perl -w
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357 |
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358 | use Test::More tests => 7;
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359 | use Date::ICal;
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360 |
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361 | # Make sure epoch time is being handled sanely.
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362 | my $t1 = Date::ICal->new( epoch => 0 );
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363 | is( $t1->epoch, 0, "Epoch time of 0" );
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364 |
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365 | # XXX This will only work on unix systems.
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366 | is( $t1->ical, '19700101Z', " epoch to ical" );
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367 |
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368 | is( $t1->year, 1970, " year()" );
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369 | is( $t1->month, 1, " month()" );
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370 | is( $t1->day, 1, " day()" );
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371 |
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372 | # like the tests above, but starting with ical instead of epoch
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373 | my $t2 = Date::ICal->new( ical => '19700101Z' );
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374 | is( $t2->ical, '19700101Z', "Start of epoch in ICal notation" );
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375 |
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376 | is( $t2->epoch, 0, " and back to ICal" );
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377 |
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378 | The beginning of the epoch is different on most non-Unix operating
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379 | systems [8]. Even though Perl smooths out the differences for the most
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380 | part, certain ports do it differently. MacPerl is one off the top of
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381 | my head. [9] We I<know> this will never work on MacOS. So rather than
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382 | just putting a comment in the test, we can explicitly say it's never
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383 | going to work and skip the test.
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384 |
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385 | use Test::More tests => 7;
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386 | use Date::ICal;
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387 |
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388 | # Make sure epoch time is being handled sanely.
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389 | my $t1 = Date::ICal->new( epoch => 0 );
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390 | is( $t1->epoch, 0, "Epoch time of 0" );
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391 |
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392 | SKIP: {
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393 | skip('epoch to ICal not working on MacOS', 6)
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394 | if $^O eq 'MacOS';
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395 |
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396 | is( $t1->ical, '19700101Z', " epoch to ical" );
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397 |
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398 | is( $t1->year, 1970, " year()" );
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399 | is( $t1->month, 1, " month()" );
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400 | is( $t1->day, 1, " day()" );
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401 |
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402 | # like the tests above, but starting with ical instead of epoch
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403 | my $t2 = Date::ICal->new( ical => '19700101Z' );
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404 | is( $t2->ical, '19700101Z', "Start of epoch in ICal notation" );
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405 |
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406 | is( $t2->epoch, 0, " and back to ICal" );
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407 | }
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408 |
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409 | A little bit of magic happens here. When running on anything but
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410 | MacOS, all the tests run normally. But when on MacOS, C<skip()> causes
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411 | the entire contents of the SKIP block to be jumped over. It's never
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412 | run. Instead, it prints special output that tells Test::Harness that
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413 | the tests have been skipped.
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414 |
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415 | 1..7
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416 | ok 1 - Epoch time of 0
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417 | ok 2 # skip epoch to ICal not working on MacOS
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418 | ok 3 # skip epoch to ICal not working on MacOS
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419 | ok 4 # skip epoch to ICal not working on MacOS
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420 | ok 5 # skip epoch to ICal not working on MacOS
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421 | ok 6 # skip epoch to ICal not working on MacOS
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422 | ok 7 # skip epoch to ICal not working on MacOS
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423 |
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424 | This means your tests won't fail on MacOS. This means less emails
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425 | from MacPerl users telling you about failing tests that you know will
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426 | never work. You've got to be careful with skip tests. These are for
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427 | tests which don't work and I<never will>. It is not for skipping
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428 | genuine bugs (we'll get to that in a moment).
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429 |
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430 | The tests are wholly and completely skipped. [10] This will work.
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431 |
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432 | SKIP: {
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433 | skip("I don't wanna die!");
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434 |
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435 | die, die, die, die, die;
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436 | }
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437 |
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438 |
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439 | =head2 Todo tests
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440 |
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441 | Thumbing through the Date::ICal man page, I came across this:
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442 |
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443 | ical
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444 |
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445 | $ical_string = $ical->ical;
|
---|
446 |
|
---|
447 | Retrieves, or sets, the date on the object, using any
|
---|
448 | valid ICal date/time string.
|
---|
449 |
|
---|
450 | "Retrieves or sets". Hmmm, didn't see a test for using C<ical()> to set
|
---|
451 | the date in the Date::ICal test suite. So I'll write one.
|
---|
452 |
|
---|
453 | use Test::More tests => 1;
|
---|
454 | use Date::ICal;
|
---|
455 |
|
---|
456 | my $ical = Date::ICal->new;
|
---|
457 | $ical->ical('20201231Z');
|
---|
458 | is( $ical->ical, '20201231Z', 'Setting via ical()' );
|
---|
459 |
|
---|
460 | run that and I get
|
---|
461 |
|
---|
462 | 1..1
|
---|
463 | not ok 1 - Setting via ical()
|
---|
464 | # Failed test (- at line 6)
|
---|
465 | # got: '20010814T233649Z'
|
---|
466 | # expected: '20201231Z'
|
---|
467 | # Looks like you failed 1 tests of 1.
|
---|
468 |
|
---|
469 | Whoops! Looks like it's unimplemented. Let's assume we don't have
|
---|
470 | the time to fix this. [11] Normally, you'd just comment out the test
|
---|
471 | and put a note in a todo list somewhere. Instead, we're going to
|
---|
472 | explicitly state "this test will fail" by wrapping it in a C<TODO> block.
|
---|
473 |
|
---|
474 | use Test::More tests => 1;
|
---|
475 |
|
---|
476 | TODO: {
|
---|
477 | local $TODO = 'ical($ical) not yet implemented';
|
---|
478 |
|
---|
479 | my $ical = Date::ICal->new;
|
---|
480 | $ical->ical('20201231Z');
|
---|
481 |
|
---|
482 | is( $ical->ical, '20201231Z', 'Setting via ical()' );
|
---|
483 | }
|
---|
484 |
|
---|
485 | Now when you run, it's a little different:
|
---|
486 |
|
---|
487 | 1..1
|
---|
488 | not ok 1 - Setting via ical() # TODO ical($ical) not yet implemented
|
---|
489 | # got: '20010822T201551Z'
|
---|
490 | # expected: '20201231Z'
|
---|
491 |
|
---|
492 | Test::More doesn't say "Looks like you failed 1 tests of 1". That '#
|
---|
493 | TODO' tells Test::Harness "this is supposed to fail" and it treats a
|
---|
494 | failure as a successful test. So you can write tests even before
|
---|
495 | you've fixed the underlying code.
|
---|
496 |
|
---|
497 | If a TODO test passes, Test::Harness will report it "UNEXPECTEDLY
|
---|
498 | SUCCEEDED". When that happens, you simply remove the TODO block with
|
---|
499 | C<local $TODO> and turn it into a real test.
|
---|
500 |
|
---|
501 |
|
---|
502 | =head2 Testing with taint mode.
|
---|
503 |
|
---|
504 | Taint mode is a funny thing. It's the globalest of all global
|
---|
505 | features. Once you turn it on, it affects I<all> code in your program
|
---|
506 | and I<all> modules used (and all the modules they use). If a single
|
---|
507 | piece of code isn't taint clean, the whole thing explodes. With that
|
---|
508 | in mind, it's very important to ensure your module works under taint
|
---|
509 | mode.
|
---|
510 |
|
---|
511 | It's very simple to have your tests run under taint mode. Just throw
|
---|
512 | a C<-T> into the C<#!> line. Test::Harness will read the switches
|
---|
513 | in C<#!> and use them to run your tests.
|
---|
514 |
|
---|
515 | #!/usr/bin/perl -Tw
|
---|
516 |
|
---|
517 | ...test normally here...
|
---|
518 |
|
---|
519 | So when you say C<make test> it will be run with taint mode and
|
---|
520 | warnings on.
|
---|
521 |
|
---|
522 |
|
---|
523 | =head1 FOOTNOTES
|
---|
524 |
|
---|
525 | =over 4
|
---|
526 |
|
---|
527 | =item 1
|
---|
528 |
|
---|
529 | The first number doesn't really mean anything, but it has to be 1.
|
---|
530 | It's the second number that's important.
|
---|
531 |
|
---|
532 | =item 2
|
---|
533 |
|
---|
534 | For those following along at home, I'm using version 1.31. It has
|
---|
535 | some bugs, which is good -- we'll uncover them with our tests.
|
---|
536 |
|
---|
537 | =item 3
|
---|
538 |
|
---|
539 | You can actually take this one step further and test the manual
|
---|
540 | itself. Have a look at B<Test::Inline> (formerly B<Pod::Tests>).
|
---|
541 |
|
---|
542 | =item 4
|
---|
543 |
|
---|
544 | Yes, there's a mistake in the test suite. What! Me, contrived?
|
---|
545 |
|
---|
546 | =item 5
|
---|
547 |
|
---|
548 | We'll get to testing the contents of lists later.
|
---|
549 |
|
---|
550 | =item 6
|
---|
551 |
|
---|
552 | But what happens if your test program dies halfway through?! Since we
|
---|
553 | didn't say how many tests we're going to run, how can we know it
|
---|
554 | failed? No problem, Test::More employs some magic to catch that death
|
---|
555 | and turn the test into a failure, even if every test passed up to that
|
---|
556 | point.
|
---|
557 |
|
---|
558 | =item 7
|
---|
559 |
|
---|
560 | I cleaned it up a little.
|
---|
561 |
|
---|
562 | =item 8
|
---|
563 |
|
---|
564 | Most Operating Systems record time as the number of seconds since a
|
---|
565 | certain date. This date is the beginning of the epoch. Unix's starts
|
---|
566 | at midnight January 1st, 1970 GMT.
|
---|
567 |
|
---|
568 | =item 9
|
---|
569 |
|
---|
570 | MacOS's epoch is midnight January 1st, 1904. VMS's is midnight,
|
---|
571 | November 17th, 1858, but vmsperl emulates the Unix epoch so it's not a
|
---|
572 | problem.
|
---|
573 |
|
---|
574 | =item 10
|
---|
575 |
|
---|
576 | As long as the code inside the SKIP block at least compiles. Please
|
---|
577 | don't ask how. No, it's not a filter.
|
---|
578 |
|
---|
579 | =item 11
|
---|
580 |
|
---|
581 | Do NOT be tempted to use TODO tests as a way to avoid fixing simple
|
---|
582 | bugs!
|
---|
583 |
|
---|
584 | =back
|
---|
585 |
|
---|
586 | =head1 AUTHORS
|
---|
587 |
|
---|
588 | Michael G Schwern E<lt>[email protected]<gt> and the perl-qa dancers!
|
---|
589 |
|
---|
590 | =head1 COPYRIGHT
|
---|
591 |
|
---|
592 | Copyright 2001 by Michael G Schwern E<lt>[email protected]<gt>.
|
---|
593 |
|
---|
594 | This documentation is free; you can redistribute it and/or modify it
|
---|
595 | under the same terms as Perl itself.
|
---|
596 |
|
---|
597 | Irrespective of its distribution, all code examples in these files
|
---|
598 | are hereby placed into the public domain. You are permitted and
|
---|
599 | encouraged to use this code in your own programs for fun
|
---|
600 | or for profit as you see fit. A simple comment in the code giving
|
---|
601 | credit would be courteous but is not required.
|
---|
602 |
|
---|
603 | =cut
|
---|